Solar Loan Financing Calculator

What Is a Solar Loan? The Basics

A solar loan is money borrowed specifically to pay for a solar panel installation, repaid in fixed monthly installments over an agreed term — typically 5 to 25 years. Unlike a lease or power purchase agreement (PPA), a loan means you own the solar system from day one. You're simply spreading the cost over time instead of paying it all upfront.

Solar loans work like most other installment loans: a lender pays the installer (or reimburses you) for the system cost, and you repay the lender in monthly payments that include both principal and interest. Many solar-specific loans are structured around the expectation that you'll apply your federal tax credit refund to the balance in the first year, which is factored into the advertised rate and payment.

Homeowners use financing instead of paying cash for a simple reason: it lets them start saving on electricity immediately without depleting savings or investments to cover a $15,000–$35,000 upfront cost. The trade-off is interest — a loan will always cost more in total than paying cash, but for most households the monthly savings from solar production largely offset the loan payment.

How This Calculator Works Inputs & Outputs

The calculator above uses the standard loan amortization formula lenders use to generate a payment schedule. Here's what each input controls:

• Loan amount — your system cost minus any down payment. This is the principal you're borrowing.
• Down payment — money paid upfront that reduces the loan amount and, in turn, your monthly payment and total interest.
• Interest rate (APR) — the annual percentage rate charged on the outstanding balance, which determines how much of each payment goes to interest versus principal.
• Loan term — how many years you have to repay. Longer terms lower the monthly payment but increase total interest paid.
• Extra monthly payment — any amount you choose to pay above the required payment, applied directly to principal, which shortens your payoff time and reduces total interest.

And here's what you get back:

• Monthly payment — your required payment based on the standard amortization formula: M = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1], where P is the loan amount, r is the monthly interest rate, and n is the number of payments.
• Total interest — the sum of all interest paid over the life of the loan, accounting for any extra payments you've entered.
• Total cost — the loan amount plus total interest, i.e. everything you'll pay the lender.
• Payoff schedule — a year-by-year breakdown of how much of each year's payments goes to principal versus interest, and your remaining balance.

Types of Solar Loans Compare Options

Factors That Affect Solar Loan Payments What Moves the Numbers

• Loan amount. A larger loan means a larger monthly payment and more total interest, all else equal.
• Interest rate. Even a 1–2 point difference in APR can change total interest paid by thousands of dollars over a 15–20 year term.
• Credit score. Lenders price risk into your rate — stronger credit typically unlocks meaningfully lower APRs.
• Loan duration. Shorter terms mean higher monthly payments but far less interest paid overall; longer terms lower the payment but cost more in total.
• Down payment. Putting money down reduces the loan principal, which lowers both your payment and total interest.
• Dealer fees. Some solar loans bake an upfront "dealer fee" into the loan balance in exchange for a lower advertised rate — this raises your starting principal above the cash price of the system.
• Closing costs. Secured loans (like home equity products) can carry origination or closing fees that add to your total cost.

Example Loan Calculation Walk-Through

In this example, financing $20,000 at 6.5% APR over 15 years costs about $174 a month. Over the life of the loan, roughly $11,360 goes to interest — meaning the system ultimately costs about $31,360 including the $4,000 down payment, versus $24,000 if paid in cash. Many homeowners in this situation see monthly electricity savings that cover most or all of that $174 payment, effectively "trading" a utility bill for a loan payment while building toward owning their system outright.

Solar Loan vs Cash Purchase Side by Side

Pros & Cons of Solar Financing Weigh It Up

Tips to Reduce Loan Costs Save Money

1. Improve your credit score before applying. Paying down other debt and correcting any credit report errors ahead of time can meaningfully lower the rate you're offered.
2. Compare multiple lenders. Rates and fees vary significantly between solar-specific lenders, credit unions, and banks — a few quotes can save thousands over the loan term.
3. Make a larger down payment. Every dollar you put down reduces the principal you're paying interest on for the life of the loan.
4. Choose the shortest term you can comfortably afford. A shorter term means a higher monthly payment but substantially less total interest.
5. Consider extra principal payments. Even small additional payments applied to principal — as modeled in the calculator above — can shave years off your loan and save significant interest.

Frequently Asked Questions FAQ