Solar Loan Monthly Payment Calculator

Enter your loan amount, interest rate, term, and current electricity bill to calculate your monthly solar loan payment, net savings, and full amortization schedule.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Enter Loan Amount
Input the total amount you are borrowing to finance your solar installation.
2
Specify Interest Rate
Provide the annual interest rate on your solar loan. Rates typically range from 4% to 10%.
3
Define Loan Term (yrs)
Enter the number of years over which you plan to repay the loan. Common terms are 10, 15, or 20 years.
4
Input Current Electricity Bill
Provide your average monthly electricity bill before installing solar. This is used to calculate cash flow and savings.
5
Review Your Loan and Savings Projections
Examine your calculated monthly payment, total interest paid, lifetime electricity savings, and cashflow breakeven point.

Example Calculation

A homeowner takes out a $20,000 solar loan at 6.5% interest over 15 years, with an average pre-solar electricity bill of $150/month.

Loan Amount ($)

20,000

Interest Rate (%)

6.5

Loan Term (yrs)

Current Electricity Bill ($)

150

Results

$174.45

Tips

Compare Loan Offers Carefully

Solar loan interest rates and terms can vary significantly between lenders. Shop around for the lowest rates, as even a 1% difference on a $20,000 loan over 15 years can save you over $1,800 in total interest paid.

Factor in the Federal Tax Credit

Remember that the federal Investment Tax Credit (ITC), currently 30% through 2032, can significantly reduce your net system cost. Many homeowners use this credit to pay down a portion of their loan principal in the first year, reducing subsequent interest payments.

Understand Cashflow Breakeven

The cashflow breakeven indicates when your monthly loan payment plus reduced utility bill equals your original utility bill. Aim for a positive cashflow from month one (loan payment < original bill) to maximize immediate savings and avoid an increase in monthly expenses.

Financing Solar: Calculating Your Monthly Loan Payments and Savings

The Solar Loan Monthly Payment Calculator helps homeowners understand the financial implications of financing a solar energy system. It determines the monthly loan payment, total interest accrued, and provides insights into lifetime electricity savings and the cashflow breakeven point. For example, a $20,000 solar loan at 6.5% over 15 years would result in a monthly payment of approximately $174.45, allowing homeowners to compare this new expense against their previous electricity bills and project significant long-term savings.

Understanding Solar Loan Structures

Solar loans are a popular financing option, allowing homeowners to own their solar systems without a large upfront capital outlay. These loans typically feature fixed interest rates and terms ranging from 10 to 20 years, making monthly payments predictable. Unlike leases, owning the system means homeowners retain eligibility for the federal Investment Tax Credit (ITC), currently 30% through 2032, and other local incentives. Many lenders cap debt-to-income (DTI) ratios for solar loans at around 40-45%, similar to mortgage underwriting, to ensure affordability.

The Amortization Formula for Solar Loans

This calculator employs the standard loan amortization formula to determine the fixed monthly payment required to fully repay the loan amount, including principal and interest, over the specified loan term. It then uses this monthly payment, alongside your current electricity bill, to project your monthly savings and the cashflow breakeven point, illustrating when your new combined costs (loan + reduced bill) are less than your old bill.

monthly payment = loan amount × [monthly interest rate × (1 + monthly interest rate)^number of payments] / [(1 + monthly interest rate)^number of payments – 1]

Here, monthly interest rate is the annual rate divided by 12, and number of payments is the loan term in years multiplied by 12.

💡 Understanding the financial impact of environmental choices is increasingly important. Our CO2 Emissions from Electricity Calculator helps quantify your carbon footprint reduction from solar.

Projecting a Solar Loan's Financial Impact

Let's consider a homeowner taking out a solar loan:

Loan Amount: $20,000
Interest Rate: 6.5% (annual)
Loan Term: 15 years
Current Electricity Bill (monthly): $150

Calculate Monthly Payment: Using the amortization formula, the monthly payment for a $20,000 loan at 6.5% over 180 months (15 years) is calculated to be approximately $174.45.
Determine Total Interest: Over 15 years, the total interest paid would be around $11,400.
Project Monthly Savings: If the solar system eliminates the $150 monthly bill, the homeowner's net cashflow for energy would be -$24.45 ($174.45 loan payment - $150 old bill). However, if the solar system significantly reduces the bill (e.g., to $20), the monthly savings are calculated as $150 - $20 = $130, and the new total cost is $174.45 + $20 = $194.45.
Cashflow Breakeven: The calculator would show the point at which the new combined monthly energy cost is less than the original $150 bill, indicating when the homeowner starts experiencing positive cash flow.

The primary result is a Monthly Payment of $174.45.

💡 For other cost-per-unit calculations, such as those in industrial applications, our Chemical Cost per Treatment Calculator provides a similar approach to financial analysis.

When a Standard Loan Model Falls Short

While solar loans are generally effective, a standard amortization model might not fully capture all nuances for specific solar financing scenarios. For example, some "zero-down" solar loans might have a balloon payment or a re-amortization requirement after the federal Investment Tax Credit (ITC) is received, typically in the first 12-18 months. If the ITC is not applied to the principal at that point, monthly payments can increase significantly. Additionally, the standard model doesn't account for property tax increases (if the system isn't exempt) or potential income from selling Solar Renewable Energy Credits (SRECs), which can vary by state, like the SREC market in Massachusetts which can add $200-$400 per year in income. Always confirm the specific terms of your solar loan agreement beyond the basic payment schedule.

Frequently Asked Questions

How is a solar loan monthly payment calculated?

A solar loan monthly payment is calculated using a standard amortization formula, considering the loan amount, annual interest rate, and loan term in months. The formula ensures that each payment covers both a portion of the principal and the accrued interest. For example, a $20,000 loan at 6.5% over 15 years would result in a monthly payment of approximately $174.45, gradually reducing the principal balance over the 180 payments until the loan is fully repaid.

What is cashflow breakeven for a solar loan?

Cashflow breakeven for a solar loan is the point at which your new total monthly housing expense (solar loan payment + reduced electricity bill) becomes equal to or less than your original average electricity bill before solar. Achieving a positive cashflow from month one, where your new combined expenses are immediately lower, indicates an excellent financial outcome. This metric helps homeowners understand when they start saving money each month by going solar.

How does a solar loan affect your total lifetime savings?

A solar loan can significantly impact your total lifetime savings by allowing you to finance a system that generates free electricity, offsetting expensive utility bills. While you pay interest on the loan, the savings from solar often outweigh the loan costs, especially with rising electricity rates. Over a 20-25 year system lifespan, even with a loan, homeowners can expect to save tens of thousands of dollars compared to continuously paying for utility power, often achieving net savings of $30,000-$60,000.