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Solar Panel Payback

solar House made with moneyHere is a compelling calculation for those of you that are contemplating the purchase of solar panels.

We purchased our 3.6KW solar panels almost 4 years ago for a net cost of $22,500 after tax incentives. In the 4 years, we’ve saved an average of $90 per month on normal electricity usage.
That’s $1080/year savings. At that rate, we would have the panels paid off in 20 years. Commuting daily for about 50 miles in my electric car, we are saving an additional $120 per month on gas, that’s an added ~$1400/year savings. Including the gas savings from the car, the panel payoff accelerates to 9 years. I am now tracking the actual payback of the solar panels here:

Solar Payoff Progress

I am contemplating the sale of my 2009 Corolla S and purchasing an all electric Nissan Leaf for my wife. Assume she commutes for the same distance daily, our payoff should accelerate to 5 years.


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Posted in MR2EV, solar panels

2 Responses to “Solar Panel Payback”

  • Levi says:

    I read your latest blog posting. Does your solar system produce enough extra power to charge two cars? Also, you said you were saving $90 per month on electric bill, is that how much you used to pay before you had the panels? Doesn’t PG&E pay you for the extra power you generate and feed into the grid?

    • Ken says:

      My solar panels will come close to cover charging 2 cars. Even it if doesn’t, The cost of electricity is $0.12/kwh, which will is good for 3 miles or so. Assume 50 miles daily commute, the extra cost per day is $2. The car will replace a Camry which, assume 25mi/gallon, will use 2 gallons of gas per day. At $3.85/gallon, the cost of gas will be $7.70/day. That’s more than $5/day savings or $107/month.

      The $90/month is the estimated cost of the electricity that we have used on a monthly basis (via monthly meter reads multiplied by the cost of the power) up till now. Adding the car will likely be a little more due to charging the car.

      PG and E does pay us for extra power at the end of the year, but it is not significant. They pay us $0.07/kwh at the end of the year. I’d rather use it than get paid at the low rate. :)

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