Loan audit · the cash-vs-financed gap
Solar loan calculator — find the financing markup.
Type the cash price and the financed total from your proposal. We decompose the gap into stated-APR interest vs unexplained markup — the residue that, per LBNL1, often reflects a dealer fee or financing markup the installer pays the lender and rolls into your "cash" quote.
Updated May 16, 2026.
Find the gap
If the financed total is materially above the cash price, do not debate the monthly payment first. Ask for the cash-only price for the identical system and the Truth-in-Lending disclosure showing amount financed, finance charge, APR, and total of payments.
Your loan — type the numbers from the proposal
Audit result — the gap explained
Total financed payments 20.1% above cash — inside LBNL's documented 5-50% dealer-fee range. Berkeley Lab: financed solar prices "likely include dealer fees, adding anywhere from 5-50% to the total up-front price paid by the customer." Ask for a cash-only quote that excludes any dealer fee.
What this audit can't see
The contract's actual TILA box (look there for the official APR, finance charge, amount financed, and total of payments). Prepayment penalties. Loan re-amortization clauses. Whether the dealer fee is paid by the installer to the lender or built into a separately-amortized payment stream. The calculator computes the gap; the loan paperwork explains who pays what.
Cash price vs financed price.
The headline computation is the gap between cash price and total financed payments. Berkeley Lab's Tracking the Sun 2024 report1documents that financed solar prices "likely include dealer fees, adding anywhere from 5-50% to the total up-front price paid by the customer." The 5-50% range is our verdict band.
The secondary computation is "how much of the gap is real interest vs unexplained markup." We compute what the loan total would beif the lender truly amortized the cash price at the stated APR — call it APR-predicted total. The difference between APR-predicted and the actual financed total is the unexplained markup. Positive values mean the lender is using a smaller principal than the cash quote — a spread that often reflects a dealer fee or financing markup, even when the proposal doesn't name it.
This calculator now owns the dealer-fee topic. The next action is direct: ask the installer for a cash-only quote for the identical system and compare it against the financed total shown here.
- 1. Berkeley Lab, "Tracking the Sun, 2024 Edition" (Executive Summary, August 2024; data through year-end 2023; sample ~3.7M U.S. distributed PV systems). State-level median residential installed price in 2023: $3.20–5.20/W. Loan dealer-fee gap, verbatim: "a large portion of residential systems are loan-financed, and installed prices reported for these systems likely include dealer fees, adding anywhere from 5-50% to the total up-front price paid by the customer." Verified 2026-05-16. emp.lbl.gov · Tracking the Sun 2024 (PDF) ↩
Next: Run the full quote audit — the gap test above is one of six checks the flagship calc runs.