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Years to breakeven..? PA Solar worth it?


Active Member
Dec 5, 2014
Trying to do some math, and thinking out-loud; I've run the numbers a few times, and haven't yet found solar to be financially advantageous in PA.

Tesla says I need a 16.32 kW system. $33,000 (plus 9k rebates).

Over the last 3 years I average: 2,400 kWh/month. (No anticipated changes coming up). (Would love a hot tub).

Here in PA, zip 17339, we have fairly cheap power.
ALL IN (not just generation) over the last 3 years: $0.1025 / kWh

I switch generation companies religiously to get the cheapest power.

Anyway, in my zip code with not ideal sunshine and cheap power... is the payback really 10 years?

Price After Incentives $23,185.

Google says: 1,445 hours of usable sunlight per year x 16.32 = 23,582.4 kWh/year. 1,965/month.
After Solar: 435 kWh/month from grid/average.

1965 / 2400 kWh = 80% solar powered house.

Grid Power: $2,952 / year
Solar Offset: $2,361.6 / year

$23,185 / $2,361 = about 10 years

Of course this doesn't account for missed opportunity costs of the $23($32) upfront costs.
I can do better than their 5% loan if I wanted to as well.

So after 10 years, when the panels are "paid for by the reduced electric bill", I just have a super cheap electric bill for life then, at the property.

Am I missing anything? 10 years seems reasonable for ROI for something for the house. Although it's a long time...

At 10 years, saving $2,361/year starts, so 10 years of that is $23,610. 20 year panels.


Supporting Member
Jul 21, 2012
SF Bay Area
One of the ways I like looking at this is to calculate my per kWh cost with solar over whatever period I deemed as its lifetime (include cost of money, maintenance). You can think of solar as just prepaying for a bucket (with some uncertainty) of electrons. Rough numbers say solar is below $0.10/kWh. Given your low energy costs, 10 years to break even is not surprising. If you are modeling opportunity costs then you should also be modeling how energy prices are likely to change.


Nov 7, 2018
Northern NJ
My electricity costs are twice yours, and I get SRECs which halves the payback period, and I calculate about 3.5 years payback with a slightly smaller system, so your calculations seem quite accurate to me.

I would add that the Tesla estimates are typically conservative and you may want to check PVWatts for more accurate yearly production.


Dec 13, 2020
Are you likely to stay in the house for those 10 years? If so then I would look at is from a finance point of view. There are very few places where you can put your money and earn 10% tax free every year (which is essentially what you are getting).


Nov 2, 2017
Berkeley, CA
Don't forget the personal utility of avoiding the unpriced externalities caused by using grid power. The utility (as in utility function) payback time should be less than the dollar payback time.

Cheers, Wayne


Well-Known Member
Feb 28, 2015
Merced, CA
8.16 KW + 3 Powerwalls. I'm PG&E on EV-2A. My ROI payback is 6.8 years assuming I don't have any weeks long inverter failures in the middle of the summer. The interesting thing is that adding the powerwalls didn't increase the payback time hardly at due to the offset of eliminating 100% peak usage.


Feb 5, 2021
New Jersey
My numbers are as under:

Historical Usage: 14800 kWh / year
Installed Capacity: 14.28 kW
Cost to install: $21,500 after rebate
Cost of funds: 3.5% (HELOC) hopefully stays around here
Cost of Electricity: 13.5c net
TREC: $1470 / year (hoping I generate 16 mW)

With these numbers I calculated years to payback at around 6-7 years. I will never put HELOC in any earnings investment as I want to keep my home.

I think with these numbers my ROI is 16% and cost of funds is 3.5% so net 12.5% (tax free)

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