My DIY Solar Power Setup – Free Energy for Life

It is pretty well known at this point that Mr. Money Mustache is enamored with solar power. Besides the obvious Sci-Fi coolness of it (Electricity, Satellites, Futuristic Robots!) and the eco-friendliness of it (energy with zero noise or pollution), in the last five years the money side of things has finally matured, so that solar power is now the cheapest way to make electricity – even before you account for the added bonus of any available subsidies and the benefits of pollution-free living.

A Watt of Solar Panels: From $100+ to under fifty cents (2017) in less than my lifetime (image source cleantechnica). And the 2017 number for the blue side of the graph hit over 95,000 MW.

It works for individuals: In many cases, if you can get a good rack of solar panels on your roof, your monthly savings will be equivalent to making an investment that performs better than the stock market. But the numbers look even better as your solar setup becomes larger, like if you’re running a solar energy utility or a community solar farm.

Related: In recent Colorado Energy Bids, Solar energy is the cheapest option, even when backed by battery storage (Vox).

The fun part of this for me has always been the physics. Ever since I learned how much energy the Sun shines onto our planet’s surface (about 16,000 times more energy than all of humanity consumes, even with our current bloated habits), I have been certain that a mostly-solar-electric world was inevitable. The only obstructions were human inertia and politics, which are temporary. Physics is forever.

For example, consider the following map showing the tiny amount of our deserts we would need to cover with solar panels to replace all energy consumption (electricity, oil, gas, nuclear, hydro, wind, etc)

Fig. 1: Tiny land area required to power all of humanity. (image source)

And it’s actually even better than that: the image above assumes an old-school solar panel efficiency of 8%, whereas 18% is now a standard rate. So you can cut the black dots in half again, and then chop a few more times to account for the other existing clean energy sources.

And of course, you don’t have to concentrate the panels and run giant power lines everywhere as implied by the map. You can stick solar panels virtually anywhere and they will start working like little employees for you, tirelessly cranking out energy (which is equivalent to money) automatically.

Which is of course the real subject of this article.

My DIY Solar Project

The new solar array at the MMM HQ workshop generates more than enough power to run the whole property year-round, plus charge the electric cars of the various members.

So naturally, I have always wanted to have my own solar power farm. Until now, various excuses kept me from getting it done: no great places to put panels on the roof of my main house, slightly unfavorable local regulations, but mainly a lack of knowledge of exactly what to buy and how to install it.

I vowed that whenever I finally got this project done, I’d write up a report to you, to spare you some of the research and time consumption that I had to go through.

So let’s get into it!

Part One: Show me the Money

As you can see from the picture above, I’ve started by building a relatively small solar array. There are twelve panels, each about 40 x 60 inches. Each one generates 300 watts of electricity when the sun shines, and when you run the numbers for my climate, the whole setup will crank out about 6100 kWh/year of electricity, a chunk which is worth about $732 per year at average US power prices.

Pretty amazing – enough energy to run my coworking space and Mrs. MM’s adjacent retail store… from a chunk of pretty black glass that is about the same size as a single car parking space!

Meanwhile, the wholesale cost of this equipment broke down roughly like this:

  • 12 solar panels at $130 each: $1656 (a total of 3600 watts at 46 cents per watt)
  • 12 Optimizer modules (which increase power output during partial shade): $650
  • One SolarEdge 6 kW Inverter (converts the DC from the panels to AC for the grid): $1102
  • Various brackets, mounting racks, bolts, and wiring stuff: $460

So my total cost, due to the very good luck of having a friend who is both a dedicated Mustachian and the owner of a booming solar company, was $3900.

That’s the best case, but even after you add normal profit margins plus a 30% tariff that The Donald recently levied on solar panels (and remember the panels are thankfully only half the cost of the system), you can still buy a similar Complete kit for $5000 or so.

When you’re measuring the annual return on your investment (or “payback period”), there’s only one thing that matters on the cost side: price per watt. I ended up building this system at about $1.08 per watt, which is low by today’s standards but will soon sound high.

And remember, there are usually tax incentives to cut this cost further  – you can take 30% off the top of this cost due to the US Federal “Investment Tax Credit (ITC)“, and possibly more from your state and local government or utility.

The Great Solar Journey to Durango

Last year, I met a badass Mustachian entrepreneur named John. He was in Longmont to visit some family here, but his real home base is in Durango, Colorado where he runs a successful solar installation company called Shaw Solar. There are a million stories that need to be told about this man, but for now we’ll start with this one.

Knowing how long I had been interested in a do-it-yourself solar project, John decided to step up and help me get it done at last. We went over technical details, calculations, strategies, and costs. All of this culminated in me taking a spectacular roadtrip to Durango along with another local friend, in May of 2017.

It was quite a trip, for much more than the acquisition of solar panels and advice. Durango is a stunning little town, and it turned out that John lives in a community of equally impressive siblings and friends – for example his brother Charles who DIY-renovated a 50,000 square foot school over a 20-year period, which has now become the jewel of Durango’s downtown.

Time For the Build

I drove back from this trip full of confidence and energy… only to end up storing the solar panels for months in my studio building as I worked to finish higher-priority parts of the Headquarters building, then waited for the time and motivation to plow through the building permit application.

It took another visit from John to really kickstart the project, and once we worked through it I realized my worry was completely unfounded – if you know what you’re doing, a simple solar array can be completely installed by two people in a less than a day’s work. Here’s what we ended up doing.

Step Zero: Research and Permit

Begin with the end in mind. The amazing Kari Spotts (LPC’s lead of renewable power metering) helps me swap in a new dual-flow electric meter at the successful completion of this project.

This is the part that stops most people before they even begin. The quickest shortcut is that if you’re not interested in these details, find someone who is, to catapult you through it. But if you have enough curiosity to learn the details, here they are:

How big a system should I build? In general, the bigger, the better. The cost per watt goes down as your system grows, making it a higher annual yield on the investment.

“I don’t live in Colorado. How much juice will I get out of it where I live?” This part is fun: The National Renewable Energy Lab runs a great, free calculator called PVWatts that does it all for you: factoring in average weather and solar angles in your area, even allowing you to specify solar panels placed at any crazy angle you like. (In other words, your house doesn’t have to have a perfect South-facing roof).

“Do I need some of those Tesla Powerwall Batteries too?” No. Unless you’re building an off-the-grid cabin, in almost all cases you will want to “grid-tie” your solar array, so you can effectively sell your surplus electricity back to the power company (and thus, other nearby customers), cleaning up your whole town and saving the huge cost of batteries. The Powerwall works great if you want protection from power outages, however, and can even pay for itself if you live somewhere with a smart grid that allows day/night price arbitrage.

“How do I get a permit to build this thing?” Your city’s building department probably has a page describing how to apply. For example, here’s the one for Longmont. The trickiest part is generating a “one-line diagram”, but I cheated by just photoshopping my own details into the example provided with my city, leading to this result, which they approved without question.

Step One: Layout

I had a nice, simple roof that was already facing South, tilted up at a 30 degree angle, which is just about perfect for solar panels. But you can also put them on other slopes or flat roofs, and they still work surprisingly well.

I needed two rails for each row of panels, and the rails get supported by “L”-shaped brackets bolted into the roof. So I ended up with this configuration:

Laying out support brackets, rails, panels, and power inverter.

Important consideration: Because I was putting this on a garage roof (technically “unoccupied space”), I was able to squeeze them all the way to the roof edge. If you are installing on a house, your city’s fire code may require that you leave a 3 foot walking access around the edges. Sometimes it’s wise to think outside the box: a garage roof, a standalone ground-mounted rack if you have lots of unused land, or creating the new workshop/carport/garden shed you’ve always wanted in the sunniest part of your yard.

2: Install your Brackets and Rails

Once you figure out where to put the long “lines” shown above, you measure them out and snap chalk lines right over top of your existing roof material. Then, use some sturdy 2.5″ lag bolts and washers to hold down the L-shaped brackets that come with the solar racking kit. Pre-drill each hole, and inject in some “Through the Roof” sealant with a normal caulk gun before driving in those bolts – this creates a permanent watertight seal. (There are also special brackets to accommodate different roof styles like tile and metal).

Once the brackets are in, you simply use the supplied slide-in bolts and nuts to attach the long rails, straighten them up nicely, and lock it down. Doing all of this with a cordless impact driver makes it quick and clean.

3: Bolt down and connect the Optimizers if you’ve Got ‘Em

These are just little flat boxes that you connect to the top of each pair of rails, about 6″ from the eventual right edge of each solar panel. There’s one optimizer for each panel, and it acts like a babysitter – monitoring output from the panel, compensating for voltage changes when necessary (such as when shade hits that panel). You’ll notice that each optimizer has four wires protruding from it, and there’s one optimizer for each panel. This will make sense in the next step.

Optimizer mounting (face down), plus a good shot of the connections between roof, brackets, and rails. Note – a solar installer saw this and said he suggests you use flashings like this for extra protection on those L-feet.

Once all the optimizers are in place, you connect each pair of longer wires together with the incredibly convenient fast-click connectors. The positive and negative wires have differently shaped connectors so you can’t accidentally reverse them.

You end up connecting optimizers to each other, and each panel only to its host optimizer, like this:

Inverter to panel connections

If you have two lines of panels as I do, connect the far end of one line to the far end of the next line, so you end up with a long series of optimizers where both ends terminate with a loose wire on the end closest to your inverter.

Grounding is Important: Using the supplied grounding screw terminals, connect all the rails together with bare 10AWG copper wire. From that last terminal, you’ll be running a length of the same size wire down to the inverter.

4: Install the Solar Panels!

The bottom of each panel has two long output wires. Use clips and/or zip ties to keep the cables tidy so they don’t dangle onto the roof too much.

This step is better with two people, especially on a steep roof. Starting at the furthest corner from the location of your inverter, connect each the panel’s wires to the matching ones on its host inverter. Set the panels down straight, and use the click-in clamps that come with the racking system to clamp down the panel using your cordless drill/driver.

By the end of this step, you’ll have one or more tidy lines of panels with just two powerful-looking DC wires poking out the end, with connectors ready to go.

You’re now ready to build the final run of wire, which will enter a metal conduit and travel through your roof, down the side of your house, and into the inverter.

5: The Home Run:

Drill a 1″ hole in your roof and put a roof boot over top of it, tucked under the upper course of shingles. From there, your goal is to provide a protected path to get the high voltage DC wires from the panels, down to the inverter.

My city required 3/4″ metal conduit, which gave me the opportunity to learn about the various fittings and connectors that are part of working with conduit. I also bought a conduit bending tool, since there are many more outdoor electrical projects still on the docket for the MMM HQ building.

I ran a length of metal conduit up from the inverter and just beyond the roof boot, then transitioned to a downward-facing connector to some flexible conduit, just to keep the wires covered until they get under the panels. All three conductors including the ground are running through this tube. If doing it again, I’d suggest using a different conduit box for that transition. Also, you can switch from a bare ground wire to a stranded, insulated ground at that point – much easier to pull through!

6: Mounting The Inverter and Connecting it all to the Grid:

The part that sounds the most mysterious is actually one of the most simple:

  • Hang the inverter on the wall using the supplied bracket and a few screws
  • Connect the conduit and pull in the DC wires from the solar panels into the inverter’s connection box. On this Solaredge unit, there are nice spring clip terminals.
  • Do the same on the other side of the connection box, running a length of 8/3 household wiring (for outputs up to 40 amps) right into the breaker box, as if you were hooking up any other 240 volt circuit.

Inverter mounting, including the conduit going up through the roof (left), out to the main breaker box (right), required warning stickers (red), and how it’s hooked up inside (bottom)

7: Get it all Inspected and Power it Up!

The inspector will probably have a nitpick or two with your work. Stay strong and make any required corrections, and pass that inspection. Then you flip on the AC breaker, the DC power switch, the inverter’s main power switch, and poke through the menu systems to make sure everything is set to run the way you like it.

For this Solaredge system, I had to run a “Pairing” step with the power optimizers (see manual), and add a TP-Link Wireless Repeater/Bridge to allow the inverter’s wired Ethernet connection to join my existing property-wide Wi-Fi network. Which happens to be the the spectacularly good Google Mesh Wi-fi system.

So What’s Next?

From this point on, it’s all on automatic pilot. The system generates electricity every day, which reduces the Headquarters power bill down to zero. In winter, the days are shorter so we might consume more than we produce. But in summer, a large surplus will more than make up for it.

My inverter from Solaredge comes with a really nice monitoring features, available from both a phone app and any browser. Plus, you can share a public version of your page with anyone. Here’s one I made for the MMM-HQ array.

At the time of writing, I’ve had the system online for 27 mostly-January days, including a couple of writeoffs where the panels were covered in snow. It has still averaged about 10 kWh of electricity production per day, which is more than the average consumption of the whole facility. Put another way, the 265 kWh of electricity is enough to power an electric car for roughly 1000 miles of driving.

The monitoring tool also estimates about 410 lbs of CO2 emissions prevented, which is 0.2 tons or about $4.00 worth at current carbon cleanup rates. If you happen to care about running a carbon-neutral life (or business) as I do, this means the carbon offset makes your solar electricity about 15% more valuable in your mental accounting.

I can also double or triple the number of panels on this particular system (once I decide on a good place to put them) without changing the inverter or any of the grid-tie connections, which will greatly improve my annual return on investment. It’s just a LEGO-like plug and play to connect more panels to an existing rack of them, plus the inverter has a second set of inputs if you are running in some wires from a string of panels you have placed somewhere else.

My power company pays out a check for any overall surplus at the end of each year, purchasing the power at a wholesale rate. But many regions are more solar-friendly than this, giving you a full retail or even higher rate for solar-generated electricity as an incentive to go green.

The Final Word:

Solar energy is strangely fun to produce – most people report satisfaction far beyond just the monetary benefits. It gets you out there rooting for the Sun, and for your fellow humankind to follow suit and start harvesting it alongside you. So if you’ve been considering getting it done, the time is good.

Thanks again to John Shaw (shawsolar.com) for all the help with this project. If you have questions about the details or the industry in general, please put them in the comments and both John and I should be able to weigh in.

And if you happen to own a home or business around Durango, CO, contact Shaw Solar directly and tell ’em who sent you!

I also recruited some highly valuable help from an excellent more local electrician : Derek Miller who runs Omni Electric – highly recommended for projects in the Longmont/Boulder/Evans areas.

Rough Edges Alert: I’ve started by publishing this article in an unpolished form, so if you see incorrect details, please let me know and I’ll clean it up over time after publication.

  • Tania February 8, 2018, 11:30 am

    “Physics is forever.”

    Possibly my favorite sentence on this website.

  • Claw February 8, 2018, 11:34 am

    My wife, 2 small kids and I sold the mansion last year, built a smaller house and have been off the grid in Iowa since June 1. The power company wanted 39k to run power to my new house location and that was NOT going to work. After tax credits my 15.6 kw system with batteries and back-up propane generator (installed) came to, you guessed it, 39k. Good, bad or indifferent that’s what it cost and it’s done I have to say upfront that my brain does not have one ounce of engineering capability. That being said I’ve kept this baby running and besides a few programming issues, all is well. 2000 sq. foot house, shop, and barn are all connected. I have a centralized inverter and not micro-inverters so if one of my 48 panels is 80% snow covered then all panels will produce at only 20%. The generator has only ran a couple of times this winter and recharged my batteries within about 4hrs. (2 gallons propane/hr.) I had no idea how much power I was producing last summer….I could have powered a small city. Winter is more fickle but as stated in other replies, cold cloudy days still produce power. I went with lead acid batteries because Tesla wasn’t available. Batteries are good for about 10 years so my options should be good by then. Very little battery maintenance….every couple months they need topped off with distilled water. I could go on but I won’t…..I am happy with the system and have not regrets.

    • Mr. Money Mustache February 8, 2018, 2:12 pm

      That’s a great point – for remote properties, the Tesla / off grid economics suddenly start looking like a huge winner. Burying cables or putting up aerial electrical wires and posts is super-expensive, then you lock in a monthly fee as well. In fact, the monthly fee for my commercial building electric service is high enough that it’s almost worth going off-grid as well – if cost were the only consideration.

  • Trevor February 8, 2018, 11:35 am

    My local power company has instituted additional fees for on-grid solar, which severely extends the payback period. Accordingly, I’ve been exploring a divorced setup consisting of smaller appliances and lighting on solar, with AC and other 240v appliances on-grid. While this doesn’t address the ~$20 monthly maintenance fee (which accounts for approximately 25% of my total annual bill), it will essentially maximize savings while avoiding the additional ~$40-50 monthly fee.

    This obviously requires a powerwall to store energy for use during off-peak (read: evening) hours. So I’ve been building a 48v powerwall using old laptop cells, at a much lower price point than Tesla. All told, it will still be much less than the going rate for professionally-installed panels.

  • Oscar Quintero February 8, 2018, 12:03 pm

    Nice article. Great stuff.

    Are you worried about the perforations (moisture and leaks) and weight on your roof? How do you seal the holes and perforations that you drilled on the roof?

    • Mr. Money Mustache February 8, 2018, 1:53 pm

      No worries! Asphalt shingles are actually pretty leak-resistant, since they are made of a gooey tar that seals around most protrusions. In this case, we also injected “through the roof” sealant as noted in the article, into each drilled hole before driving in the lag bolt.

      Weight of solar panels is negligible compared to what roofs are designed to support.

  • Brian M Feroldi February 8, 2018, 12:28 pm

    Glad to hear you are finally part of the solar club. We electrified our solar system in RI in September and our estimated ROI is 11% annually. Beats the stock market!

  • Rob Lepage February 8, 2018, 12:50 pm

    The IPCC 5th assessment and the EPA provide estimates on the true cost of carbon (social cost of carbon). The true cost of carbon is actually $220-290USD/tonne, which covers all externalities. This can cause powerful change in how you choose to live if you factor in as part of your financial calculations. The ‘extra’ fee you pay, you can collect and divert to organizations and agencies that are trying to move us towards a low-carbon economy. Plus you’ll be prepared when higher carbon taxes come down the line. Everyone wins.

    • Mr. Money Mustache February 8, 2018, 1:50 pm

      Hey Rob, I’ve never heard an estimate THAT high – can you share your source?
      Here’s an EPA website (apparently a saved copy from before before the oil industry took it down?) chart with some estimates:

      Regardless of the social cost (aka damage estimate), you can clean up CO2 for much less than $290 per ton through things like the Amazon Conservation reforesting programs or other things offered through Carbonfund / Terrapass.

  • sarah Shaw February 8, 2018, 12:52 pm

    So cool that you wrote about my brothers!
    They do ROCK in a big way. So proud of them.

  • Eric February 8, 2018, 12:55 pm

    Have you gone to a full electric building? i.e. with heat pump, electric furnace, electric stove and electric water heater? I don’t know if it would make sense cost-wise to turn over a gas furnace and water heater.

    Instead we are air sealing and insulating to grab the lower hanging fruit and get 12-months of new usage data before getting a new solar quote. Changing a few lights to LEDs saved 10%+ on our $600 annual bill.

  • Will Bloomfield February 8, 2018, 12:57 pm

    This news story today discusses how libertarian Congressman Tom Massie integrated a used Tesla car battery to power his off-the-grid home, which also uses solar panels.


  • Bakari Kafele February 8, 2018, 12:59 pm

    Hey, I just finished the last steps of my solar system last month!
    The city inspectors and staff, the utility company, the solar wholesalers, no one I talked to had ever heard of a homeowner doing an entire grid-tie install themselves!

    I found the permit and inspection process to be many many times more difficult and time consuming than the actual process of installing them. And, since I have a very small (5 panel) system, the fees were more than 50% as high as the actual cost of the equipment itself! So, that’s one important way that a larger system is more cost effective. Still, I managed to get 1.4kW system for just under $2000 ($3000 including permits and other government mandated costs), which just about exactly covers all the extra power used by charging our electric car, and should have a payback time of only a few years.

    One important thing for a budget minded DIYer to note: many states and utility companies have just adopted a new standard, so that many existing inverters, even ones only a year old, are now obsolete. Make sure, if you find a great deal on Ebay or locally or whatever, that the inverter (or set of microinverters) you are looking at meet your local utility company’s 2018 standards.
    Mine didn’t; fortunately I was able to get a waiver since I started my project before the new rules went into effect, but anyone buying now wouldn’t have that option.

    • Renard March 2, 2018, 6:53 am

      I feel your pain…..my wife is an architect and we are able to crank line drawings and the like quickly. Even so, it took 3+ months from initial review to final approval of our 6.875kW system. It only took a week to install our ground mount system. Same comments……’homeowner’s don’t do this’. It isn’t the difficulty of the install, it is the difficulty and obtuse nature of permitting that drove me nuts. Now in the payoff stage …. had a 102kW surplus for February. YAY!

  • Alexander February 8, 2018, 12:59 pm

    My brain started to hurt when I opened up that “one line diagram” example! Man that looks intense. Ive always wanted to do solar panels, just never have taken the time to see about DIY for it.

    I applaud you man for getting it done. If you are ever in Indianapolis, feel free to come on by and help me get started. :)

  • Peter Bryenton February 8, 2018, 1:18 pm

    Well presented, thank you.

    Most domestic homes here in the UK have thin-film solar PV panel systems installed as standard nowadays. Plenty of home owners are selling surplus electricity back to the power companies. The brand new community centre in the village where I live is “zero-carbon”.

  • Marcia February 8, 2018, 1:29 pm

    Pretty cool stuff. We’ve tossed around the idea of solar if we ever do work on our house (I’d really like a second bathroom and a tiny bit more space besides!) The math has never ever worked out, but at this $ amount, it would pay for itself in about 7 years (we use <$1000 of electricity a year).

    I have driven past huge solar farms in the CA desert, and they are impressive. I also had the pleasure of vacationing in Durango last July with my family, and it was a lovely little town! I enjoyed running along the river, and we found a great playground (maybe a LITTLE too close to the sewage treatment facility) for the kids to play on and have picnic dinners at.

  • Brian February 8, 2018, 1:31 pm

    I keep thinking of long-term costs.

    1) You mentioned putting several holes in your roof, and sealing them. Does that create long-term weakness in the roof? Will the roof need to be replaced sooner because of the modifications?

    2) What will you do when the roof needs work? Do you have to remove the panels?

    3) How long will the system last without intervention? Will it eventually need repairs, maintenance, or upgrades and replacement? Will these extra costs extend the payback period?

    • Bakari Kafele February 12, 2018, 10:27 am

      1) You install the bolts into the roof rafters, not just any random spot in the roof. Just like when you attach something to the wall and find the studs first. Finding the rafters is the hardest part of the install.
      You use sealant in the hole before screwing in the bolt, and install flashing between the roof and the bracket. If its done right, its just as reliable as any other roof penetration (like vents or skylights)

      2) yup. if the roof is more than 5-10 years old (depending on the type) you probably want to replace the roof before adding solar. Then, it 20 years or so, both need to be replaced at the same time anyway.

      3)Maintenance means washing the panels once a year or so. In CA we have 10 years to upgrade to UL-1741-SA standard inverters, which are better for the utility companies power management. Other states are likely to adopt the same standard soon. The system will continue producing power, but panels lose efficiency over time and produce less power. 20 years is considered the “life span”, even though they will technically produce some power much much longer. The pay back period – especially if you do the work yourself (labor is often 50% or more of the system cost) should be somewhere in the range of 2-10 years (depending on lots of factors), so you will almost always come out ahead.

  • Chris February 8, 2018, 2:00 pm

    Wicked cool project! I might try this on my new shed.

  • ultrarunner February 8, 2018, 2:31 pm

    Great write-up, thanks for taking the time!

    I’ve been house-hacking my way into enough rental properties to retire (getting closer!) so solar hasn’t made much sense, with the moving every year or so… (buy a house as owner-occupied, renovate it, live there the bank-required 12 months, buy another, move, rent first house out, repeat, retire) so I haven’t been paying very close attention to the prices. They’ve really come down a LOT!! I think the last time I seriously looked, it was between $8-9/watt.

    I helped a friend here in Boulder put an array on his house about 3 years ago. It was shockingly easy (pun intended) to install. Three of us did the entire system in one day.

    With the convergence of an EV + my “forever home” in the nearish future, I’ll start keeping a closer eye on things.

    Thanks again!

  • Stephen February 8, 2018, 3:15 pm

    Great article! I think I’ve emailed you two or three times asking about DIY solar after you mentioned it offhand in an article or on twitter or something.

    Question, in looking at the payback, the % return looks great when compared to traditional investments. That said, do you have any data on how it affects resale prices of homes? While the other benefits are nice, from a financial perspective it would suck to install these and then move in 2-3 years and not get any payback for them.

  • Scott Lunt February 8, 2018, 3:22 pm

    Thanks MMM and John – I’ve been waiting patiently for an article about DIY solar panels. I figured it was only a matter of time! I live in Denver with an open north-facing roof and garage perfect for solar. I have been planning my life around eventually having them (e.g. electric heating and plans for a future electric car) and figure I’d do that (DIY style) this year.

    Two questions:
    1 – how, pray tell, did you score 300W panels at $130/ea and how can I get in on that?? Where did you buy the brackets/inverter, etc?

    2 – How does the federal rebates apply for DIY projects like this? Do you simply submit all of your receipts when filing taxes??


    • Mr. Money Mustache February 10, 2018, 4:02 pm

      I’ll have to update you on the tax credit, but as far as I know you simply fill out the right IRS forms (or Turbotax boxes) to claim the refund. As with most deductible expenses and credits, you save the receipts in case you are audited, but don’t send them in.

      • Bakari Kafele February 12, 2018, 10:20 am

        The credits had expired for a month there, but the new budget ended up restoring it after all.
        MMM’s guess is right about how you claim it

  • Jason February 8, 2018, 3:45 pm

    Added bonus in Arizona: Our roof was old and leaky when we decided to get solar installed on our home. In order to safely install solar panels on your roof, the roof needs to be in good repair. So, in addition to the 30% tax credit we received for the solar system itself , we also got a 30% tax credit on all the roof repairs because they were necessary to install the solar. Cool :)

  • Sean February 8, 2018, 4:09 pm

    I have a strong belief the solar + battery system is in its infant stage of applications. For example, what of collapsible thin film chargers for long car/camping trips? High efficiency cells for car roofs/hoods? Everything from smartphone backs to bike lanes/sidewalks could use solar panels and fundamentally change accessibility and quality of life for so many people. When solar and batteries sees mass adoption there will be massive geopolitical shifts! What an exciting time to be alive; great article.

  • DAVID February 8, 2018, 5:04 pm

    Awesome stuff. We went solar in 2017 as well. Not DIY, but paid for. Total cost $5,500 USD for a 4.5kw system and power diverter(for heating hot water with excess power) installed, and permitted. This is all without any government incentives.

    I did some fuzzy maths to help my co-workers decide if going solar was worth it for them. Turns out some people could end up becoming $867,000 richer by going solar and putting the cost on their mortgage.


  • Ian February 8, 2018, 5:15 pm

    The article made me check out the viability of Solar in our area (Calgary, AB, Canada). In checking my energy bill, only 34% ($45/mo) of my bill was actually electricity and the other 66% of the electrical bill is fixed costs (administration, distribution, transmission,Balancing Pool Allocation, and rate rider). So unless I go off the grid with a battery system to remove those costs as well, the ROI is not looking good. If I spent ~$13,000 for a 6 kw system (with a 30% provincial rebate for the system), I could save only $540/year in actual electricity costs. Sadly, it’s hard to justify the up-front cash outlay.

    • Bakari Kafele February 12, 2018, 10:31 am

      Check with the utility company, they might not bill net energy metering the same way, or the fixed cost might get prorated.

  • Jamie February 8, 2018, 6:34 pm

    Great article as always.

    Our solar story should be interesting as it’s somewhat Mustachian. A friend of mine set up a non-profit solar advocacy group in our community. The sole aim was to encourage people to get solar, and given we’re in Australia it’s really a no-brainer. The kicker though was that he organised a bulk-buy with his installer. If he got the installer 25 confirmed installs the guy said he’d chop $1000 of the price. The bulk buy is now up to 67 installs with a few dozen yet to be installed!

    I love the Mustachianism of this approach – connect with your local installers, do a deal and benefit your local community, all while saving admin and marketing costs all round and making the whole process more efficient. The great thing too was that the advocacy group took a lot of the confusion out of the process and provided a level of trust for people. This was key. I even went and got it installed. Our system has been working brilliantly since September. My last electricity bill was $5 ex tax.

    As a side note I’m still amazed that solar isn’t a minimum building requirement here in Australia.

  • Greg February 8, 2018, 7:34 pm

    Five years ago we installed a solar array on our medical office building at a cost of $90,000 after incentives. We financed it, and have just paid the loan off at a total cost of about $100,000 when you include interest. Thus far, the panels have resulted in $35,000 paid to us by the utility company, or about $7000 per year. Unfortunately, our electric bill is around $30,000 per year, if you can believe that. We have a lot of computers and servers and other electrical equipment plus we live in a warm climate which requires air-conditioning, since our patients haven’t subscribed to the Mustachian philosophy when it comes to an expected temperature inside a doctor’s building. Long story short, it is going to take us about 15 years to recoup our investment. Probably not the best return given the opportunity cost of investing the same amount of money in the stock market over that period of time. Nonetheless, none of the partners are complaining as we all have a bit of an environmental soft spot. We don’t regret it as it’s really a drop in the bucket in comparison to all of the other overhead. I suppose if we were to undertake this project now it would be cheaper and more economically viable.

  • Marc Hastenteufel February 8, 2018, 9:23 pm

    Another great one!
    Thank you Mr. MM – hope this will inspire many!

  • Ted February 8, 2018, 9:28 pm

    Well done! We’re almost a year into our own 3.9 kW system. We get about 2/3 the energy that you do out of our slightly larger system here in rainy Portland, OR. By doing all the energy efficiency we could do first, we were able to turn our 1975 home into a net zero home with a system that’s smaller than average.

    Our net metering policies aren’t as profitable, but any extra credits we generate over the course of a year get donated to the program that helps low income customers pay their bills. Win-Win-Win.

  • Anonymous February 8, 2018, 10:02 pm

    > Unless you’re building an off-the-grid cabin, in almost all cases you will want to “grid-tie” your solar array, so you can effectively sell your surplus electricity back to the power company (and thus, other nearby customers), cleaning up your whole town and saving the huge cost of batteries.

    Sadly, in the area I’m in, while you can use the grid as a bottomless battery, the surplus gets stolen on an annual basis and reset to zero.

  • Steve Boyko February 8, 2018, 10:21 pm

    Was there a need for a transfer switch at the panel? Normally utilities do not want you injecting power into the grid during a power outage, to protect the workers trying to restore power. Is it built into the equipment you used?

    • Mr. Money Mustache February 10, 2018, 3:49 pm

      Yes, it’s built in. Solaredge inverters have automatic “anti-islanding” protection, where if the AC grid goes down, they stop producing power. Plus they shut down all the DC voltage as well, by communicating with the optimizers.

    • Bakari Kafele February 12, 2018, 10:32 am

      I think almost all (legal) grid-tie inverters have that built in, and many (most?) local code requires a shut-off switch in addition (one that the utility company can lock in the off position).
      I bought the disconnect switch on ebay for $35.

  • Bf February 9, 2018, 7:24 am

    Add metal mesh around the perimeter to keep out pigeons and other animals. They nested under my panels.

  • Emil February 9, 2018, 7:36 am

    Hi, longtime reader from Norway checking in.

    MMM, I seem to remember you did a previous post on metal roof panels. Take a look at this, see if you can Google translate it: http://www.namdalsavisa.no/artikkel/2018/01/26/Rune-%C3%B8nsker-%C3%A5-etterlate-minst-mulig-avtrykk-15974595.ece?rs96671

    My parents neighbor, just put an integrated solar panel roof om his garage. The solar panels replaces the metal roof = additional savings and maximized solar panel area. Cool stuff.

  • Renan February 9, 2018, 8:07 am

    I always wanted to go solar, but was avoiding because of the high prices here in Brazil (since most of that stuff is imported, cost depends on how many dollars worth the Brazilian currency, and the “Real” buys about 30 cents).

    Now I read your post and just check current prices. They gone amazingly down since the last time I checked.

    My house is located on southern, and have a roof that is perfectly pointed to North. Even in the winter we have sunny days.

    A couple years ago the state-owned eletric company decided to pay HALF the price if anyone wanted to install solar panels.

    I can’t understand why so few people has installed it.

    Great post! Please keep us informed about how things are going with your solar-powered HQ.

    Sorry for English mistakes in case I made some :P

  • Dana February 9, 2018, 8:25 am

    Thank you for writing this post! I remember seeing the video about Charles Shaw building that school out in Durango…I was SO inspired and I still am. I think that is so epic! I’m really lacking a good community of friends in my life right now and I envy people who find themselves living in a loving community of like minded friends.

  • Brent Eamer February 9, 2018, 10:14 am

    Greetings from Prince Edward Island. I have been dabbling in solar for twenty years now. Last summer I moved my panels to a true south location. 45 Degrees. I have 2.5kw, Two Blue sky MPPT’s and Outback FlexMax 80. Six Surettes, S600’s and an Outback VFX2812 Oddly enough this is a hobby , as I am still on grid. It’s more of a control thing for me. I want power in the event of a blackout. I also have an IOTA 90 charger that I can run off a generator (propane and gas) in the event of low light. As far as snow, as someone mentioned, a bit of exposed panels even on the coldest day will yield a clear panel in a few hours

  • Sherry Ellesson February 9, 2018, 10:36 am

    Mr MMM, I live on some open acreage and am considering building a sort of carport structure but without a solid roof – in other words, it would be like a gazebo but with the correct pitch, using the solar panels as a de facto “roof” (which would provide more UV protection and a bit of precip protection for my tractor, which has been out in the weather too long for its own good. I could have the corner of this structure about 10′ from where my electrical box is mounted on the outside of the house without encountering the underground lead in from the road. I’d appreciate any thoughts or cautions you might have. Thanks for such an encouraging article – living alone on a retirement income means DIY are my middle initials!

  • Josh Perrin February 9, 2018, 1:36 pm

    Hey MMM, love the blog, and love this writeup, i’m looking to buy land, and build a home in the next few years. I’m located in NS, Canada, and solar is going to be one of my must have projects for my new build. But i’m curious what do you do for heat, and curious on your opinion for heating options? I’m still weighing different heating options, and wondering if it’s advisable to try and heat with solar electricity (heat pump), or to use a different sort of heating solution. Thanks!

    • Mr. Money Mustache February 10, 2018, 3:38 pm

      If you have enough surplus electricity (i.e. lots of room and get your solar stuff at a good price), a heat pump is usually the best option. Definitely the most eco-friendly, and depending on natural gas prices in your area probably the cheapest too.

      Within a decade or two, fossil fuel heat will be something people are ripping out of their houses to replace with heat pumps, so it might be worth thinking ahead to that as well.

      Also, look at the Passive House ideas for really good insulation and design. This will make it so heat is only a small consideration anyway.

  • Michael February 9, 2018, 6:52 pm

    Solar power at the government level and also electric cars are all the rage over in China …. it is easier to get a licence plate for electric cars and they put in a plug-in for your apartment building parking spots … in the big cities – where new car licence plates are limited by lottery.

  • Finn Peacock February 9, 2018, 7:29 pm

    MMM, I’m in Australia – so this is fascinating.

    The way you have calculated your solar savings implies a 1:1 feed-in-rate? i.e. you earn the same for exporting a kWh as you pay for importing a kWh from the grid?

    If that is true then that is an incredible investment at an installed cost of ~$1 / Watt.

    In Australia we pay about US$0.25 for a kWh from the grid, and get a third to half of that when we sell a kWh to the grid.

    This means us Aussie PV owners try really hard to use our electricity during the day, and why Australia is one of Tesla’s biggest markets for the Powerwall (although interestingly even with those rates a Powerwall 2 cannot pay for itself before the warranty has expired).

    Also in Australia we have the cheapest PV in the world. You can get good quality PV professionally installed, for about US$1 per watt. About 23% of houses have it.

  • Fiorintinaturna February 10, 2018, 5:31 am

    I have been reading from the start of the archives and i am now “up to date”

    Sad times!

  • Stop Ironing Shirts February 10, 2018, 5:40 am

    I’m going to ask this as the non-electrical engineer.

    How difficult was (and how expensive) was the part you change out in your power meter or main power box? I imagine part of the cost comes from having a variable power input from solar then pulling the difference your house needs off the grid? Designing future houses/power boxes seems to be the main thing that would hold back the portable solar unit idea. I have some perfect southern facing roofs, but not being able to throw panels up there and just run one cord into the box like the 220 outlet you referenced is what’s holding me back.

    I’d love to do it, but am not going to be in my current location long enough to make this anywhere close to economical.

    • Bakari Kafele February 12, 2018, 10:39 am

      You don’t change the meter, if it needs to be changed the utility company does it. If you already have a digital meter, it probably doesn’t need to be changed.

      The attachment point in the main power box is just a regular 220v double circuit breaker. You buy it at any hardware store, shut off the main power, and snap it into place. Connect 2 wires. That’s it. You have to have two open slots in your breaker box for the new double breaker to go.

      If you use microinverters, it pretty much is all plug and play: plug panels into inverters, inverters into main connecting cable, cable runs through a shut-off switch into the new breaker you just installed. For a central inverter like MMMs system, you add like 2 steps. Still not as complex as it seems like it would be.

      I felt the same way before I did mine, but it was actually very straight forward

    • Thriftychemist February 12, 2018, 10:40 am

      When I had solar installed in Utah, the power company installed the net meter after all of the rest was in place and approved by their inspector. I didn’t have to pay anything extra for that meter. The net meter just records power in and out, there isn’t any need to “decide” whether the power goes in or out. It’s just a matter of use and production. If you use more than you produce, you’ll pull power from the grid. If you produce more than you use, it goes back. Our digital meter records power that flows each way, not just the net flow.

      In our system, the inverter connects directly to the meter, so no changes were required to the service entering the home. If we choose to go off-grid in the future (not likely) we would have to disconnect the inverter from the meter and the main from the meter into the house. We’d then put in a battery system, connect the inverter to the battery, and the service from the battery to the electrical panel. It would be more work, but even so the actual panel itself wouldn’t have to be redesigned as long as the battery system provided enough power.

  • mrpriceisright February 10, 2018, 8:36 am

    Really enjoyed the article, most informative and particularly the diy aspects. About to start building a home on 8 acres near camp Pendleton, ca. Have been looking at solar, even more so since the electric co came out and said it would probably cost $50k to get power to the house (even though we have already have a power pole/drop/panel on the property 400 ft away. My immediate thought was that a full off grid system with a power wall or two, would probably be significantly cheaper than that and would then cost zero for energy needs. The Tesla roof looks interesting but is no where close to being available, is super expensive and probably wouldn’t do well on our roof, which has lots of hips and angles. There will be a large area next to the house for leach field use and thinking about a free standing solar farm on that (also since it has limited other use). Anyone know of any restrictions on installing panels over a leach field? By the way, our direct neighbour (a large avocado farm in the hundreds of acres) has the biggest solar farm I’ve ever seen (about 2-3 acres of panels!) pumping well water is their biggest expense so it makes sense. They had to sue the utility to get them to buy the excess power and they subsequently put in a substation nearby to handle the power to the grid! . Keep the articles coming.

  • Michael B February 10, 2018, 9:27 am

    Hi MMM! I’m a student at the Northern Alberta Institute of Technology in Edmonton, Alberta, studying alternative energy technologies. I’m currently two months into my course on solar PV, and I have yet to hear of the “optimizers” you mention in this article. Modules today all come equipped with built-in diodes to help mitigate power losses from shading. I was wondering if you knew what specifically the optimizers do, or perhaps how they work?


    • Mr. Money Mustache February 10, 2018, 3:27 pm

      Hey Mike, they are effectively really smart DC-to-DC voltage converters. More info here: https://www.solaredge.com/us/products/power-optimizer#/

      • nice joy February 10, 2018, 4:37 pm

        Why cant they make it one piece? panel and optimizer in one piece. Also, is it possible to make stand alone solar system for charging electric cars or just the run the Ac unit.

        • Bakari Kafele February 12, 2018, 10:46 am

          They don’t make it one piece because not everyone uses them. The same panels can be used with a independent, battery backed 12V system, with micro-inverters, or with a central inverter with no optomizers (which are less needed if the spot faces the ideal angle and is never shaded at any point of the day). Having the system be as modulaized as possible keeps it less expensive.
          plus, all the brands use the same connectors, so you can mix and match to get better prices.

          It is possible to make a stand alone system, but you would likely use an entirely different set-up and different equipment. It would be inefficient to have an inverter take the 12-24V DC output of the panels, invert it to 220V AC, and then convert it back to DC to charge a battery (although I have no idea if a direct DC converter for electric cars actually exists!)

          A/C is one of the biggest power draws in a normal household, with an especially high surge power useage, so you would need a disproportionately big solar system (or a battery bank) to run AC without it being on the grid to handle the start-up demand.

  • Florida Mike February 10, 2018, 9:55 am

    Very cool writeup! Its been a project I have been thinking about for a while so this may convince me to take the next step. One question for anyone who knows the details of all this…. Is there any way to protect the panels from hail? Where I live gets a decent amount of hail each year and I am guessing a direct hit from even pea sized hail could be catastrophic.

    Any ideas?

    • David Classen February 11, 2018, 12:34 pm

      Ditto in north Texas and homeowners insurance only reimburses 50% of replacement costs.

    • Bakari Kafele February 12, 2018, 10:50 am

      They are pretty strong. The manufactures know hail exists, and they have warranties (typically 10-25 years)
      For example, I got the cheapest panels I could find, and the warranty covers hail up to 25mm at 80km/h (1 inch in diameter, traveling 50 mph)

  • EV February 10, 2018, 12:36 pm

    I first got the EV, and then the solar panels a few months after that. There seems to be a high correlation between EV users and solar panel installations. We have been Net 0 on our house for over a year now in southern california and it was one of the better decisions. Our break even on a large 10.5 kW system is about 5 years even at around $3.00/watt. After you figure in the 30% fed tax deduction, fuel savings from gasoline for EV the price goes down dramatically. Also, I paid on 4 new credit cards that offered 100k free points each, and cashed out about 2k in cash back (then closed cards). After the 5 years of “pre-paying” our electricity, we will have free power for the remaining 15-20 year life span of the panels. Panels do degrade, but it will still be worthwhile.

    After more than a full year running all on solar panels, we generate about $1,000 excess power per year which we do not really get credit for. This is after electric car charging, landscape lights, etc. So, our system might be a little oversized, but I’m fine with that. Mr MMM might not approve, but I am now mining a few graphics cards with the excess power for a passive income of about $20/day in alt coin currencies as a hobby.

  • nice joy February 10, 2018, 1:57 pm

    Worth reading this article https://www.cashcowcouple.com/save-money-solar-power-installation/
    This shows how to design and get the part list and buy those parts from another seller from much lower price

  • nice joy February 10, 2018, 2:29 pm


    free designing tool for your solar project. Also get the part list.

  • nice joy February 10, 2018, 2:31 pm

    After getting the parts list order the parts from https://www.solaris-shop.com/ for much lower price

  • nice joy February 10, 2018, 2:38 pm

    Wondering why you did not use micro inverter

  • fahad syed February 10, 2018, 2:47 pm

    So, our current government has decided to levy tariffs on imported chinese solar panels. Is this going to drastically increase the cost of installing a solar panel and generating solar energy?

  • nice joy February 10, 2018, 4:34 pm

    Hi MMM how can I get the panels for 130 ?

  • Michael R February 10, 2018, 7:30 pm

    MMM – did I miss the description of ongoing maintenance?

    MMM & All of you who’ve done this – what are the long term maintenance activities for an installed system? Andrew Miller mentioned squirrel damage repair. That is hopefully a semi-rare event.

    I noted the system is installed in series. If one component dies the system will go offline. Why was that wiring option used?

    This great article is bookmarked for reference when we move in a couple of years and will be in a house we’re staying with.
    Thanks much.

    • Thriftychemist February 12, 2018, 10:44 am

      For our system the maintenance is nil. Rain and snow wash even our stubborn clay dust off our panels. If I had to, I could get up and wash them with a soapy brush, but there has been no need to do so over the year and a bit I’ve had them. Eventually, the performance of the panels will degrade, but replacing the panels themselves isn’t all that much work. Similarly, if the inverter fails, it’s not that much work to disconnect and replace it.

    • Bakari Kafele February 12, 2018, 10:56 am

      The normal expected maintenance is to wash the panels once a year. Maybe more or less depending on local conditions. Panels lose about 20% of rated power in 20 years, so that is their official lifespan. You could keep them much longer if you are ok with them producing less.
      They are actually not in series, they just look like it. Everything plugs into a single cable with its own attachments along the run. If any one goes down, the others still produce. Of course, if something breaks the wires themselves, nothing before the break would work, but thats the same with all electric wires.
      Also, there are rarely failures, since there are no moving parts.


Leave a Reply

To keep things non-promotional, please use a real name or nickname
(not Blogger @ My Blog Name)

The most useful comments are those written with the goal of learning from or helping out other readers – after reading the whole article and all the earlier comments. Complaints and insults generally won’t make the cut here, but by all means write them on your own blog!


welcome new readers

Take a look around. If you think you are hardcore enough to handle Maximum Mustache, feel free to start at the first article and read your way up to the present using the links at the bottom of each article.

For more casual sampling, have a look at this complete list of all posts since the beginning of time or download the mobile app. Go ahead and click on any titles that intrigue you, and I hope to see you around here more often.

Love, Mr. Money Mustache

latest tweets