Start with two numbers: cash price and financed principal
Ask the installer for the cash price of the identical solar equipment and scope, then compare it with the amount the lender will actually finance. The difference is not automatically all dealer fee, but it is the first discrepancy to explain before signing.
Home Solar Atlas calls the percentage difference a loan premium versus cash only when the financing type is a confirmed loan. It is a normalization aid, not a legal determination of which specific fee caused the difference.
CFPB found substantial hidden markups in some solar-specific loans
The Consumer Financial Protection Bureau reported in its solar-financing issue spotlight that some lenders include substantial markups and fees that can increase loan principal by 30% or more above the cash price. The CFPB describes industry labels including dealer, program, lending, finance and platform fees.
That makes the cash-price comparison essential even when a salesperson emphasizes a low APR or a monthly payment designed to resemble the homeowner's utility bill.
APR and principal answer different questions
APR is an important credit disclosure, but a homeowner also needs to know whether the project price was increased before the loan began. Two loans can have different APRs and different principals, so comparing only the advertised rate can hide a much more expensive underlying financed amount.
Record cash price, financed principal, APR, term and total scheduled payments together. If the lender or installer cannot explain a large cash-to-financed gap, treat that as an unresolved proposal question rather than as a normal solar cost.
Do not subtract the expired homeowner credit to create a sales-only net cost
The IRS says Section 25D is not allowed for expenditures made after December 31, 2025. For a new 2026 residential installation, do not hide the financed principal by presenting a hypothetical old 30% homeowner federal credit as though it were guaranteed cash reducing the loan.
Evaluate verified state, local and utility incentives separately. A financing comparison should still show the actual cash-equivalent project price and actual financed principal before uncertain benefits are applied.
Watch for re-amortization and payment step-ups
Some solar loans pair an expected early principal payment with a later payment recalculation. Dealer/program fees and re-amortization are separate issues: a loan can contain both. Model the payment if the expected principal reduction is made and the payment if it is not.
Compare solar $/W from the cash-equivalent solar price
For installer comparison, calculate solar $/W from the positive solar-only cash-equivalent project price, not from a loan amount inflated by financing. Keep batteries and separately itemized non-solar work out of the solar-only numerator when those amounts are genuinely included in the project total.