Solar Loans, Cash, or HELOC: Which Financing Costs You Least?

Almost every residential solar quote you see assumes a specific loan product, usually from GoodLeap, Sunlight Financial, Dividend, or Mosaic. These products are convenient and the homeowner never sees a separate fee. That is the problem. The fee is baked into the cash price quoted to you.

Here is how it works. A 1.99% APR 25 year loan exists, but the lender needs to make money. To compensate for the absurdly low advertised rate, the installer pays the lender a dealer fee of 20% to 35% of the project cost up front. That fee is added to your contract price. So a system that would cost $24,000 in cash gets quoted at $30,000 with the 1.99% loan. You pay the dealer fee whether you realize it or not.

Higher loan APRs come with lower or no dealer fees. A 7.99% loan on the same system might be quoted at $24,500. Yes, the monthly payment is higher, but the total cost over the loan term is often less because you are not financing the inflated price.

Always, always ask the installer for the cash price separate from the financed price. A reputable installer will give it to you without arguing. Then compare your real financing options against that cash number.

A home equity line of credit (HELOC) is currently one of the cheapest ways to fund solar for homeowners with equity and a decent credit score. HELOC rates as of late 2025 sit in the 8% to 9% range, the interest may be tax-deductible if the loan proceeds improve the home, and you avoid the dealer fee entirely. The math frequently beats the heavily marketed solar-specific loans.

Cash is almost always the cheapest option in absolute terms, but it is not always the smartest. If your alternative use for the cash earns more than the loan's effective rate, you should finance. Treasury bonds yielding 4.5% after tax beat a 7% loan only if the after-tax loan cost is below 4.5%, which it usually is not. The honest answer is that cash wins for most homeowners who have it sitting in a savings account earning nothing.

One trap to avoid. Many solar loans contain a 'reamortization' or 're-am' clause that assumes you will receive the federal tax credit and use it to make a balloon payment on the loan within 12 to 18 months. If you do not make that payment, your monthly payment jumps significantly because the loan is recalculated against the full balance. Read this clause carefully. If you do not expect to have the tax liability to claim the credit, this loan structure can produce a nasty surprise in month 19.

The simple decision framework: get a cash price first, then evaluate three financing paths against it. Solar loan, HELOC, cash from savings. Pick whichever has the lowest total cost over the period you actually plan to keep the money tied up.