Our DIY Heat Pump Install – Free Heating and Cooling for Life?

A work of art.

To most of the Internet, Mr. Money Mustache is known as the quirky early retirement financial guy, and this is a blog about Money.

But really, I’m not a finance guy – someone who devotes most of his time to optimizing money. I’m more of a general Life Engineer – someone who tries to optimize everything that is fun and interesting in life, and money is just one of those things.

Optimizing means getting the most good out of something – whether it is money, time, health or happiness, while minimizing waste. This is what allows us to make win/win decisions (for example things that make you richer and healthier and happier), rather than win/lose compromises (giving up something you actually like, just to save or earn more money)

One of these win/win things for me has always been optimizing my own houses and buildings to be more comfortable and stylish, while costing less to own and maintain and heat and cool. After all, out of all possible decisions, your choice of home may have the biggest effect on both your financial and emotional wellbeing. Get a reasonable house that is close to your friends and your work, and you’re off to a great start.

 So anyway, this past summer all my favorite factors of optimizing, learning, effort, saving shit-tons of money and reducing loads of waste and pollution came together in the form of a DIY Heat Pump Installation on our commercial building downtown, the home of MMM HQ Coworking.

Why Are Heat Pumps Super Exciting?

Heat pumps are a technology that has recently jumped into prime time and are about to change everything about houses, just as the iPhone did to the tech industry about twelve years ago and just like electric cars are doing to transportation right now. The reason is that they have these fundamental advantages:

  • Heat pumps do the double-duty of heating and cooling any building way better than our existing systems do, but with only one machine.
  • They are super easy to install, and way cheaper to run. They also allow houses and buildings to be constructed more cheaply (less materials and labor).
  • They eliminate a big part of the world’s pollution that is caused by burning oil or gas for heat (as long as you get your electricity from clean sources).
  • And yes, nowadays they work in virtually all climates (down to -20F / -29C): tech improvements have shattered the old limitation where they only worked in places without a real winter. 

How Does a Heat Pump Magically Suck Heat Out of Cold Air? 

Heat pumps save money and energy because they aren’t generating heat directly like an old electric baseboard heater. They are mostly just  moving heat around – from inside to outside in the summer, and from outside to inside in winter. 

To many people, that second situation sounds like magic, but that’s just because of our skewed perception as human beings – a creature that evolved in the warm tropics of the planet Earth. Really, there is plenty of heat even in winter air – if you view it through the Eyes of Physics:

Every spot on our life-nourishing Earth has loads of heat energy (Kelvins), which means it’s easy to harvest some of it.

So, a modern heat pump can easily suck loads of heat even out of air that feels cold to your skin. It does it like this:

Summer vs. Winter modes of a heat pump. The key to everything – fridges, A/Cs and heat pumps – is that the refrigerant gas gives off heat (gets hot) when you compress it, and absorbs heat (gets cold) when you expand it.

You know what else does this exact same trick? Your own FREEZER! Those things typically maintain an inside temperature of about -10F, which means that somehow it is sucking heat out of the air even at sub-zero temperatures, pumping it out to the coils underneath with a fan blowing past them. And if you put your hand there to feel that airflow, what do you feel? Warmth! 

Show Me The Money

Here’s our gas bill history – Yuck! Most significant is the fact that the monthly fee-for-nothing ALONE had risen to $40. $480 per year before you even get any heat out of it!

Before we get into the real details, check out the quick numbers for the heat pump I just installed. Note that I live in Colorado, which has lots of heat and a moderate amount of cold – right about what you’d expect from our position halfway between Maine and California.

  • Cost of the system including all install materials: About $4500
  • My building’s previous annual gas bill: $951
  • Our new annual electric bill for heating and cooling (estimated): $275
  • Annual savings: $676

Annual return on investment (ROI) rate: 15%


Even better: That $275 annual figure for our electricity consumption is what we would have paid, if we had to buy all our electricity off the grid at 10 cents per kWh. But since we generate a surplus of power from our DIY solar array, our net cost is much less than that.

You could even say that all of our heating and cooling is “free” on an ongoing basis, although we did spend $5000 to build the 5.5 kW solar setup in the first place.

So Is A Heat Pump Really a Do-It-Yourself Project?

Our installation team celebrates at the end of a successful project. To be fair, Mr. 1500 and I are both pretty experienced tradesmen, but this felt like a relatively easy project to us.

In a word: Yes, if you are a fairly competent do-it-yourselfer, and you choose a DIY-friendly heat pump kit. It is considerably easier than installing a gas furnace or a metal roof, but not as easy as putting together IKEA furniture. 

Our first install took about 16 person-hours of work for the main job (two people working a full day). Plus I spent about another sixteen dusty hours upgrading the duct work and building custom metal shapes to route the air because our coworking building was so old that the original asbestos-and-mouse-shit ducts were just not worth keeping.

Hmm.. Okay yeah I think I’ll go ahead and replace these ducts.

The value of doing it yourself is that furnace work is one of the biggest returns on your time as a homeowner. Where I live, even a gas furnace + air conditioner replacement can cost $10,000. And although a heat pump hardware only costs about the same amount as conventional furnace+AC ($4000), the companies like to charge more for the newer stuff (or even worse, try to convince you that you’re stupid for even asking about it!).

In other words, even conservatively speaking, for a basic installation you are saving about $6000 in exchange for doing that 16 hours of work, which amounts to a solid $375 per hour.

But Wait! Don’t forget about Rebates!

Even if you’re not a tinkerer, there are some good programs out there that will help subsidize the cost of an upgrade like this. The US EPA offers federal tax credits for lots of things including heat pumps, and local agencies have their own programs – for example neighboring Fort Collins will chip in $2200 towards a unit like ours, which could cover most of the cost of a professional installation.


So if you are ready to upgrade to a heat pump, you either need an honest HVAC company who will install a reasonably-priced machine for you and charge you a reasonable hourly rate. Or, you need to flex your Money Mustache Muscles on the project and do it yourself.

Of course, I chose the latter approach as always, so let’s get into the details of our install!

Step One: Pick a Heat Pump

There are two things you’re looking for here: physical size and heat output. 

The size and shape of indoor portion (the air handler) of the new system have to be similar to your old furnace, or you need to have a plan for how to adapt the new one to blow into your old pipes. As you’ll see below, I chose to do the adapting.

As for the heat output, old furnace was a “100,000 BTU” unit, which is a measure of the amount of natural gas it can suck in and burn each hour. Since it was only about 75% efficient, the heat output was about 75,000 BTU (the real units here are the archaic “British Thermal Units Per Hour”, but all you really need to know is that this is still more than enough to keep our leaky, sprawling 2400 square foot brick building warm easily through even the coldest winters.)

In the most extreme situation (for us this would be a 24-hour period where the temperature is barely above 0F, and it typically does happen at least once every few years), I measured that our old furnace was running for about 8 hours per day, which means our average heat loss was about 25,000 BTU on a continuous basis (75k multiplied by ⅓ of the total hours in a day)

On the cooling side, we had virtually no air conditioning. Just a few crappy portable units scattered throughout the building, with a total combined cooling power of about 20,000 BTU. This wasn’t quite enough to beat the heat in the event of a fully occupied building on a 100F day.

The solution for me was thus pretty simple: the biggest Mr. Cool “Universal” combined heat/cool system, which I started conveniently seeing Google ads for everywhere once I started my research. This beauty is good for about 60,000 BTU of both heating and cooling, which could also be expressed in the even more archaic form of “5 tons”

So I bought the circled option above. In my case, I placed the order through Home Depot website, with the free “ship to store” option, but you could also try your local Lowe’s, Alpine Home Air is good, and Ingrams now sells this unit (including the required 25 ft lineset) through Amazon.

Step Two: Remove your old furnace

This part was pretty easy – except carrying this old block of iron out of the basement.

Safety tip: Make sure you turn off both the gas and electric supply to your furnace before messing with it, as well as opening some windows and running a fan to clear out any remnants of gas as you disconnect pipes.

But once you have it safely disabled, it is as simple as carefully un-wrenching, unscrewing, and cutting away parts of the old furnace (while carefully preserving your existing ductwork) until you have the old one fully removed. You can sell or give it away on Craigslist, or drop off for free at a metal recycling facility. 

Farewell old furnace, may your steel find a fun new life somewhere else.

Step Two: adapt the ductwork as needed

Top Left: an output air adapter box I made to channel the air out to the right places. Right: A prefab filter/input box I bought off of my neighbor (who is also a builder). Bottom: You can see where the two things fit into place along with the horizontally installed heat pump air handler.

If you’re lucky (the old furnace and new heat pump are almost the same size), this step will be easy. You just connect the return ductwork to the bottom of the machine, and the supply ducts to the top. However, I was not lucky.

Because our basement ceiling is so low, I had to install the heat pump horizontally (it is designed to allow this), and then build some adapters to allow the air to flow the way I needed. On top of that, most of our ducts were falling apart and poorly shaped and useless – so I repaired or replaced a bunch of them while I was in the process. This took a lot of work, but my biggest allies were a huge roll of wide, reinforced silver tape, and simple sheet metal tools like shears, angle grinder, self-piercing screws, a good breathing mask, headlamp and work gloves.

Here’s yet another adapter I made to channel some of the air supply. The curvy box below was salvaged from the old ductwork, but I added the end cap and two 7″ air outputs to break this stream of air off to serve two different parts of the building.

Step Three: Fit in the new heat pump

Duct fitting in progress. Okay, I admit this is looking a bit patchy, but it works great! Work like this is a tradeoff between time, cost, and beauty. Since this is in an old building that is probably going to be demolished and replaced with a luxury mixed-use apartment complex when we sell it, I try to keep things functional but simple. In a high-end, permanent house, you’d take more time to make the ducts pretty.

Aside from the fact that the thing is heavy (ours was around 250 pounds), this connection is surprisingly easy once you have the ducts ready. You just screw and seal the sheet metal boxes to the bottom and the top of the heat pump. And at this point, you should be getting excited because the end is in sight.

Step Four: Place the Outdoor Unit Where You Want It

Since the outdoor unit is another 300 pounds, you’ll want a high quality dolly and some ratcheting straps, as well as a strong friend nearby to help you wrangle it into place. Your goal is to put this thing somewhere beside your house that is out of the way, but also close to wherever you just put the air handler in the basement. Then you need a lineset that is long enough to connect them together – and shorter is generally better for both cost and performance reasons (we used a 35 footer). 

We put our condenser on a couple of sturdy, level concrete pads.

Step Five: Run the Lineset

You need about a 4″ hole in your house in order to feed through the insulated lineset. Since our building is made of brick, I needed this crazy masonry core bit – hopefully yours is easier! NOTE: this is an in-progress pic, later I covered these lines with a protective steel box.

The lineset is a pair of flexible copper tubes that are wrapped in insulation. They are bulky, so even our 35-foot set came in a BIG roll the size of a big-screen television box. You need to carefully unroll and straighten it, and feed it in through a roughly 4” hole you drill in the side of your house so you can connect the condenser outside to the air handler unit inside. 

We had the added challenge of having to punch through an eight-inch-thick BRICK WALL, so I had to spend some good workout time wrestling with this massive concrete core driller, mounted to a high-torque low speed drill.

Wrenching on the lineset before releasing the gas (and then testing for leaks). There are just two nuts at each side of the line.

Once the lineset is in position, the connection is refreshingly easy: you carefully follow the instructions to tighten on the right nuts with a wrench, open some valves with an alan key, and you will hear the refreshing PSSSSssssssshhhhh as the refrigerant is released into the system. (This is the part that an HVAC technician would normally have to do, Mr. Cool gets around the issue by using special valves and having pre-charged linesets. More expensive, but very much worth it for the time and labor savings!)

Final Step: Run the Electrical Wires

Drilling a hole for the electrical wire (which we ran in a conduit, the new 40-amp breaker, inside unit wiring including thermostat, Carl celebrates completion of the outdoor unit wiring.

This will vary depending on the system, but ours called for the following wiring, which I subcontracted out to my partner Mr. 1500:

  • A 40 amp / 240 volt circuit to the outdoor unit (which simply means running a length of 8 gauge wire and adding a 40 amp breaker to the box).
  • A 20 amp / 240 volt circuit to the main unit
  • Standard six conductor thermostat wire between indoor and outdoor units
  • And finally, a run of the same thermostat wire between the indoor unit and your thermostat. We took the opportunity to upgrade to the super-lovely Ecobee Lite smart wifi thermostat, which I now use (and love) in all my projects.

The Victory Lap: Fire It Up!

It’s Alive!

We cranked through all of these steps carefully and then flipped on the breakers with great fanfare: SUCCESS! – The Ecobee lit up and started guiding us through its setup screens. Once complete, we slid the desired temperature way down in hopes of experiencing some much-needed Air Conditioning on this hot July day.

And nothing happened. We ran out to the outdoor unit and found it was just sitting there, with LEDs illuminated but nothing else happening.

We both started sweating bullets. Had we made a foolish mistake and bought a faulty unit? Did we screw something up in the install?

Nope – it turns out there is simply a three-minute delay between that first activation and the time Mr. Cool starts his cooling. Very slowly and with great grace, the big fan blades began to rotate, graaaaadually speeding up, with the hum of the compressor so quiet in the background that I had to press my ear up to the thing just to verify that it was really working.

But boy was it ever working – we ran inside and found that that icy cold air was just blasting out of each of the seven large vents spread throughout our building, and baking hot air was now shooting out of the outdoor unit. We had instantly beat the summer heat and everybody inside raised a cheer to this new luxury.

Epilogue, Three Months Later: How Well Does It Work?

A scene from The Extraordinary Event, a weekend-long set of talks and classes featuring Rebel Business School founders Alan and Katie Donogan. Videos coming soon on my Youtube Channel!

Throughout the rest of the summer, we have had a lot of fun putting this system through its paces, and it has proven itself to be an incredible cooling machine. We had several events with over fifty hot bodies packed in for some of our entrepreneurship and social gatherings while outdoor temperatures were in the 90s – and we were able to maintain comfort effortlessly.

The next test will of course be the winter. Here in early October, we have just turned the corner where the building has required just a bit of heat to start some mornings. With a few taps on the Ecobee phone app, I was able to flip the system over to heating mode and give it a whirl. It worked great – heating the building quickly and quietly.

But I’ll update this article over time as we move through cooler seasons. I expect it to continue to perform just great – but it will be fun to verify and reassuring to skeptics out there once we see it with our own eyes.

Extra Cool Detail: How Much Electricity Does It Use?

Screenshots from the Emporia energy tracker app

Of course, being MMM I was not content to just sit back and soak in the cool breeze of accomplishment just yet. I needed one final bit of data – a record of just how much energy this heat pump was sucking down in both heating and cooling modes, so we can get a better estimate of how much money it is saving us over the years. 

So I installed a system called the Emporia Energy Monitor into the circuit panel, which is currently the best value on the market for such a well-designed gadget. This allows me to track and record the full details of the energy flow – through every circuit in the house if I choose to do so. For now, I just have it watching over the heat pump.

What I found is that in cooling mode, the Mr. Cool uses about 2600 watts on an ongoing basis (about the same as two large window air conditioners), which translates to 26 cents per hour of electricity. On the hottest days with the most people, I found the system ran about six hours, meaning our peak electricity use was only about $1.50 per day!

To me, this was pretty remarkable – this was a 95 degree day with 50 people in the building, roughly equivalent to trying to cool a mid-sized restaurant in Texas. Yet even if we repeated this extreme situation every day, we’d rack up an air conditioning bill of only about $45.00 per month!

I found that the heating mode was a bit more thirsty, with consumption at 4000 watts, or 40 cents per hour. Based on my earlier estimates of heat loss on the coldest possible days, we could be in for about 18 hours of runtime per day, which would be $7.20 of electricity. So, if the Headquarters were moved to an extremely cold climate and plunged into neverending 0F / -18C conditions for an entire month (which would make it colder than Duluth Minnesota or Ottawa Canada), we’d still face a heating bill no higher than $210 for the month. But in more realistic conditions for Colorado, we would expect about half of that level of energy consumption. And of course this is only for the month or two of our short cold season. For the rest of the year, heating is even easier.

Conclusion: Heat Pumps Are The Bomb

So there you have it: we dreamed about it for years, finally did it, and I could not be happier. It is such a joy to not even have an account with the gas company, and to know that this part of our expenses will be zero, forever.

And of course it’s even better to know that even the electricity cost numbers in this article are just for your own comparison – in reality, we make more than enough solar electricity run this whole thing for free just from the pretty squares of black glass on the roof. Free heating and cooling for life, with no pollution (with free operation of our laptop computers and beer fridges, and free charging of our electric cars to boot) – This truly is the way of the future!

In The Comments: Do you have any questions about heat pumps or other home efficiency products? And if you have a heat pump of your own, what do you think of it?

  • David Gobel October 5, 2021, 11:20 am

    Cool article MMM. Imagine how much better your results will become when you plug up (almost) all the air leaks in the building! Just did this on our 6000sq ft house and dropped the cfm leakage from over 5000cfm to 3580cfm. This is like closing the door on the refrigerator.

    • Mr. Money Mustache October 5, 2021, 12:00 pm

      Yeah, I have done a lot of that on this building over the years, including upgrading almost every single window and door, spray foam, batts, etc. But it still has plenty of holes, especially in the perforated brick structure of the original pre-1910 house.

    • jimbo November 4, 2021, 2:09 pm

      How do you calculate cfm leakage?

      • John November 27, 2021, 1:04 am

        You block an entry door or a window with a duct connected to a blower made for such tests. Usually done by a contractor that has the equipment and experience to set it up. Some states/municipalities have grants supported in partnership with the utilities company, giving tax credits or other subsidy for insulation and ducting improvements. Those programs sometimes include a measurement of home envelope efficiency with such a blower door test. For a home, it’s usually measured in “air changes per hour” at a given wind speed. Example: 2ACH50 (2 air changes per hour when envelope has sustained 50 mph wind exposure.)

        • Cody Scott January 27, 2022, 8:53 am

          The 50 in ACH50 is the pressure difference, so it is 2 air exchanges per hour at 50 pascals.

  • Joel October 5, 2021, 11:26 am

    Super cool! This is making me wish my house had ducts instead of a boiler/radiant baseboard heating setup. Thanks for the helpful guide for those wishing to learn about a new process and flex their DIY muscles in the process.

    • Jeff October 5, 2021, 1:36 pm

      No ducts needed. Look up “ductless heat pump” for solutions. Mr Cool makes a DIY one in fact. Ours works really well.

      • Jimmy October 5, 2021, 4:07 pm

        Is this the same as ‘mini splits’? We put these in our ADU and they were fantastic.

        • James October 6, 2021, 8:00 am

          Yes, one and the same. I just installed a 4 zone Mr Cool unit (36k BTU) and also a single zone (12k BTU) unit. Did it myself except for the electrical, which required a run from the garage to the side of the house which I wasn’t comfortable doing myself. Did end up saving alot and it’s way better than the window units. The wall units (condensing units) are very quiet, so you don’t hear anything even with it right above your head. The outdoor units are also very quiet.

        • Efficiency Hobbyist October 6, 2021, 10:02 am

          Ductless doesn’t equal minisplit. The minisplit refers to the outdoor unit. The indoor unit can come in all sorts of shapes/sizes. They make a whole variety of ducted minisplits.

      • fredericka October 6, 2021, 8:00 am

        hi, is the ductless heat pump only for one room?

        • Jeff October 7, 2021, 8:09 pm

          There is practically no limit for heatpump configurations. Ducted, ductless, minisplit, multizone, hot water, central heating, etc.

          I’m currently working on a ground source heatpump, which uses underground heat for heating and cooling a multi-storey building.

      • John In Denver October 6, 2021, 9:39 am

        There is also a company named Artic Heat Pumps that has a hydronic heat pump. This might be good for your radiant baseboard setup. Also, I believe Sanden also has a configuration for baseboard heating with their water heater.

  • Kmbelliott October 5, 2021, 11:35 am

    Double check those flare nuts as you get deeper into heating season. We (carrier) have had problems with them. Make sure you use a torque wrench and follow install instructions. If there’s a leak you’ll see an oil stain nearby.

    Your energy use seems remarkably low. Is that heat pump only and excluding the blower?

    • Mr. Money Mustache October 5, 2021, 11:59 am

      Nope, I put the blower on a sub-panel that is part of that overall 40 amp circuit, so that’s the whole energy usage. And this energy meter is super efficient, sampling both voltage and current at something like 1MHZ so it can accurately account even for loads with a strange power factor. So yeah, I too was surprised at how efficient it is! (at least for air conditioning and warm weather heat pumping. We’ll see how it changes as it gets cooler)

  • Profit Greenly October 5, 2021, 11:54 am

    So glad to see you finally put out a heat pump post and what a post it was. Under $5k for a heat pump is crazy cheap. I will be sharing this article far and wide. The only thing it’s missing is a statement of how many kWh you’re using (more important to me than momentary kW of draw data). Here’s a post of my detailed usage from the first year of my heat pump with a link to a twitter thread that describes the next two if you’re interested in comparing (though mine cost so much more than yours that you will win the ROI battle every day).

    Great note on the gas monthly fee stuff too. $40/month just for gas service is insane, but as more people ditch gas it’s only going to increase. Here’s hoping that everyone can get in the heat pump boat ASAP.


    • Profit Greenly October 5, 2021, 12:25 pm

      Was just thinking about this a bit more and I realized your next building upgrade project is the same as mine, a heat pump water heater. If you’re already thinking in this same direction I have a couple recommendations for you.

      First, look at the Sanden Sanco2. This unit has an outdoor heat exchanger that seems dead simple to install because it contains all its refrigerant and simply pipes hot water back to an indoor tank. The other cool thing about this unit is that it uses CO2 as its refrigerant, so if you do get a refrigerant leak it’s no big deal (meanwhile a pound of the Puron refrigerant my heat pump uses will produce as much global warming as a literal ton of CO2 if it leaks so I’m super careful not to let that happen).

      Alternatively, you can look into a Solar Assisted Heat Pump. These run refrigerant through what is basically a big black radiator mounted in the sun. That radiator lets the refrigerant gets warmed from the sun along with from the outdoor ambient air. That means that during a sunny day at least you’ll get crazy high efficiency from these. It also means that there’s no fan in the exterior unit making noise and eventually requiring service. I’ve also heard that a unit like this can get a 26% solar tax credit to help offset its cost. These are really uncommon in the US so far (I’ve only found them at New England Solar Hot Water in Canton MA and The Radiant Store in Troy NY), but it’d be great to see a U.S. builder willing to test stuff out like yourself get your hands on one and help educate the public about them.

      The ultimate in energy savings would be to pair one of these SAHPs with a phase change heat battery from a company like SunAmp, but those are really only sold in Europe right now and until American utilities really get on board with peak time pricing that reflects their actual costs it won’t make much financial sense here. With one of these though you could charge it up with heat when the sun is bright and your SAHP is super efficient, and then use that heat for a whole day or more without needing to run the SAHP when it’s dark.

      Anyways, enough rambling, as you can see I’m super excited about heat pumps and just so happy that you finally made a post about them. Keep up the great work!

      • carl October 6, 2021, 9:04 am

        Hey ProfitGreenly-

        I have spent a lot of time googling heat pumps, but had never heard of a solar-assisted version. It seems like a no-brainer. I assume that the panel is bypassed when you flip over to AC?

        I love that heat pumps are finally gaining momentum. And while they’re pretty great now, I can’t wait to see what innovation comes along this decade.

      • DS December 10, 2021, 8:52 am

        There was a startup in Ottawa (?) that I read about last year who used a phase change material in a mini-split. Their concept was to store heat in the daytime when the heat pump worked more efficiently (warmer outside temperature) and/or when the electricity rates are lower. I can’t find them anymore. It was supposed to be a real money saver.

  • Glen October 5, 2021, 11:59 am

    So glad you wrote about heat pumps! I wish more people knew that they eliminate emissions AND save money on bills! Electric machinery like this is just inherently more efficient than blowing up fossil fuels. And of course if you install a furnace it will continue emitting pollution for its whole lifetime (15-20 years).

    The non-profit Rewiring America has done some nice write-ups on how electrification is the primary path toward zero emissions and will save money: https://www.rewiringamerica.org/

    Here’s a map of estimated yearly savings for using heat pumps in every county in the US: https://map.rewiringamerica.org/

    And soon heat pumps might be a lot less expensive than furnaces because there’s a bill for big up-front rebates for non-polluting home infrastructure: https://www.rewiringamerica.org/policy/zero-emission-homes-act

    • Lee October 5, 2021, 6:17 pm

      For all the Australians rewiringaustralia.org

  • Chris October 5, 2021, 12:01 pm

    Yes, heat pumps are the bomb! Question: did you consider using a ductless system? I’m attempting a reno with a large section of new extension that has no existing ductwork and I’m wondering if it’s worth it to run ducting through all of that or not.

    • Mr. Money Mustache October 5, 2021, 12:12 pm

      A friend just did a 3-head ductless version of this system in a house that had no ducts. Seems to work great, other than the fact that the wall units are a bit clunky and visible.

      For us, since the building already had air ducts it was far quicker and cleaner just to use those (even though I did have to re-work them quite a bit – not a typical situation)

      • JJ October 5, 2021, 9:38 pm

        To report from a cold part of Montana — ductless minisplit heat pumps are terrific. We have a cold weather fujitsu in an 800 s.f. house that is quite insulated (R40 walls, R80 ceiling) and moderately airtight for an older place (~3 ACH50). We use a single ductless unit that delivers 16k btu/hr as the only heat source. Heating costs for use are ~ $250/year. Once or twice a winter we get 7-10 days of -30 F lows and right around 0 F highs. Coldest so far was -36 F. The thing just keeps chugging along and keeps the place comfortable. Of course below 0 F they are less efficient, but they still work. The place is 36 feet long, and the indoor head is at one end of that 36′ blowing towards the other end. The far bedroom away from the head is regularly 4-6 degrees colder than the room with the head, but it’s a bedroom so is better sleeping anyway.

        greenbuildingadvisor.com is a terrific resource for all things heat pumps.

        • carl October 6, 2021, 9:15 am

          JJ, this is great news since the main knock against heat pumps is cold weather efficiency.

          How old is your unit and off the top of your head, do you know the COP?

          • JJ October 6, 2021, 10:28 am

            carl — This was from 2016, the Fujitsu AOU12RLS3H as the outside unit, paired with a single indoor unit, the ASU12RLS3H. For fujitsu, you’re looking for the Halycyon XLTH (extra low temp heating) series. SEER value is 29.3 and COP for heating is 4.64 kW/kW. At the time of purchase it was among the most efficient units available, but that was 5 years ago. I’m not sure if fujitsu or Mitsubishi have come up with better units in the meantime.

            • carl October 9, 2021, 8:09 am

              Hi JJ, thanks for the detailed response!

              I’ve heard great things about Fujitsu, but unfortunately, I don’t think they make a ducted solution, only mini-splits. Please let me know if I’ve missed it!

          • Chris October 22, 2021, 7:51 am

            Another vote for cold weather heat pumps — we have one in Nova Scotia and it works great. We just moved here last year and they seem to be getting VERY popular here. We moved in with one, our neighbor across the street and our neighbor next door just added them. We have a Fujitsu Halcyon. Based on the paperwork, it’s 5 years old.

  • Chris October 5, 2021, 12:09 pm


    • Alistair Twiname October 12, 2021, 3:33 pm

      Then Warm!

  • Ms. Must-stash October 5, 2021, 12:11 pm


    Reporting live from Northern Virginia, where we already have a heat pump and solar panels (just over 7 KW) and now I am longing for a heat pump hot water heater. We have determined from watching consumption spikes from the solar panel monitoring system that most of our excess energy usage these days (above and beyond what we generate from our small townhouse rooftop system) is from hot water usage. And if the claims I have read are correct, we would get 3-4x energy efficiency from a heat pump hot water heater and a payback within 2-3 years….

    • Mr. Money Mustache October 5, 2021, 12:18 pm

      Cool MMM!

      I agree that if you use a lot of hot water in a house, a heat pump water heater is the best solution (as long as you have somewhere to put it that is outside of your main thermal envelope yet not subject to freezing weather – in other words, maybe a non-freezing garage?)

      I’ve run the numbers for my own house (and climate with freezing winters), and we use so little that it’s far better to just get a simple, compact electric water heater once I cancel the gas service. The unit itself is about $1000 less, which is many years of hot water heating, plus it’s way more compact so I save precious garage space (priceless).

      Plus, my electric choices (solar and/or wind) are both 100% clean energy here, so it’s mainly a financial decision rather than a pollution-based one.

      • ZeroGBuff October 6, 2021, 12:22 am

        First off, hooray for heat pumps! I’m dreaming of ending gas service to my house someday…

        Currently, I’m in the middle of getting a heat pump water heater in my townhome that lacks a basement, meaning that utilities are in a small closet on the first floor. It turns out to be a pretty standard thing to duct the cold “exhaust” outside (or, what will most likely happen in my case, up to the attic). I also need to have electricity routed from the panel to the utility closet. Between everything, quotes are coming in ~$6k (~$1500 of that being for electrical + ducting). Not cheap, but my city, county, and utility all have rebates in addition to the federal tax credit.

        If you’re considering installing a HPWH in your living space, definitely check the noise levels. AO Smith units are pretty loud, while Rheem are much quieter. One contractor warned me that Rheem units aren’t as quiet as the company claims, but rather are about as loud as a refrigerator, which makes sense!

        Good luck with whatever you decide to do. I’m looking forward to having gas-free hot water soon!

        • carl October 6, 2021, 9:18 am

          “It turns out to be a pretty standard thing to duct the cold “exhaust” outside (or, what will most likely happen in my case, up to the attic).”

          I wonder if anyone has thought of duct the cold exhaust into the building’s HVAC in the summer to give an assist to the AC? You could have a bipass you flip over in the summer.

          • ZeroGBuff October 6, 2021, 1:24 pm

            I thought about that too. In my case, it probably isn’t worth the added expense, but if I had the DIY skills, I’d go for it!

          • Random doctor October 13, 2021, 6:23 am

            The exhaust is only cold when the internal unit is blowing warm air (as you would want in winter). When the system is running in reverse to cool the internal air (in summer), the exhaust is warm.

            It would be counter productive to pipe the exhaust into the same building that you were trying to heat or cool, since the exhaust temperature is the opposite of the temperature you are trying to achieve indoors.

        • Icetug November 18, 2021, 11:58 am

          Heat pump water heaters looks great on paper, but they have a terrible reliability problem. Chasing a few bucks of monthly savings is a chump’s game when the thing breaks down and nobody will fix it or it needs a total replacement. If you can’t put the unit in an environment that is relatively warm for free (ie non-freezing garage or basement) you won’t actually save anything. You will just be taking heat from your building interior that you paid to warm and using electricity to heat your water. Cost of 50 gallon HPWH, $1200 vs. cost of electric at $500. Supposedly you will save $480 a year in energy. The thing will need to run for 1.5 years before you save anything! Don’t believe that 10 year warranty either, not worth the paper it is written on.

          • Mr. Money Mustache November 19, 2021, 11:51 am

            DUDE! You just proved the case for those heaters in the process of disparaging them: 1.5 years is a PHENOMENALLY fast payback for anything. Heck, even 7 years would be fantastic. It helps to express the payback as an annual percentage return on investment instead. A 7 year “payback” is (1/7) = 14.3% annual return, which is better than any other reliable investment you’ll ever find. A 1.5 year investment is (1/1.5) = 67% annual return!!

            Your other points are well-taken, however: a heat pump water heater is not too useful in a climate that has long freezing winters and requires mostly heat and very little A/C. However, the majority of the Earth’s population lives in warmer climates than this. Reliability, just like any fridge or A/C unit, is not infinite so you should amortize the unit’s extra cost over its 10-15 year lifetime.

            Do you have any data sources (links) to share for the reliability numbers on various brands of heat pump water heaters? Anecdotes aren’t too useful in making decisions.

    • Profit Greenly October 5, 2021, 12:28 pm

      Great to hear you’re looking into a heat pump water heater. I am too, and wrote a rather long, detailed comment on it above for MMM about them (though I hear his response down here about using so little hot water that it’s just not worth the price for). For you though it might make sense. Check out my comment above and get inspired!

  • W Dean Pulley October 5, 2021, 12:14 pm

    In our Southwest Florida home, we ditched the old behemoth central cooling separate condenser and air handling units for cheap, efficient, quiet mini-split units. NO ductwork to gather scropulous effluvia, we only cool the area that needs cooling, and (having de-centralized the system) a potential quirk in one does not disable the others.

    About $400/12K BTU, we DIY installed five in our 3,000 sf home that we’ve hacked into three living units.
    $2K spent, along with $200 to an HVAC tech buddy to pump the pressure down in the empty lines and release the coolant.

    As we run fresh sub-tropics trade winds through our home whenever possible, they don’t get anything like constant use.

    Subvert that paradigm!

    • Johnny Ro October 5, 2021, 5:09 pm

      The wonderful air in Florida is a really good point. Open windows for me within wide bounds. Naples.

  • Physician On FIRE October 5, 2021, 12:19 pm

    I’m familiar with geothermal heat pumps, and this seems similar, but more simple. There’s no need to run a loop deep down underground.

    I’d be curious to know how this setup compares and contrasts with a heat pump using the cool 55 degree F subterranean space as a source for heat transfer.

    We plan to build next year, that is, we plan to pay someone to build us a house, so this is a timely post for us.


    • Mr. Money Mustache October 5, 2021, 12:24 pm

      Good question, Physician! The geothermal (aka “water pipe that you bury a few feet underground”) heat pump systems are far more expensive, but in some cases you may get that money back in the form of higher efficiency, especially in places with an extremely cold winter. Because you’re extracting heat from a 55F source, rather than a potentially 0F or below source, and a similar advantage in the summer.

      However, energy is cheap and labor is expensive. So as long as you have a clean source of electricity where you live, it’s strictly a financial decision.

      It may well be wiser to spend $10k on an air source heating and cooling system, vs. $30k on a ground source system, even if it means your utility bills are $200 higher per year. (In this scenario you’d only be getting a 1% annual return on investment for the extra $20k spent.)

      Final note: geothermal systems were invented in an era where air source heat pumps simply didn’t work in cold climates. So they may well be obsolete now for residential uses.

      • Profit Greenly October 5, 2021, 12:31 pm

        Totally agree, air source has gotten so good that ground source is outmoded in all but the coldest places. Even in those spots ground source may not be best, because you need to run an extra long pipe to ensure your home doesn’t literally freeze the ground it’s trying to extract so much heat from. Generally it seems better to put the money into super insulating such a home rather than building a super price GSHP, but if you’re doing new construction and already have a digger on site it might still be able to pencil out in a very cold climate..

      • Catprog October 11, 2021, 3:59 am

        I have no idea why geothermal is so expensive. All you need is a water pipe and a small excavator to bury it and now you can run water through the pipe and get the energy out/in of the fround

        • mpusto October 14, 2021, 2:38 pm

          Just got geothermal myself. When you can do a horizontal loop it is far cheaper than a vertical system. If you have 40ft of frontage (easier in rural areas) then yes, just dig a ditch and put some coils and you’re set. We didn’t have the frontage without going onto our neighbor’s property, so we had to have a well driller truck out. Drilled 3 wells 240 ft deep each. Those trucks are ridiculously expensive and are booked solid drilling (water) wells for people in rural areas. We live in Wisconsin though, so get a bit colder than CO and air source isn’t rated low enough for us.

  • Another Joel October 5, 2021, 12:36 pm

    I think you probably could have gone with a 4-ton unit (in the spirit of optimizing). Seems like your heating calcs show that it could be done, and 48,000 btus of cooling would be plenty too.

    • Mr. Money Mustache October 5, 2021, 12:45 pm

      Yeah! I figured “Better safe than sorry” for this first experimental installation, but if we are way overpowered, I’ll get a smaller one for my house.

      Also, this 5-ton system has a DIP switch setting you can select where it will self-limit itself to 4-ton (48000 BTU) operation and supposedly give you an efficiency boost as a result. We are on 5 mode right now, but I’ll see how it goes throughout the winter. In summer, I’m already confident that we have way more than we need.

      • Efficiency Hobbyist October 5, 2021, 2:49 pm

        This is a helpful way of estimating load: the insight is that your gas meter has done all the work for you, you just plug in climate data. Other online load calculators have so many moving parts they’re mostly useless or they’re so simple (sqft multiplied by some random number) that they can’t account for building variation.


  • CapitalistRoader October 5, 2021, 12:54 pm

    I have no recent experience with heat pumps. Maybe they’ve improved a lot in the past ten years. I had a rental house in St. George, Utah, where the winter temp very rarely drops below 20°F. It was heated and cooled with a ten-year-old heat pump and did fine until the ambient temp dropped below freezing. There was natgas available on the street so I paid the local utility to pipe gas to the front of the house and install a meter. They did that either for free or for some nominal (~$50) charge. Then I paid an HVAC contractor about $5K to pipe the gas into the house and install a dual fuel heat pump/natgas furnace. It worked really well. It had a thermostat that showed the fuel source being used and typically when the temp dropped below 28° it would switch at least part time to natgas, going to 100% natgas when the temp dropped to 20°.

    It sounds like heat pumps have improved since then and work better when it gets very cold out.

    • carl October 6, 2021, 10:04 am

      Yep, they’ve come way up. Check out the previous commenter from Montana who has a Fujitsu unit.

      St. George is a beautiful area. I’ve been to Brian Head many times and made myself sick from the massive shakes at Iceberg!

  • Girija Unnikrishnan-Rema October 5, 2021, 1:01 pm

    Another excellent article! My HVAC is approaching end of life and I have been thinking of replacement cost and alternate solutions. Heat pumps is one of my considerations. Your article came out just in time. Thank you!

  • Eric B October 5, 2021, 1:21 pm

    I’ll just throw in my anti-recommendation for Trane systems. I don’t think they sell to individuals anyway (so you can’t DIY), but for how much I spent having it installed, it has some surprising design flaws–like an LCD display that overheats and damages the entire $800 thermostat (unless you crank the screen brightness all the way down, have the screen off most of the time, and don’t let your house get too hot). Even getting the poorly design unit replaced *under warranty* was expensive.

  • tom October 5, 2021, 1:55 pm

    Solar energy isn’t free of pollution. It is LESS pollutey than most other forms of useful energy, but it’s still carbon emissive and the panels themselves are pretty bad to dispose of at end-of-life. Don’t confuse less bad with good or neutral. Solar is just less bad, not good, not even neutral.

    • Catprog October 11, 2021, 4:01 am

      Thin film solar is the one with the nasty chemicals.

      Most of the roofs panels are almost all silicon, glass, aluminum (and their oxides) (A little bit of plastic too)

  • steveark October 5, 2021, 2:00 pm

    I’m not real sure about the recent technology angle. We’ve been in our house for over forty years and it had a heat pump when we moved in. And we are in backwoods Arkansas so its not like we are in some tech zone. The only big drawback is you need a honking big generator to run them in prolonged power failures versus running a natural gas furnace where all the electricity does is spin the fan.

    • Chris B October 6, 2021, 7:19 am

      The savings from not having a gas bill will pay for a honking big generator.
      Perhaps a propane space heater would be a cheaper way to provide backup for outages.

      • steveark October 6, 2021, 2:15 pm

        Actually we’ve got a combination of a natural gas furnace upstairs and a compact split mini heat pump that my generator will run simultaneously, also both gas and electric hot water so we can do just fine in prolonged outages, which aren’t uncommon out in the sticks. We’ve actually got three different HVAC systems in our house, it is a zoned system of sorts.

  • HeavyDinFTC October 5, 2021, 2:03 pm

    Thank you for posting this!! I, too, have been intrigued by the Mr.Cool units.
    Can you confirm if the CT(s) for your power monitoring is only for the compressor or if it is also monitoring the blower?
    Reason I mention: I don’t think the Mr.Cool blowers are variable speed…I believe they are on/off. (while the compressor is variable speed). I’m interested in what the blower draws, as my 90’s era blower pulls a shocking 500+W.
    Other fun hacks might be auto-set the thermostat during peak-hours (in Fort Collins, power is almost 4x the cost during peak). So run it hard while you’re off-peak and lotsa solar then use the “thermal battery” of the building to try and coast during peak-hours. Rock on!

    • Mr. Money Mustache October 5, 2021, 2:43 pm

      I did answer part of this in another comment: my power measurements include both indoor and outdoor units combined.

      But here’s the answer to the other part of your question: because this is a heat/cool combo, I believe the indoor unit has more to it than just a blower. But you CAN run just the fan as well, using the “fan on” option on the thermostat.

      I just did that right now (again from the comfort of home!), and I see that the machine’s power consumption has only gone up by about 120 watts.
      – standby power consumption of the whole system is 40 watts
      – power consumption in fan-only mode is 160 watts.

      This sounds kinda low for a blower that is something like 2000 cubic feet per minute, but maybe fan-only mode runs slower than full heating or cooling mode (?) More investigation needed.

      • HeavyDinFTC October 5, 2021, 3:04 pm

        Thank you for the reply+data! Will be fun to track how it does over the coming months.

    • ek2009 February 7, 2022, 2:32 pm

      I’ve been running 2-3 Ton version of MrCool Universal, and also logging the power consumption data.
      I have dual-zone setup (using EWC zone dampers), and depending on which zone(s) are on, the air-handler consumes around 89-120Watt. The condenser unit is set to 2-ton setting consumes, and depending on outdoor temperature and the return air-temperature can consume anywhere between 1.89KW and all the way to 2.9KW per hour. This latter peak consumption is a very short duration (not more than 5 minutes) during the “dead of the night” when outdoor ambient temperatures drop to 37F (I know, it doesn’t get too cold out here).
      By the way, the outdoor unit even at these temperatures gets frosty sometimes, and during defrost the condenser could rev itself up to about 3.67KW level for about 30-45 seconds. I guess this is why their installation guide recommends specific breaker/fuse sizes.

  • David Sutherland October 5, 2021, 2:18 pm

    Like MMM HQ, our Boulder CO house has photovoltaic solar panels and produces excess electricity. You can sell the extra energy back to Xcel (our provider) but they only give you about 3 cents per kWh versus the 11 cents they charge you for consumption. Thus, finding a way to use all of the electricity you generate is a good financial plan (assuming you’re replacing another energy source like natural gas or gasoline).

    Earlier this year, we replaced our old natural gas water heater with a heat pump water heater, and couldn’t be happier! Our natural gas usage has dropped to 0 for half the year, and we are still not paying for any electricity, so operating costs are essentially zero so far. Winter solar production drops so we will dip into our solar bank to pay for water heating in those months (excess solar production in summer is ‘banked’ for use in winter months). Venting from the heat pump is routed through a damper, so in summer the heat pump provides air conditioning, and in winter months the cold air gets dumped outside.

    There are all kinds of rebates available from the county and city (Boulder) if you go with a certified installer which made a DIY a non-starter. The installed cost for the heater was $3600, but we get half of that back from the rebates as well as federal tax credits. The rebates were super easy to arrange as there is a free service in Colorado called “Energy Smart Colorado” who will take care of all the leg work for you. In the end, we were out of pocket $1800 for a new water heater, which is about $800 more than an installed natural gas heater would have cost. The energy savings will make up for this in only a couple years, so the HP water heater was a no-brainer.

    Obviously, the rebates greatly improved the payback time, so it’s worth checking with your own county/city to see what they offer in your area.

    • carl October 6, 2021, 10:14 am

      “Venting from the heat pump is routed through a damper, so in summer the heat pump provides air conditioning, and in winter months the cold air gets dumped outside.”

      David! I’ve wondered about this very thing (exhausting the air into ducts in summer). This is pretty awesome! In the summer, your heat pump helps out the AC. In the winter, you’re pumping out cool air to assist with climate change! :)

      Would you be willing to provide pictures of your installation with damper setup? Or, I’d love to see your setup in person since I’m right up the road in Longmont. I’ll even buy you a beer! mr1500 at 1500days dot com


  • SR October 5, 2021, 2:30 pm

    I’ve been thinking about getting a minisplit for years, but somehow hadn’t even noticed that there were more DIY friendly ducted ones on the market.
    I wonder if it would be possible to duct one of these up in parallel with a furnace. I think we’ll end up going with a ductless, and keep the furnace for cold spells. We usually get at least a week, sometimes 2 or 3 where the temperature never goes above 0*F, so we’d still need some sort of backup.

  • Chris October 5, 2021, 2:38 pm

    Between the Solar Project, Creative Shed, and your other construction affairs…you’ve really helped both Jenni and myself consider doing more DIY work! Carl / Mr. 1500 has also been such a great source of motivation in that area, too!

    Thanks for putting out this sort of writeup and not just always sticking strictly with money things (as your intro alluded to). It helps us all expand our comfort zones! After all, with copious amounts of retirement time, we each need new projects to roll up our sleeves and get busy with! There’s nothing quite like digging deep, taking a risk, and then looking back at a trail of sweat, time, and just a little blood — a completed *thing* done yourself.

    On the heat pump—
    We’ve got an air handler setup currently in our place in Virginia – a 1920s brick townhouse-like building with 16 other duplicate units around us in a U shape. The heating is a community-shared radiant system with a commercial gas boiler. That boiler is ancient and almost certainly will kick the bucket in the next handful of years. We (the community) have been talking about just switching all of us to individual heating. Lots of our neighbors have already installed their own heat pumps. Our AC/air handler system is from 2006 and this year’s service/inspection showed that there’s probably not a ton of life left in the coils.

    We’re considering joining the chorus of fellow neighboring heat pump owners who seem reasonably satisfied…though I do wonder if we’re not losing something in terms of efficiency by getting rid of the centralized system. Did you run across heavy-duty heat pumps that might work in a commercial application that could hook up to an existing series of water-fed radiators?

    I’m also wondering if we’d personally experience any advantage to using a more modern AC system like this. Our ~1300 sq.ft. is typically about $120/month in summer to keep at 74f with the existing system.

    As always, thanks for the fun rundown MMM!

    • JB October 6, 2021, 10:24 am

      I have a similar situation in my building in Chicago. We have a central boiler (nat gas fed) and cooling tower combo that provide hot and cold water to all 44 units in my building. The system is switched twice per year to deal with the heating and cooling cycles. Each unit has their own water source heat pump to control their own environment. There is a lot of consternation among the owners because water source heat pumps are not the norm in this area and can be quite costly to replace (at least, in terms of labor to remove the old one and install new one). It makes it more of a pain that most of them are installed hanging from 12+ ft ceilings in the units and sometimes are behind drop ceilings or drywall.

      If anyone has a good source of information to compare water source heat pumps that would be greatly appreciated. One thing that concerns me in particular is running noise because the pump is installed inside our living space. I find that I have to turn the TV volume up when our unit is running. The other thing that concerns me is energy use (shocking). I have 2 pumps in my place currently and they run quite a bit in hot/cold months. We do not have access to renewable energy on-site, so we pay for the electricity use and it is not uncommon for my electric bill to crest the $200 mark in high-use months. It would be really nice if I could knock that down a bit.

  • Efficiency Hobbyist October 5, 2021, 2:56 pm

    I recently installed a cold climate heat pump (24,000 Btu). So far (installed in Feb.), it has been about 40% cheaper on a Dollar/Heating Degree Day basis vs. the old gas furnace. With the recent natural gas price increases, those savings will be higher this winter. Comparing AC+Furnace vs. Heat Pump installation prices, the cheapest quote I received was for a heat pump. Comfort wise, I prefer the Heat pump so much more. It’s 1. quieter due to its variable speed blower, 2. can maintain indoor temps much better than the oversized furnace, 3. allows for 24/7 filtration, and 4. doesn’t blow cold air prior to scorching air like the furnace did.

    • carl October 6, 2021, 10:16 am

      Which brand/model heat pump did you go with?

      • Efficiency Hobbyist October 6, 2021, 1:18 pm

        Mitsubishi Cold Climate 24k Btu high static unit. COP of about 3.5-4 so far.

        • Yonghan Ching October 6, 2021, 1:41 pm

          DId you DIY or have a contractor install it for you?

          • Efficiency Hobbyist October 7, 2021, 8:53 am

            Contractor, I wanted a pro. Maybe prices are geographically different, but the cheapest heat pump quote I got was $6k. The Mitsubishi was about $3k over that.

  • Eric W October 5, 2021, 2:57 pm

    Next time you rip out an old furnace/air handler, grab the blower fan from it and build your own DIY Blower door tester: https://www.builditsolar.com/Projects/Conservation/BlowerDoor/BlowerDoor.htm

  • Alex October 5, 2021, 3:05 pm

    Is there any info you can send me about how you built your 5kw solar array? I’m thinking about doing this but my math came out to about 4k$ for a 3.5 kw not including the battery.

    • Mr. Money Mustache October 5, 2021, 4:52 pm

      I sure do have more info for you (it was also linked in the article but I know there are a LOT of links in there!)

      As for cost, you are right – while the base equipment for a 5kw system has a wholesale cost of less than $4000 these days, it all depends on how much markup the supplier is adding. So far, the market for solar panels and inverters is kind of wild and inconvenient, because there are not enough DIY folks like ourselves out there to attract bigger retailers.

      As for battery storage – those are not too useful where I live so mine is just a grid-tied system. But in areas with fluctuating power prices and big blackouts (like Texas last year, Hawaii, California), it’s a great idea and Tesla Powerwall is the best system at a reasonably competitive price.

  • Retired at 45 October 5, 2021, 3:25 pm

    Thanks for the great write-up! I agree with a previous commenter that your unit is probably oversized, but between the DIY install and running it off cheap solar, getting a right-sized unit probably wouldn’t have saved you much money. Keep on plugging those leaks to improve comfort and save on operating costs!

    For readers looking for a comprehensive overview of heat pumps and many other aspects of converting your home or small commercial space into an efficient, comfortable, fossil-free, happy place, I highly recommend the detailed series of Electrify Everything videos by Nate Adams. I have no affiliation with him except for being a happy consumer of his educational materials! See http://bit.ly/EEincourse to sign up for the video series.

  • Roberto October 5, 2021, 6:19 pm

    There is literally zero chance I would ever embark in this kind of complicated endeavor and risk my life in the process due to my extreme incompatibility with skilled labor. So this post should have been of no interest to me right? Wrong, I was totally riveted and couldn’t put it down until finished. Super interesting

  • Adrian Utsch October 5, 2021, 6:22 pm

    Hi MMM,
    Thanks for another amazing article. I am concerned that one of your depictions of your ducting shows what looks to be old asbestos tape. Asbestos of any kind is a serious hazard and any disturbance of asbestos products usually requires professional abatement companies. Wearing a respirator is not enough because if you remove asbestos tape you can send particles all over the place. I also think you should have MMM diy’ people understand how carcinogenic asbestos is and not to underestimate how dangerous diy removal of asbestos products can be if they want to upgrade their duct work or remove old stuff that has asbestos tape etc. Be well

    • Mr. Money Mustache October 5, 2021, 6:37 pm

      It’s good to be aware of the risks of asbestos – but also not to have an unrealistic fear of the stuff, as I think the building regulations seem to have adopted (expensive professional mitigations even for a few scraps of it, etc) https://www.unco.edu/facilities/services/environmental-health-and-safety/pdf/When-is-Asbestos-Dangerous.pdf

      When you read the history of why it is considered such a big deal in this country, it sounds like past lawsuits relating to chronic exposure played a big part – there wasn’t really an issue with short, passing exposure to people during renovations (especially if they are being careful).

      Wearing a proper two-cartridge respirator system (preferably with full face shield) does indeed protect you from virtually all airborne particles right down to the virus level of size, and even organic vapors, and it’s a good idea to wear this for ALL dusty/nasty work including spraypainting, insulation work, etc.

      For asbestos, I’ll leave it up to each person’s individual comfort levels, but I think the key to avoid endangering yourself and others is to leave the stuff intact (rather than peeling or breaking it), keep the work area well-ventilated, and dispose of it in a sturdy sealed bag.

      • Mark October 8, 2021, 12:45 am

        Bound versus umbound asbestos is the big difference. Bound example: asbestos containing sine wave shaped roof? Unbound example: asbestos tape/ The roof panels are fine to remove with some minimal precautions like using a mask and spraying shaving foam on the screws before unscrewing, and as you say, sealed bags to dispose of them. The unbound variant I wouldn’t touch with a ten foot pole….

        • Mr. Money Mustache October 8, 2021, 12:25 pm

          Okay, I’m definitely open to being even more careful – but can you direct me to some studies that I can read that will help me quantify the risk of each different situation? I need numbers in order to make decisions, rather than just hardline yes-no rules.

          • Darrin October 12, 2021, 6:54 am

            Long time lurker; first comment…I must be in a talkative mood this morning. I’ve always enjoyed your lifestyle and especially your construction articles. Thank you for sharing.

            Regarding the asbestos comments: it’s like my physics professor said when discussing quantification, “How is important to know but how much defines what will kill you, because everything can.” Delightful class.

          • Alistair Twiname October 12, 2021, 3:52 pm

            it is very hard to get numbers because asbestosis takes so long to kick in (the numbers of people dying due to asbestos is still rising in the UK for example. ) but i’d back up mark simply because it’s the difference between it being airbourne or not.. which is obviously when it’s dangerous. given you are working next to ductwork that will run into the spaces of people who aren’t masked I think it’s worth the extra care. plus not all asbestos is the same stuff. https://www.mesothelioma.com/asbestos-exposure/types-of-asbestos/ You are quite correct though that normally it’s just best to leave it where it is. but if you are removing it do everything you can to stop it becoming airbourne.

  • Reade October 5, 2021, 6:29 pm

    Hey MMM, that basement looks kind of low. Is the next project going to be a dig out and underpinning? IT would certainly increase your useable space, increasing the overall value of the building. The ROI could be massive if you could DIY. I realize that’s a pretty big job.

  • Ben October 5, 2021, 6:38 pm

    I’ve lived in Florida most of my life, and always had a heat pump. I was surprised to learn that many places never used them. The difference between a heat pump and a regular air conditioner is a single valve. It probably costs a couple bucks. Why are any AC’s that aren’t heat pumps still sold?

  • Kevin Bridges October 5, 2021, 6:43 pm

    Hey MMM, I really enjoyed seeing all of the details related to your heat pump install. I would love to see you write more on your blog. These types of articles are super useful, and often inspire others to act. We are in the process of having 30 solar panels installed on our roof here in the mountains of southern Utah, where we enjoy 300+ days of sunshine a year. Our heating system is natural gas, and original with house (built in 1996). Our house is at 8,000 feet elevation, so we don’t have or need AC (a few days a year it gets warm in the afternoon, but it’s not bad). With the solar panels, converting as much as possible to our new clean electricity is a huge win. Three rooms in the house have electric heated floors, so we plan to crank those during the winter days when the sun is out. We also have a hot tub with an electric heater, so we plan to schedule the heater to stay on all day, and shut down at night. Now you have me thinking that we should look into a heat pump and a heat pump water heater. If we balance our net metering properly, we can practically run everything in this house from just solar. Thanks!

  • Douglas E Sprague October 5, 2021, 7:05 pm

    I am looking forward to replacing the forced hot air oil furnace in the house I just bought and am renovating in RI, its 1100 sq ft of living space, has an old rusty oil tank and is begging to be replaced. This will give me the motivation to make it happen. I am doubtful I will have the cost efficiency but to do away with the oil, maintenance, and chimney will be fantastic, and to boot have central AC!!

    • Efficiency Hobbyist October 6, 2021, 9:31 am

      You’ll be surprised – oil is about as expensive a way to heat as there is. Even with high Northeast electricity rates, you’ll probably be cheaper per Btu.

  • Clay October 5, 2021, 8:07 pm

    I installed the exact same Mr Cool 4/5 ton heatpump last winter. My house is similar to yours a 2600 sqft 1950’s brick ranch but with insulation upgrades, as such I use it in 4 ton mode. It has been an excellent system that I highly recommend. At the exhaust registers I’m getting 102 F degrees from heat and 56 F degrees in cooling. My only suggestion to the lineset install is to lightly use Nylog Gasket/Thread Sealant, tighten the connection, let it set a day or two for expansion and contraction, then retighten the lineset connection before opening the refrigerant valve. It’s been solid for me. From my research on minisplits, the most common problem was leaks at the lineset connection. Just like you I found it an easy project but time consuming, took around 3 days by myself to fully install. It does require research before starting for wiring, lineset planning, duct connection/mastic. After install, using a infrared thermometer to find air leaks in the older insulation wrapped ducts solved our “dustly” house issue. Thanks for a great article!

    • carl October 6, 2021, 10:49 am

      Hey Clay, where in the world are you? Since we just installed it, we haven’t had much chance to assess the cold-weather performance. I’d be curious to know how much the 102 dropped off in severe cold.

  • Rowan October 5, 2021, 8:52 pm

    Awesome article. We replaced an LPG (propane in American) hot water tank with a CO2 heat pump, it costs 75% less to run, I only wish we could divert all the cold air from the pump into the house in summer, which is what I thought you might try in reverse? In summer you could heat water with waste heat being pumped out of the building.

    • carl October 6, 2021, 10:50 am

      “I only wish we could divert all the cold air from the pump into the house in summer”

      Why can’t you?

  • lukebuz October 5, 2021, 8:54 pm

    Did you really just use my 338/FSK insulation sealing tape on your metal ductwork?
    At minimum, you should use a foil tape, and better yet a mastic foil tape. For commercial use, UL cert is best.

    Expect failure of tape joints in a few years, if you just use a metalized paper tape!

    • Mr. Money Mustache October 5, 2021, 9:57 pm

      Is it really YOUR tape Luke? If so, congratulations, I LOVE this stuff!

      Whatever this is (I got it from an engineer friend’s factory buildout project) seems to be all metal when I cut through it, other than the fiber reinforcements. But even that 338/FSK stuff says it’s good to 200F, way hotter than a duct would get – is there really a problem?

      Either way, thanks for the caution, I’ll keep an eye on it over the years. Like everything in life, this just another fun science experiment!

      • lukebuz October 7, 2021, 9:20 pm

        Yeah, still a working stiff. Looks like mine, glad you like it! Product Manager for HVAC tapes. The tape is just a kraft paper with super thin foil laminated with scrim reinforcement. FSK = foil, scrim, kraft. Meant to seal foil backed insulation, doesn’t have strength (tensile or adhesive) to hold up for years on ductwork. Keep eye on it!

  • DIYrentalGUY October 5, 2021, 9:05 pm

    Awesome! I installed the SAME system in my home in April – a 3 ton Mrcool Universal and just finally got around to posting about it last week on IG. Our 1929 home in Pittsburgh had radiant heat and no air conditioning, which means that I also had to run all new ductwork (flex duct mostly). That was fun. A lot of time crawling around in the attic.

    I really must thank you MMM! I started following you in 2014 and it has made a huge difference in my life. My confidence to figure things out and do things that are physically and mentally hard (badassity) has been building and building over the last 7 years, so I think it’s pretty cool that our projects coincided like this.

    Make sure Mr 1500 put a manual disconnect service box near the outside condenser! In my area code requires it.

  • Canuck Rick October 5, 2021, 11:36 pm

    Seems doable, but I recently purchased (house hacking) a 100 year old house with radiators and boiler powered by oil. Yuck. Any ideas on how to keep the radiators Cause they add to the charm and character of house with the beautiful hard wood floors (and heat is nicer than dry heat from ducts). A Ductless heat pump won’t fly cause those things on the walls in a character house wouldn’t be smart from an asthetic/re-sale perspective in my opinion. Not sure there is an option for heat pump via radiator/boiler system? I was told convert to gas boiler but although efficient, and cheap over here on west coast, I want to say away from fossil fuels.

    • Efficiency Hobbyist October 6, 2021, 9:34 am

      This is a major obstacle for heat pumps: there are very few options for air-to-water. Adding ducting should be the most practical way to do this. Geothermal can make hot water, but there goes your investment return.

    • EfficiencyNerd October 6, 2021, 10:46 am

      As Efficiency Hobbyist mentioned (quality name btw), there are unfortunately very few air-to-water heat pump options. In my mind, however, hydronic heating with radiators is actually a better and more efficient heat delivery system than forced air – a small water pump uses a lot less energy than a blower fan, and you can have individual room control via thermostatic valves on the radiators. Water carries heat much better than air. Also, as you mentioned, the heat is much nicer than dry heat from ducts. It’s unfortunate there aren’t more air-to-water heat pumps, but there are a few – here is a great write-up of one such setup: https://www.greenbuildingadvisor.com/article/air-to-water-heat-pump-retrofit

      • Henry Chinery October 6, 2021, 11:37 am

        All heated air has lower relative humidity, whether from a heat pump, wood stove or radiator. Since the outside air is cold and holds fewer grains of water per cubic foot, heating lowers the relative humidity. Humidity/moisture must be added back to the air to increase comfort. This can be through an in-dict humidifier in a forced air system, pots/pans of water on tops of wood stoves or radiators or whatever else you can think of. Radiators don’t humidify the air they heat.

    • ChrisD November 27, 2021, 12:36 pm

      In the UK we all have radiators running off water heated by a gas boiler (in the cities). Aparently gas boilers will be outlawed in 10 years time, and I do assume that whatever heat pumps we have will be expected to work with the same radiator/water system. So maybe wait a few years and import one from Europe?

  • ZeroGBuff October 6, 2021, 12:30 am

    Thanks for the article, MMM! I’m watching closely and thinking of switching to a heat pump in the near future. I have a question, though: does your heat pump have an additional electric heating function? I asked a contractor about heat pump systems, and he told me that the straight heat pump only works down to about 20 F. After that, there’s an electric heater that extends the range down to -5 F.

    I’m down the road from you in Boulder, and we do get the occasional week below 20 F, so I’ll be curious to see how your system handles a cold snap.

    • Efficiency Hobbyist October 6, 2021, 9:37 am

      That contractor is not the contractor you want working on your home. There are heat pumps that work down to about -20. LG, Mitsubishi, Fujitsu, etc. make cold climate models. Adding resistance backup heat also works with non-cold climate models. They aren’t limited to -5, they have no outdoor limit, so I’m not sure why they’d tell you that unless they push gas.

      • ZeroGBuff October 6, 2021, 1:35 pm

        Interesting…thanks for the tip! As mentioned above, I’m doing the water heater right now but have mentioned the other project to bidding contractors in case there’s an opportunity for synergy between the two systems (answer appears to be mostly no). Since the EnergySmart program limits me to contractors on their list, I might hold off a bit to let them “discover” those cold-weather models while doing my own research.

    • Heat pump curious January 14, 2022, 2:07 pm

      I was just told the exact same thing by a heating contractor in Boulder. They said that a heat pump with resistance backup heat would add $250-550 per month to our electricity bill in winter as the resistance backup would kick-in so frequently. I was surprised and frustrated they couldn’t narrow down that $300 range more precisely. Their alternative was to suggest a gas furnace backup at an additional installation cost of ~$9K. Needless to say I’m going to speak to some other contractors!

    • Scott January 15, 2022, 1:28 pm

      Our Contract said the nearly the exact same thing, below 20 F you have to have backup heat. But his reasoning was not that it wouldn’t work, but that it becomes very inefficient below 20 F. Is that true? And if so, is the idea that it runs so efficiently above 20 F that it makes up for the difference the few times a year it drops below that?

  • Jimmy 持夢 Gottlieb October 6, 2021, 1:05 am

    After suffering 21 years with inefficient and insufficient electric resistance heat, I finally installed a four-head mini-split heat pump two years ago, and I’m only kicking myself for not doing it decades earlier.

    High on the heat pump train, I then purchased a heat pump clothes dryer (though I try to air dry clothes whenever possible).

    Next, I would love to get a heat pump water heater except that my water heater is in the hallway right outside my bedrooms, and heat pump water heaters are not quiet.

  • Schmitt October 6, 2021, 1:19 am

    Hi MMM!
    Thanks a lot for this very detailed description.
    We have been running our heat pump for 19 years now.
    I have made a detailed calculation of the exact energy costs.
    If interested, check my website and search for heat pump.

  • Ishmael October 6, 2021, 5:42 am

    One piece of advice I was offered by a construction friend – look for heat pumps that have a manufacturer’s warranty, not one offered by a third party. The third party ones can have the company offering the warranty go out of business and you’re SOL if the unit fails (which happened to my parents recently).

    They are amazing units, and I’ve long been a fan (had one installed on my house in 2001), but always a good idea to make sure you’re getting one backed by a solid warranty.

  • James October 6, 2021, 6:33 am

    Wow, fantastic write up!

    I knew about DIY minisplits but not diy for a whole house unit.

    Does this run like a minisplit? The compressor runs at max speed until the setpoint is reached and then the compressor slows down to maintain?

  • Brian October 6, 2021, 7:10 am

    This is an amazing project! Please keep this updated as you get some experience with the winter.

    This is very timely for me. I just had a contractor in Denver tell me that heat pumps won’t work here because it’s too cold. Thanks to some good advice on your forums (and this blog post), I now know that this is complete nonsense.

    As much as I love DIY projects, this might be a bit above my level. I’ll probably pay someone to do it for us, but I still expect the payoff to be worthwhile.

    I do recommend connecting the rest of your power monitor. I got one a few months ago, and found out some fascinating things. One of the odd things I found is that my radon fan is sucking down 8% of my electricity usage. Replacing it with an energy star model will pay for itself in about 3 years. I would have never even thought to look at that otherwise.

  • Dan Jarmolowicz October 6, 2021, 7:18 am

    Not sure you need it where you are located, but in Massachusetts the manufacturers recommend installing the outdoor unit on a stand to get the unit out of the snow and because the outdoor unit drips water in the winter (which can refreeze and damage the coil). You may want to add a drain pan heater if winter temperatures stay below 32 F for significant periods of time to protect the coil if the unit didn’t come with one preinstalled. Overall great article.

    One other small note is that although modern refrigerants are ozone safe, they are potent green house gases so for less experienced folks it may be worth calling in a professional to handle the refrigerant side of things. I do have a refrigerant license so maybe I’m biased, but figured it’s worth noting.

    • Mr. Money Mustache October 6, 2021, 9:23 am

      Good tips, thanks Dan!

      I think (but am not sure yet) that our Mr. Cool already has the various heaters it needs to automatically survive winter conditions since it is designed to work down to the -20s.

      As for snow: yes, we do occasionally get some very occasional big dumps and drifts here so I’ll have to shovel this thing out occasionally. There was no reasonable place to raise it up from the ground without it looking crazy and blocking windows, so I figure that the small inconvenience of shoveling is worth it.

  • Jared October 6, 2021, 9:02 am

    My HVAC is 25+ years old so this article is good timing for me considering I might have to replace mine soon!

    One thing I’ve noticed in my house is the hot air doesn’t seem to be as hot once it hits the bedrooms. I’m in a 70s split-level house, so the HVAC lines run between the floors. It also seems like the windows are a little leaky and maybe even the walls too.

    My question is this: I’m not planning on living hear for much longer than 5 years before moving, so would it be worth it to upgrade any of this stuff? The inefficiency bugs the heck out of me but if it’s going to cost a lot more to fix it than I’d get out of it, it doesn’t seem to make sense for me to do it.

  • Sarah October 6, 2021, 9:13 am

    Yessss! This is the type of content that got me hooked on your website years ago. Thank you for sharing!

    I’m your neighbor in Lyons (and I own a rental in Longmont) so I love following your DIYs and how you make decisions for our climate.

    My personal home is a log-built house that currently uses baseboard hot water heat. In the winter I spend on average $500-$600 a month on propane to run the boiler that heats the home (ouch!!!!) I’ve been working on various projects to bring that down (re-caulking windows, putting in thermal curtains, replacing the fireplace inserts) but something like this would be an amazing option, especially since I plan on adding solar in the next couple of years. There is no attic to insulate (vaulted ceilings) so I’m somewhat limited in what I can do to increase the home’s R-value.

    Do you think it would be worth installing a heat pump for a log home that does not have ductwork? The main level of the home is fairly open, with only the master bedroom and bathroom on a separate level. There is also a finished basement that I rent out, but it’s sunk into the stone foundation so it stays pretty temperate.

    • Mr. Money Mustache October 6, 2021, 9:19 am


      Yes, you should buy the biggest ductless mini-split system you can find TODAY and start asking your friends for HVAC installer recommendations to put it in when it arrives. I can’t even believe you have lived in this giant flaming emergency for so long, I think I would have sold a place like that about 30 seconds after seeing the first bill. Propane is NOT a good heat source unless you live in a camper van or other situations where there really is no other option.

      • Sarah October 7, 2021, 9:44 am

        Haha thanks for the reply!

        Last winter was my first winter here, as it is an inherited family home. Fully paid off and on acreage with well water and septic, so that makes up for a lot of its… Quirks. My grandparents mostly heated with pine in the wood fireplace, but I need to do some upgrades on it to make it safe.

        I will start researching ductless mini-split systems.

        Open to recommendations for HVAC installers in the Longmont area! Thanks!

  • Jay October 6, 2021, 9:30 am

    My house has had a heat pump since 1983 (when it was built). When I moved into the house in 2008, the heat pump went out about a year later. I had a new one installed in 2009. THey work fine as an air conditioner during the summer but it has always struggled to heat the house during winter. If you are not careful the electric bill during the winter could easily get over $300/month. If the temp was below 30 F, the thing ran no-stop to try to keep it warmn, and I had the thermostat at 65 – 66 F. If my house had the option of gas heat I would have had it installed. When looking at heat pumps online, they are crazy expensive, around $7000 and up. Not sure how you got yours so cheap, but right now I am not a fan of them.

    • Efficiency Hobbyist October 6, 2021, 9:42 am

      Contractors struggle installing heat pumps. The process of sizing is more involved and they frequently screw it up. That’s not really a knock on heat pumps, more on the installers. It was 100% possible to install the right sized heat pump in 2009. Paradoxically, running 24/7 is actually what you want out of a heat pump (furnace/boiler too), that’s why the most advanced models are variable speed. Constant operation means it’ll be quieter and have more even heat.

    • Henry Chinery October 6, 2021, 11:02 am

      I had a similar situation in my home in Maryland. The problem was that it was never installed properly when the house was built in 1982. They ran the ducts for the upstairs through the outside wall cavities leaving out the insulation in those parts of the exterior wall. Since heat pumps generally only create about a 20°F difference bin air temperature I lost half the effect to the outside of the house before it got to the second floor. It was always hot upstairs in the summer and cold in the winter. They also put huge return grills in the walls but they led to 2″X3″x14.5″ stud cavities severely restricting the return air flow to the air handler in the basement. In 2007, I had the still functioning York 3 ton heat pump replaced with a Carrier Infinity 5 ton variable heat pump. (We had finished the basement increasing the conditioned space). We also had them run new return and supply ducts to the upstairs and remove the ducts in the outside walls. Return and supply ducts and registers were run to each bedroom so they would work even with the doors shut. (They should be closed when sleeping for fire safety). It completely worked! Temperatures were consistent throughout the house no matter what the season. And I didn’t have to lug wood in to keep the wood stove running to heat the house overnight. Tract home builders generally cut costs to maximize profit knowing that most people don’t have a clue. Before the internet it was especially difficult to find out.

      • Ginger October 17, 2021, 7:51 pm

        I live in Maryland and was looking at heat pumps. What company did the work in 2007? I’d be interested in getting the recommendation.

    • Scott October 6, 2021, 12:52 pm

      This has been my experience with a new heat pump in Utah, as well. I got it thinking I’d be seeing a significant reduction of heating costs in the winter, and yet the whole unit inside and out would run for over 4 hours every morning just to get to the same temp it would take my normal gas furnace an hour to hit. I’ll give it another look this winter to see if anything changes, but once I realized the stupid thing was basically constantly running and my electric bill was crazy high and I was just wearing out all the mechanicals faster, I flipped it over to Emergency Heat mode to bypass the heat pump and just go back to regular gas heating. I also have an electricity monitor tied to the panel, so I can check my actual usage from that specific source.

      • Efficiency Hobbyist October 6, 2021, 1:23 pm

        Constant operation (for variable capacity systems) is most efficient when running at a lower speed. That means setbacks don’t save you money. Ideally, you’d have long run times at a constant setpoint. It’s unexpected, but long run times at lower capacity are the most efficient. It’s due to the physics.

  • No More Weekdays October 6, 2021, 10:09 am

    Great post on heat pumps. I’ve wanted one for years. We currently heat with natural gas and use window units for AC so the central air alone would make for a huge upgrade. We also have solar with excess production so our heat pump should effectively run “for free”.

    The main reason we haven’t gotten a heat pump already is that we’ve been told by multiple HVAC people that our duct work would need to be completely replaced (unless we went ductless). The reason being, our runs off of the main trunk lines are all very small, only 3” diameter. Supposedly that’s fine for heat but would cause issues with cooling. I can’t tell if that’s HVAC boogeyman talk to try and upsell or how much of that is real. When I google duct sizing info it gets really technical really fast.

    What are your thoughts / experience with duct sizing and heat pump? Is it really finicky or is “close enough” good enough?

    • Henry Chinery October 6, 2021, 11:25 am

      Forced hot air ducts had more fudge factor due to the higher temperature levels being put through them. But if you switch to a heat pump they may be inadequate for the temperatures produced by a heat pump, generally 15°-20° F from return air temperatures. So no, he probably wasn’t blowing smoke. HVAC systems are complicated especially when structures are changed by air sealing, increased insulation, high efficiency replacement doors and windows which affect the size of the heat pump needed to condition the space. Many jurisdictions require the contractor to do a load calculation to determine how much heating and cooling capacity is actually needed. It’s actually better to undersize the system than to oversize it. And there are calculations to determine optimal duct sizing and routing to properly condition all spaces. I didn’t notice any mention of a load calculation being done in the article so the system may be oversized. That may cause the system to not remove enough humidity from the air during cooling season making people field cold and clammy. A trained HVAC technician does all these calculations based on upgrades, expected/variable occupancy, correcting deficiencies due to previous poor installation, wear and tear on the system, changes in the structure and type of occupancy etc. Yes, it looks easy but it’s not as easy as it looks. Do you want to read the internet and remove your own gall bladder or do you want a trained experienced surgeon to do it for you? There are standards HVAC contractors are supposed to adhere to and large complicated books from organizations like ACCA to tell them how to do it. So can you replace your own heat pump? Sure. Should you? That’s a question you should decide for yourself. Sometimes, it’s just way better to spend your time researching to find a competent professional and pay them to do the job right the first time. Good luck to you.

    • Efficiency Hobbyist October 7, 2021, 9:01 am

      It’s hard to say without a room by room cooling load calculation. Heating will likely be fine – often furnaces are 2-4x oversized, so using a lower heating air temp is fine. Also, insulated ducts for the supply ducts would prevent cooling condensation, which is necessary.

  • Half-Stached October 6, 2021, 11:36 am

    Wow – this article has perfect timing! After the heatwaves this summer, we’ve decided that we would install a heat pump in our condo in Seattle. We currently have gas heating and no AC. Due to being in a condo, our options are bit more limited and I think we’re going to need to go with a mini-split. However, I’d love to leverage any experience or suggestions people have before we make any purchases. Most information I’ve seen relates to houses – what do we need to take into account for installing a heat pump in a condo?

  • Yonghan Ching October 6, 2021, 2:05 pm

    I so wanting to get rid of my 1970s 100k BTU/h gas furnace and replace it with a heat pump!

    However, in the Twin Cities MN, things can and do get extremely cold. We had a cold snap of -40F (-60F with windchill) few years ago and I am concerned that a ccASHP is still not going to make it.

    Therefore I am leaning toward a hybrid gas/ccASHP system, where the gas furnace would only work during the very cold days.

    Do you see any flaw in my thinking?

    • Efficiency Hobbyist October 7, 2021, 9:08 am

      Hybrids work great. You can save a lot of gas that way, the distribution of heating load is skewed towards mild temperatures, even in MN. It’s also beneficial because MN will have lower cooling loads vs. heating loads, so you can right size for AC. You really don’t want to oversize AC equipment
      Since you have an existing furnace, dig up some old bills and try this:

      What you’d be looking for is the heat load line. If it’s close enough to a heat pump’s output and you have sufficient electric panel room, you may be able to get by with just electric backup and avoid the furnace.

      • Yonghan Ching October 8, 2021, 8:21 pm

        Cool! I did a very crude Manual J and am not confident with the numbers I got. Thank you for sharing this alternative method. I did a calculation based on the instructions and it come fairly close to my Manual J (29kBTU/h vs 30kBtu/h), assuming my old furnace is at 70% efficiency!

  • Rob October 6, 2021, 2:32 pm

    I have lived in the Midwest my entire life and my previous home had a heat pump for about 10 years. One of the benefits that often isn’t mentioned is just how comfortable your home becomes. These units are desgined for high usage and when the outside temperature drops into the low 40s and below they will run nearly continuously, quietly, and the benefit of this is any chilly spots in your home are eliminated because the air is costantly being moved around and heated.

  • Eliot October 6, 2021, 3:35 pm

    Howdy, New Zealander here.
    Interesting to read how things are done differently in another country. I think what you call “minisplits” would make up 99% of (domestic) heatpumps here. It is unusual to have ducted heating or a “furnace”
    There has been a subsidy available to get rid of open fires and old woodburners and replace them with heatpump (or low emission burners).
    I have to agree that solar PV + heatpump cooling is a great match. I have 1.5kW of PV, and that is plenty to run the house including the heatpump on a low cooling setting.

    When you have to start paying the real price of CO2 emissions in the USA I wonder if gas fired heat will be less appealing?
    Power prices are higher here about 35NZ cents / kWh daytime, 15c night, which makes PV worthwhile.
    (1NZD = 0.68USD)

    • David October 26, 2021, 4:46 pm

      Fellow kiwi here.

      Yeah I think they seem to label them as single split and multi split here.

      I think ducted is increasing becoming more common. Just put one in our new build cost us 12k ( + extra 2k for zoning) through AVS. Absolutely worthwhile for a comfortable house and way cheaper to run than I expected.


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