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Solar Refinancing Calculator

Refinancing your solar loan to a HELOC or home equity loan? Enter your loan details and new rate — get monthly savings, interest saved, and break-even timeline.

Current solar loan
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months
Refinancing details
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Refinancing analysis
Save $26.41/mo — Worth it
Current monthly payment$332.98/mo
New monthly payment$306.57/mo
Monthly payment savings$26.41/mo
Total interest saved$7,290
Total fees (closing + prepay)$2,500
Net benefit after fees$4,790
Break-even (closing costs recovered)7.9 yrs (95 mo)
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How to Use This Calculator

Enter your current solar loan details

Find your current loan balance on your most recent loan statement or servicer portal. Your interest rate is in your original loan agreement — look for "APR" or "interest rate." Months remaining is your remaining term: if you have a 25-year loan and have paid 2 years, you have 276 months remaining.

Enter refinancing details

Select the new loan product you're considering. HELOCs (Home Equity Lines of Credit) typically have variable rates around 6-8% depending on prime rate. Home equity loans offer fixed rates around 7-8.5%. Enter your expected closing costs — get actual quotes from 2-3 lenders before finalizing. Check your original solar loan for any prepayment penalty language.

Check the PACE flag if applicable

If your solar system was financed through a PACE program (Property Assessed Clean Energy — also called HERO, Ygrene, or similar), check "Yes" for the PACE flag. Refinancing a PACE loan is more complex than a standard solar loan refinance and may have property tax implications in some states.

The Formula

Current Monthly Payment = Balance × (r_cur / (1 - (1+r_cur)^-n)) New Monthly Payment = Balance × (r_new / (1 - (1+r_new)^-n)) Monthly Savings = Current Monthly − New Monthly Total Current Interest = Current Monthly × Months − Balance Total New Interest = New Monthly × Months − Balance Interest Saved = Total Current Interest − Total New Interest Total Fees = Closing Costs + Prepayment Penalty Net Benefit = Interest Saved − Total Fees Break-even Months = Total Fees ÷ Monthly Savings

The break-even calculation is the most important output. If closing costs are $2,500 and you save $48/month, you break even in ~52 months (4.3 years). If you only have 5 years left on the loan, this refi barely makes sense. If you have 22 years left, you gain 17+ years of savings after break-even — a compelling case.

Example

Tom — 2 years into a 25-year solar loan at 7.99%

Tom took a solar loan 2 years ago at 7.99% APR. His balance is $42,000 with 276 months remaining. He's considering a HELOC at 7.0% with $2,500 closing costs and no prepayment penalty.

Current balance$42,000
Current rate7.99% APR
Months remaining276 months (23 years)
New rate (HELOC)7.0% APR
Closing costs$2,500

Result

Current monthly payment$319/mo
New monthly payment$298/mo
Monthly savings$21/mo
Total interest saved~$6,900
Net benefit after fees~$4,400
Break-even~10 years

Tom's refi saves him $21/month but takes 10 years to break even on closing costs. With 23 years remaining, he does come out ahead — but barely. If the HELOC rate rises by 1% due to Fed moves, the calculus quickly reverses. This scenario shows that a 1% rate reduction is marginal for early refinancing.

FAQ

Yes — if you have sufficient home equity, you can use a HELOC to pay off your existing solar loan balance and replace it with the HELOC. The benefit: HELOCs are borrowed against the actual home value, not an inflated solar loan principal — so you're only borrowing what you truly owe. The key requirements: you need at least 15-20% equity in your home after the HELOC (most lenders cap combined LTV at 80-85%), and your credit score should be 680+ for competitive rates. Contact 2-3 local credit unions alongside national lenders for quotes.
PACE (Property Assessed Clean Energy) loans are attached to your property as a tax assessment — they're paid through your property tax bill, not your bank account. They survive home sales (transferring to the new owner unless paid at closing). Refinancing a PACE loan is different because: (1) You must pay off the PACE assessment in full at refi — you can't partially roll it over. (2) In California, paying off a PACE assessment before the original term may trigger a Prop 13 reassessment of your home's value. (3) Some mortgage lenders won't originate a HELOC on homes with existing PACE assessments. Always consult a real estate attorney in your state before refinancing a PACE loan.
Earlier is almost always better — if the rate difference justifies it. In the first 1-5 years, you have maximum remaining principal and maximum remaining interest, so even a small rate reduction saves a significant total amount. By year 18-20 of a 25-year loan, your remaining balance and interest are small enough that closing costs may never be recouped. The rule of thumb: refinancing typically makes financial sense if you have more than 10 years remaining and can reduce your rate by at least 0.75-1.0 percentage points.
Under current IRS rules (post-2017 Tax Cuts and Jobs Act), HELOC interest is tax-deductible only if the loan proceeds are used to "buy, build, or substantially improve" your home. Solar panels installed on your home may qualify — the IRS has issued guidance that solar panels are a home improvement. However, this is an evolving area and depends on your specific situation. Consult a tax advisor before assuming deductibility. If you itemize deductions and are in the 22-24% tax bracket, deductible HELOC interest at 7% effectively costs 5.3-5.5% after tax — a meaningful improvement.

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<iframe src="https://solarsizecalculator.com/solar-refinancing-calculator"
  width="100%" height="620" frameborder="0"
  title="Solar Refinancing Calculator"></iframe>