Solar Loan Calculator
Calculate your monthly payment, total interest, and whether your solar savings exceed your loan payment from day one.
| Year | Payment | Interest | Savings | Balance |
|---|---|---|---|---|
| Year 1 | $2,220 | $1,227 | $1,650 | $17,007 |
| Year 2 | $2,220 | $1,155 | $1,650 | $15,942 |
| Year 3 | $2,220 | $1,078 | $1,650 | $14,800 |
| Year 4 | $2,220 | $996 | $1,650 | $13,575 |
| Year 5 | $2,220 | $907 | $1,650 | $12,262 |
| Year 6 | $2,220 | $813 | $1,650 | $10,855 |
| Year 7 | $2,220 | $711 | $1,650 | $9,346 |
| Year 8 | $2,220 | $602 | $1,650 | $7,728 |
| Year 9 | $2,220 | $485 | $1,650 | $5,993 |
| Year 10 | $2,220 | $360 | $1,650 | $4,133 |
| Year 11 | $2,220 | $226 | $1,650 | $2,138 |
| Year 12 | $2,220 | $82 | $1,650 | Paid off |
How to Use This Calculator
Enter your loan details
Enter the loan amount — this is the system cost after any down payment. If you're applying the 30% federal tax credit to reduce your principal (common with Goodleap and Mosaic loans), enter the post-credit amount. The interest rate depends on your credit score and lender. Solar-specific loans in 2026 typically range from 4.99% (excellent credit) to 9.99% (fair credit).
Set the term and electricity rate
Common solar loan terms are 10, 12, 15, and 20 years. Shorter terms mean higher monthly payments but significantly less total interest. Enter your current electricity rate to calculate the monthly savings from your solar production — this is what offsets your loan payment. The "net monthly cost" shows whether your savings exceed your payment (cash-flow positive) or not.
Read the effective cost
The effective cost is the total financial cost of the system after subtracting electricity savings during the loan period. If the effective cost is negative, your solar savings during the loan term exceed the total amount you paid (principal + interest) — meaning the system has already paid for itself before you even own it free and clear.
The Formula
The standard amortization formula ensures equal monthly payments throughout the loan term. Early payments are mostly interest; later payments are mostly principal. The interest is tax-deductible if you use a home equity loan or HELOC for solar — check with your tax advisor. Solar-specific loans (unsecured) are typically not tax-deductible.
Example
Jordan — 8kW system financed with a solar loan
Jordan installs an 8kW system for $22,000 gross. After the 30% ITC ($6,600), they finance $15,400 at 6.99% over 12 years. The system produces 11,000 kWh/year and Jordan pays $0.16/kWh.
Result
Jordan pays $23/month more than they save during the loan period — barely noticeable. After 12 years, they own the system outright with no payment. The effective cost after 12 years of savings is only $3,260 — essentially getting a 22kW solar system for a fraction of its cost. After payoff, the $147/month savings are pure benefit for 13+ more years.