Loan audit · the cash-vs-financed gap
Solar loan calculator — find the dealer fee.
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, is usually a dealer fee paid by the installer to the lender and rolled into your "cash" quote.
Updated May 16, 2026.
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.
How the calculator thinks.
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 be if 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 — the dealer fee funds that spread.
For the mechanism explainer — why this structure exists, when financing is actually cheaper, and how to ask for a clean cash quote — see the solar loan dealer fees guide.
- 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.
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Quick answers about TrueSolarCost's calculators, the public-data benchmarks, and how to read a residential solar proposal. Free, no signup. Not personalized advice — for tax-position questions talk to a CPA, for roof/structural questions talk to a roofer or engineer, for utility-rate questions talk to your utility.
Hi, I'm the TrueSolarCost assistant. I answer questions about how to read a residential solar proposal, what the calculators on this site compute, and what the public-data benchmarks (NREL PVWatts, EIA, IRS, LBNL, DOE, DSIRE) mean for the numbers in your quote. I'm not a tax professional, CPA, structural engineer, or licensed installer — for tax-position decisions talk to a CPA, for roof-condition or structural questions talk to a roofer or engineer, for utility-rate or interconnection specifics talk to your utility.