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  • Keith Groninger

Solar Panel Math

Updated: Feb 18

I’ve done this before but it’s worth sharing again.

We are installing 12 solar panels on a new home soon, so I thought I’d run the numbers again.

12) 290 wall solar panels - $10,000 installed.

30% federal tax credit - <$3,000>

Net investment cost - $7,000

12 x 290 watts per panel = 3480 watts

8 hours sunlight per day average rule of thumb

30 days per month

3480 x 8 x 30 = 835,200 watt hours per month

Or 835 kilowatts saved per month (divide by 1000 to convert to kilowatts)

Winter Park Utilities charges about $0.12 per kwh (kilowatt hour)

OUC charges about $0.11 per kwh

I checked my current and previous utility bills.

834 kilowatts x .11 = $92 savings per month

$92 x 12 months = $1104 per year

Divided by $7,000 investment equals a 15.7% annual return.

Keep in mind that this is actual cost savings or a tax free return.



If you wonder how long solar panels take to pay for themselves, it’s 6.3 years. Then it’s free power.

Or if you look at it from a monthly expense. At today’s interest rates, the $7,000 investment would add about $32 a month to your mortgage payment. So since the solar panels save $92, you’d be wasting $60 per month if you don’t put solar panels on your house.

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