patrick.net

don’t have them. but friend installed panels, we did work together wasn’t bad at all, saved a lot of money. just paid 500 for design. because of very low cost of self install with friends help he is saving money according to him after 4 years.

he isn’t disconnected, no battery, just panels pushing to grid. some cheap chinese panels.

hope this helps.

Eman says

Cost is $17.4K after tax incentives. It would cover my monthly electricity bill of $230/mo on average. Add in a powerwall will increase the cost by $8k. Without the powerwall, it’s about 15% ROI. What am I missing?

ROI works if your capital remains intact. That is, if you put that $17.4k in the bank and got $230/mo, that would be 15% ROI. In the case of solar panels, that $17.4k is a sunk cost and you must include a payback period to calculate a return. You are 6 years before you make a dime, and that is if the solar panels wipe out your entire electric bill for that time.

How did you calculate it?

I think the right way to model a decision like this is to make sure you account for cost of capital, and the calculations should use compound interest math, including expectations of future electric prices. I usually code my own calculators (which I wont share, as it would disclose my identity), but here's a calc that's on the web and can be shoehorned into working decently for this type of solar calculation.

solar cost = 24K + tax - 6600k rebate = about $19k capital outlay
monthly savings is usually your current bill minus about $10 minimum fee = $220

The idea is to model 2 scenarios:

#1 no solar, no $19k solar capital outlay, you will still pay $220 electric bill every month (w/ a 3% / yr bill increase), but you buy 19k of stocks or some other investment that will grant 7% CAGR (or whatever rate you feel is realistic).
#2 you buy solar instead of stocks, no more electric bill.

1 https://financialmentor.com/calculator/compound-interest-calculator?principal=100000&annualInterest=7&compoundingInterval=360&growType=2&yearsToGrow=20&additionFrequency=30&additionalAmount=-220&increaseContributionsBy=3&annualInflationRate=0&compute=1&source=patrick.net

2 https://financialmentor.com/calculator/compound-interest-calculator?principal=81000&annualInterest=7&compoundingInterval=360&growType=2&yearsToGrow=20&additionFrequency=30&additionalAmount=0&increaseContributionsBy=3&annualInflationRate=0&compute=1&source=patrick.net

The trick is to enter a sufficiently large starting account balance number to avoid going negative during the sim due to 20yrs of monthly electric bills. It doesnt matter what number you choose is, as long as you use the same figure for both calculations minus the 19k in #2. I used 100k and 81k. The reason the number doesnt matter is because we compare the ending figures to arrive at our desired final figure, which tells you how much better scenario 1 was vs 2.

I used 20 years since that's a typical solar system lifespan. I also set inflation to 0% because we account for inflation via the "Increase yearly contributions by" field, and assume the 7% CAGR for stocks is already inflation adjusted. So using the "average annual inflation rate" field would double adjust.

in 20 yrs, scenario #1 leaves you with $245,609 and #2 leaves you with $313,444

313,444 - 245,609 = $67,835

So in this case, scenario 2 was better by 67k, meaning solar offered gains above and beyond stocks by a good margin. It worked out to about 13% CAGR. Of course everyone needs to enter their own variables though.

Breakeven, where solar overtook stocks, occurred at about yr 9.

btw, https://projectsolar.io/?source=patrick.net has really good prices, both for a self install kit and full service install. Not sure of quality, but parts wise they use black mono panels and enphase micro inverters, which is considered good stuff generally. I plan to use them for a small system maybe this year.

Hircus says

btw, https://projectsolar.io/?source=patrick.net has really good prices, both for a self install kit and full service install. Not sure of quality, but parts wise they use black mono panels and enphase micro inverters, which is considered good stuff generally. I plan to use them for a small system maybe this year.

Thanks for sharing Hirus. You’re getting too fancy with the calculations, but I get the point. You’re likely an engineer with the way you analyze things. 9 years to break even is good enough. About 11% ROI.

Solar panels are ugly on a home. I am going to research it more when we go to build, but likely won't pull the trigger due to hail storms here. It would be built into the final home loan, so it would be the best time to do it, but my insurance rates go up because of the panels. Or I risk not insuring them. If I insure then I still have a minor monthly cost. But this is the forever home, so it might be worth it. We'll see.

If the build happens I'll probably start a thread for it and talk about all sorts of shit. Solar, pool, low voltage wiring for speakers and whole home shit, etc. I've been involved in a lot of builds, but this one is my baby and I'm not going to fuck around. No expense spared and I want to plan for future stuff. Gas lines, electric, internet and speaker cable run everywhere inside and out. Natural gas backup. Radiant heat in garage so I don't have a noisy heater and driveway so I don't have to shovel during winter. Hard wired cameras. Might do sprinkler system with a connection I have (inside) and also outside. My dog will likely pass soon, but still may put in an electric fence for a dog while excavating for the foundation. Lots to think of.

I've been using a small solar panel to maintain a questionable vehicle battery for several years now. This vehicle is rarely used and parked outdoors. Solar panel wasn't even installed until the battery was already almost bad.

I wanted to have solar panels installed in my last home in Las Vegas. The house was about 6000 square feet and being in Vegas I figured it would be ideal to have solar. Well, the house was too big for the special discounts that they offer so I would have had to spend way too much money up front to get eventual savings down the line and then, if I kept the house, the panels would have to be replaced, so I said, eff it and just made sure the house was as insulated as possible and we did triple glazing in all the windows and doors. Because I had the place done with 8 zones for the air and heating, it wasn't too bad to air condition in the summer. It was much cheaper than my house in Palm Springs which was a bit smaller. Putting in lots of different A/C zones allowed me to close off parts of the house when not in use (guest suites) and just cool the places I use most often. I have friends who installed solar in Vegas and who love the fact that their energy bills are super low.