This is an amortization and comparison tool, not a lending offer. Enter only incentives you have verified for your property and contract. Home Solar Atlas does not automatically apply the expired residential Section 25D federal credit to a 2026 project. The calculator caps a down payment at the modeled project amount and treats an optional early principal payment as a separate cash outlay.
Imported proposal values stay separate from fee assumptions
Quote Analyzer can transfer the current loan cash price, quoted financed amount and its reviewed meaning, APR, term, an explicitly quoted monthly loan payment, reviewed Number of Payments and Payment Frequency, an explicitly quoted Total of Payments and an explicitly quoted Finance Charge through browser session storage in the same tab. Missing transferred fields remain blank, so the calculator does not silently replace an unknown APR, loan term or payment-schedule reference with its normal demo assumptions.
The imported disclosure panel appears separately from the editable modeling inputs. That separation is deliberate: proposal or lender disclosures remain reference values, while the calculator below uses the assumptions you actually enter for amortization. Number of Payments and Payment Frequency are not substituted for modeled term or payment math.
A financed contract price, Regulation Z Amount Financed and a loan amount / principal are treated as three different concepts. Home Solar Atlas reconciles a confirmed financed contract price with the modeled project price and a confirmed loan principal with the modeled principal. Amount Financed stays visible as a disclosure reference and is not automatically treated as either of those values. Only a confirmed financed contract price can produce the optional cash-to-financed modeling-markup action.
An explicitly quoted Finance Charge is also preserved as a separate disclosure reference. Home Solar Atlas does not automatically relabel it as a dealer fee, compare it with the cash-to-financed contract-price markup, or declare it equal to modeled amortization interest. The written loan disclosure remains the controlling source for what the Finance Charge includes.
Payment count and frequency are not the whole payment schedule
Regulation Z payment-schedule review covers the number, amounts and timing of scheduled payments. Home Solar Atlas can preserve an explicitly quoted monthly payment, Number of Payments and Payment Frequency, but those references do not establish the full timing disclosure by themselves.
Verify the beginning-payment date or listed due dates in the original loan disclosure, along with any stepped payment amounts, promotional period, expected principal prepayment or re-amortization condition. The imported disclosure panel therefore keeps the payment-schedule item marked as Partial rather than declaring it complete.
Why compare quoted and modeled monthly payments?
When a proposal clearly states a monthly loan payment, the calculator can display it beside the payment produced by the cash price, fee assumption, down payment, verified incentives, APR and term currently entered here. The quoted payment remains a reference value and never replaces the amortization inputs.
A mismatch does not prove that the proposal is wrong. It can indicate a different financed principal, dealer or program fee, down payment, incentive treatment, payment step-up, expected early principal payment, re-amortization assumption, lender timing convention or another contract term. Home Solar Atlas does not reverse-engineer APR or hidden conditions from the quoted payment; use the difference as a prompt to reconcile the written financing documents.
Total of Payments is not total out-of-pocket
If the proposal explicitly states Total of Payments, Home Solar Atlas compares it only with the modeled sum of scheduled loan payments generated by the current principal, APR and term. A down payment is intentionally excluded from this disclosure reconciliation.
The calculator separately reports total out-of-pocket, which can include cash paid outside the scheduled loan payments. A mismatch in Total of Payments is therefore a prompt to check principal, APR, term, payment schedule, step-up or re-amortization conditions and lender timing—not a reason to force the disclosure to match by changing unrelated inputs.
Finance Charge is a separate Regulation Z disclosure
When the proposal explicitly states Finance Charge, the imported value is shown beside the other loan disclosures for review. It is intentionally not used to back-solve a dealer fee or hidden APR, and the calculator does not assume it equals the simple difference between modeled scheduled payments and modeled principal.
This keeps the disclosure visible without turning a legal disclosure definition into an unsupported modeling shortcut. Reconcile the quoted Finance Charge with the lender's disclosure and itemization rather than forcing the amortization model to reproduce it.
Why compare the loan against the cash price?
A solar proposal can advertise a low APR while increasing the financed system price with dealer, program or other financing fees. First identify whether a quoted financed number is the financed contract price, Regulation Z Amount Financed or the loan amount / principal. Compare a contract-price markup with cash only when the scopes actually match; keep Amount Financed, Finance Charge and principal separate, then review APR, term, scheduled payment and Total of Payments together. The CFPB has reported that some solar-specific loan markups can increase principal by 30% or more above the cash price.
How the re-amortization scenario works
Enter an optional early principal payment and the month when you want to test a recast. The calculator first models the original amortizing loan, calculates the remaining balance after the selected number of scheduled payments, applies the extra principal, and then recalculates the payment over the remaining scheduled term at the same APR.
This is an illustrative recast, not a statement that your lender must offer one. Some lenders keep the scheduled payment unchanged and shorten payoff instead; others have minimum principal amounts, timing rules or fees. Verify the actual loan documents before relying on the modeled payment.
Do not assume an old 30% federal credit will fund the early payment
For a new 2026 residential project, Home Solar Atlas leaves verified incentives at $0 by default. The IRS says the Section 25D Residential Clean Energy Credit is not allowed for expenditures made after December 31, 2025, and paying earlier does not preserve the credit when original installation is completed after that date. Enter only incentives you have separately verified for the property and contract.
Financing guides before you sign
Use this with the other Home Solar Atlas tools
Estimate first-year savings with the Home Solar Calculator, model long-term economics with the Solar Payback Calculator, check one contractor proposal with the Solar Quote Analyzer, or compare multiple proposals in Compare Solar Quotes.