Reading your HELOC cost result
Why the payment jumps sharply at repayment
During the draw period, many HELOCs only require interest payments, which keeps the monthly cost low but doesn't reduce the balance at all. Once repayment begins, the full principal has to amortize over a much shorter window than a typical solar loan, so the payment often jumps by 30% to 50% or more. On a $28,000 draw at 8.25%, that's a move from about $193 a month to roughly $272 a month. The CFPB's HELOC explanation covers this two-phase structure in more depth.
How a HELOC compares to a dedicated solar loan
A HELOC can offer a lower rate since it's secured by your home, but that security is also the risk: your home backs the debt, unlike most unsecured solar loans. The secured vs unsecured comparison walks through that tradeoff directly. Whether a federal tax credit applies to your system depends on its installation date, not on which loan type you choose to finance it.
What a variable rate means for your total cost
This calculator assumes your current APR holds steady across both periods, but HELOC rates typically float with the prime rate and can move up or down over a 10 or 15-year draw period. Build in some cushion above your current rate when budgeting, since a 1 to 2 point rate increase partway through the draw period would raise both the interest-only payment and the eventual repayment amount. The CFPB's issue spotlight on solar financing covers general financing considerations worth reviewing alongside this one.
How much home equity you'll need
Lenders typically cap total borrowing, including your first mortgage and the HELOC, at 80% to 85% of your home's value. The loan to value calculator shows whether your available equity covers the system cost before you apply. The combined roof and solar financing tool is also worth checking if you're bundling a roof project into the same equity draw.
Whether paying down principal early during the draw period helps
Even though only interest is required, most HELOCs let you pay down principal voluntarily during the draw period, which reduces both the ongoing interest and the balance due at repayment. If you can afford payments above the interest-only minimum, that extra goes directly to reducing what you owe when the higher repayment-period payment kicks in. The early payoff savings calculator shows this same principle applied to a standard solar loan. The total cost of ownership calculator can help you see how this fits into your broader ownership costs.