Solar Loan Calculator
Calculate monthly solar loan payments, true APR with dealer fees, payback period, and 25-year savings vs. cash, lease, and PPA. Free, no signup.
Solar Loan Payment Calculator
Enter system cost, loan terms, and incentives. Get monthly payment, total interest paid, effective system cost, and 25-year savings comparison vs. cash purchase.
Fill in system cost and loan terms to see your monthly payment and 25-year savings.
| Solar Loan | Cash Purchase | Lease | PPA | |
|---|---|---|---|---|
| Enter details in the Loan Calculator tab to populate the comparison. | ||||
Lease / PPA Details (for comparison)
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What This Tool Covers
This solar loan calculator computes monthly loan payments, total interest paid, and effective system cost after incentives for financed solar installations. Compare loan financing against a cash purchase to find the break-even point and 25-year savings difference.
Inputs Required
- • Total system cost ($)
- • Down payment ($ or %)
- • Loan term (years)
- • Annual interest rate (%)
- • Federal ITC percentage
- • State incentives ($)
- • Annual energy savings ($)
Outputs Provided
- • Monthly loan payment ($)
- • Total interest paid over loan term
- • Effective system cost after incentives
- • Break-even vs. cash purchase (years)
- • 25-year net savings (loan vs. cash)
- • Monthly net cash flow (savings minus payment)
- • Loan amortization summary
Features
Monthly Cash Flow Positive Check
Shows whether the loan payment is covered by the monthly energy savings - a key selling point for zero-down solar financing when the customer is immediately cash flow positive.
Cash vs. Loan Comparison
Calculates the 25-year net savings difference between paying cash and financing, including the opportunity cost of the down payment and interest expense.
ITC Timing Modeling
Models the ITC as a Year 1 or Year 2 lump sum payment against loan principal - matching how solar loans with ITC paydown features actually work in practice.
How It Works
Enter System Cost and Down Payment
Input the total installed system cost and any down payment. Many solar loans are zero-down - leave the down payment at $0 to model a fully financed system.
Set Loan Terms
Enter the loan term in years (common options: 10, 12, 15, 20, or 25 years) and the annual interest rate from your financing partner or bank quote.
Add Incentives and Annual Savings
Enter the ITC percentage, any state credits or rebates, and the estimated annual energy savings in dollars. The tool applies incentives to reduce the effective loan principal.
Review Payment and Savings Summary
Get your monthly payment, total interest paid, monthly net cash flow (savings minus payment), and a 25-year comparison of the loan path versus paying cash upfront.
Compare Financing Scenarios
Run multiple scenarios by changing the loan term or interest rate to find the best combination of monthly payment and total interest cost for your customer's budget.
Use Cases
Presenting Zero-Down Financing
Show customers that a zero-down solar loan results in a monthly payment lower than their current utility bill - a cash flow positive day one with no upfront investment.
Comparing Loan Terms
Show a customer the tradeoff between a 12-year loan (higher monthly payment, less interest) and a 25-year loan (lower payment, more total interest) to match their budget priorities.
ITC Paydown Strategy
Model the ITC as a Year 1 principal paydown to show how applying the tax credit to reduce the loan balance lowers long-term interest and shortens the effective loan term.
Calculation Methodology
Standard amortizing loan calculations form the basis, with incentive timing adjustments applied to model real solar financing structures.
Monthly Payment
PMT = P × [r(1+r)^n] ÷ [(1+r)^n − 1]
Standard amortization formula. P = loan principal, r = monthly rate (annual rate ÷ 12), n = total months.
Effective System Cost
Effective Cost = System Cost − ITC Value − State Credits − Rebates
The true out-of-pocket cost after all incentives, used to express what the customer actually pays for the system over the financing period.
Monthly Net Cash Flow
Net Cash Flow = (Annual Savings ÷ 12) − Monthly Payment
Positive net cash flow means the system pays for itself immediately. Negative means the customer's total monthly cost is higher than before solar during the loan period.
Total Interest Paid
Total Interest = (Monthly Payment × n) − Loan Principal
The total dollar cost of financing above the principal - the amount by which financing increases the total system cost versus a cash purchase.
Pro Tips
Lead with monthly net cash flow, not payback period. For financed customers, the payback period concept is less intuitive than "your loan payment is $120/month and your current bill is $180/month - you save $60 from day one." Monthly cash flow is the most persuasive number in solar financing conversations.
Model the ITC paydown at month 18, not Year 1. Most solar-specific loans (Mosaic, GoodLeap, Sunlight) have a 30% ITC paydown feature: if the customer doesn't apply their tax refund to the loan by month 18, the loan is re-amortized at a higher effective rate. Make sure the customer understands this and plans to pay down the principal with their tax refund.
A 25-year loan minimizes monthly payment but maximizes interest. On a $25,000 loan at 6.99%, a 25-year term costs about $9,500 more in total interest than a 12-year term. If the customer can handle a higher payment, a shorter term delivers significantly better 25-year economics.
Dealer fees increase the real cost of "low-rate" loans. Some lenders offer 0.99% or 1.49% loans but charge the installer a dealer fee of 20–30% of the loan amount, which is typically passed to the customer in the system price. Compare the all-in cost, not just the stated interest rate.
Frequently Asked Questions
What is a typical solar loan interest rate in 2026?
Solar-specific loans from lenders like Mosaic, GoodLeap, and Sunlight Financial typically range from 3.99% to 8.99% APR depending on the loan term and borrower credit score. Conventional home equity loans or HELOCs may offer lower rates for homeowners with significant equity. Credit union personal loans often fall in the 6–10% range.
Is it better to pay cash or finance solar?
Cash purchases deliver the best 25-year return because there is no interest expense. However, financing allows customers to install solar with no upfront cost and often achieve day-one savings if the loan payment is less than their current utility bill. The right choice depends on available capital, opportunity cost, and monthly budget priorities.
What is the ITC paydown feature on solar loans?
Many solar-specific loans are structured with a higher initial payment that drops once the customer applies their federal tax credit to the loan principal. If the customer doesn't make this ITC payment within 12–18 months, the loan re-amortizes at a higher effective rate. Always explain this feature clearly during the sales process.
Can I use a HELOC to finance solar?
Yes. A home equity line of credit often has lower interest rates than solar-specific loans (typically 6–8% in 2026) and the interest may be tax-deductible if used for home improvement. The drawback is that a HELOC uses your home as collateral, whereas solar-specific loans are typically unsecured.
How does loan term affect total cost?
Longer terms lower monthly payments but significantly increase total interest paid. A $25,000 loan at 6.99% costs roughly $27,800 total over 12 years versus $37,300 over 25 years - a $9,500 difference in interest. Shorter terms save money but require higher monthly payments.
Does financing affect the ITC amount?
No. The ITC is calculated on the full installed system cost regardless of how the system is financed. A $30,000 system qualifies for a $9,000 ITC whether the customer paid cash or took a loan. The ITC amount is the same either way.
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