Solar
Solar Loan Calculator
Solar loan payment follows standard amortization using the financed principal, APR, and term. Dealer fees and any independently verified principal lump sum remain visible inputs. The method follows the displayed amortization or cash-flow equations and the dated IRS or contract-source boundaries linked on the page.
Estimate a solar loan payment, dealer-fee-adjusted principal, total payments, bill comparison, and an optional verified principal lump sum.
Calculated result
Solar loan scenario
Calculating…
Calculated locally in your browser
Planning math only. Verify equipment specifications and installation requirements separately.
Data provenance: NLR PVWatts v8 grid awaiting its first private-key refresh; the visible peak-sun-hours fallback is active. EIA residential state averages updated 2026-08-13. ZIP centroids use the 2025 Census Gazetteer. Calculator lookups use checked-in data rather than sending inputs to those source agencies; information submitted through quote or email forms is handled under the Privacy policy. Read the solar data provenance and limitations.
Policy snapshot 2026-08-13: The optional principal lump sum defaults to zero. IRS Form 5695 instructions state that residential clean-energy credits cannot be claimed for expenditures after December 31, 2025. Confirm your own facts professionally.
What this calculator returns
Use this as a nominal amortization comparison. Obtain lender disclosures showing financed amount, APR, fees, payment schedule, prepayment terms, and whether recasting is offered.
Formula and variables
The calculation runs entirely in your browser. Static formulas, definitions, examples, and tables remain readable without JavaScript.
Payment = principal × monthly rate / [1 − (1 + monthly rate)^−months]. Financed principal includes the entered dealer fee; the recast scenario subtracts the entered lump sum.
- P
- Cash price or financed principal, as identified by the input.
- r
- Entered monthly interest rate derived from APR.
- n
- Number of scheduled monthly payments.
- g
- Entered annual lease, PPA, or utility escalation rate.
- E
- Entered annual solar energy used only in the PPA and utility scenarios.
APR, term, dealer fee, bill, and lump sum are user-entered. No tax credit, rate offer, or lender term is assumed.
Worked example
| Input | Value |
|---|---|
| Quoted system amount | 20000 $ |
| Loan term | 10 years |
| Annual percentage rate | 6 % |
| Dealer fee added to principal | 10 % |
A $20,000 quote with a 10% dealer fee creates $22,000 financed principal. At 6% for 10 years, the calculated payment can be compared with both the entered bill and a zero-default lump-sum scenario.
Reference table
| Term | Calculator treatment | Verify in documents |
|---|---|---|
| APR | User entered | Truth-in-lending disclosure |
| Dealer fee | Added to financed principal | Cash price versus financed price |
| Escalator | Compounds annually | Lease or PPA contract |
| Principal lump sum | Zero by default | Eligibility and lender recast terms |
Frequently asked questions
How does a dealer fee affect solar financing?
The entered dealer-fee percentage increases financed principal before the payment is amortized.
What does the lump-sum recast scenario show?
It subtracts the entered lump sum from principal and recalculates a nominal payment; it does not claim that a lender permits recasting.
Does the calculator assume a federal residential solar credit?
No. The default lump sum is zero; use the dated IRS snapshot linked on the page and confirm your own eligibility.
Assumptions and limitations
- Not financial, tax, legal, or investment advice.
- No lender offer, approval, tax benefit, savings forecast, or equipment performance is represented.
- Payments exclude taxes, insurance, maintenance, interconnection, and changing utility charges.
- Policy assumptions are tied to the dated source snapshot shown on this page.
Method and sources
Review the solar data sources, calculation methodology, and electrical formulas for the references most relevant to this calculation. The broader technical sources index records source scope and provenance. Content release .
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