Solar Loan Calculator
See the monthly payment, total interest, and total cost of financing a solar system, so you can compare a loan against paying cash.
What your result means
Monthly payment is your fixed solar loan installment. Total interest is the extra you pay over the life of the loan, and total of payments is principal plus interest. Compare the monthly payment against the electricity savings from our solar panel cost calculator — if savings beat the payment, the loan is cashflow-positive.
How to use this calculator
- Enter the amount you'll finance (often the net cost after the 30% credit).
- Enter the loan's APR.
- Enter the term in years (10, 15, 20, or 25 are common).
- Read your monthly payment, total interest, and total of payments.
- Compare the monthly payment to your expected electricity savings.
The formula
This is the standard amortized loan formula. A longer term lowers the monthly payment but raises total interest; a shorter term costs less overall but more per month.
Worked example
Financing $16,800 (an 8 kW system's net cost) at 6.5% over 15 years works out to about $146 a month. Over the full term you'd pay roughly $9,500 in interest, for about $26,300 total. If solar trims $150 a month off your bill, the loan is cashflow-positive.
How term changes a $16,800 solar loan at 6.5%
| Term | Monthly payment | Total interest |
|---|---|---|
| 10 years | ~$191 | ~$6,100 |
| 15 years | ~$146 | ~$9,500 |
| 20 years | ~$125 | ~$13,300 |
| 25 years | ~$113 | ~$17,300 |
| Cash | — | $0 |
Tips & gotchas
- Aim for a payment at or below your electricity savings — then solar pays for itself monthly.
- Watch for solar loan "dealer fees" baked into the rate; a lower advertised APR can hide them.
- Apply the tax credit to the principal (a re-amortization) if your loan allows it.
- Shorter terms cost far less interest; take the shortest payment you can comfortably afford.
- Compare a solar loan against a HELOC — sometimes home equity is cheaper.
Frequently asked questions
What's the monthly payment on a solar loan?
For a $16,800 loan at 6.5% over 15 years, about $146 a month. Payment depends on the amount financed, the APR, and the term.
Should I finance solar or pay cash?
Cash avoids interest and pays back fastest in pure terms; a loan can be cashflow-positive from day one if the payment is below your electricity savings. Compare both.
Do solar loans have hidden fees?
Some do. A very low advertised APR can carry a large "dealer fee" rolled into the financed amount. Always compare the total of payments, not just the rate.
What loan term is best for solar?
Shorter terms cost much less interest but more per month. Many homeowners pick 15 years as a balance; choose the shortest payment you can comfortably cover.
Can I use the tax credit to pay down the loan?
Often yes. Many solar loans expect you to apply the 30% credit to principal within 12-18 months, which keeps the payment low. Confirm your loan's terms.
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Estimates only — see our full disclaimer.