Mechanism guide · the cash-vs-financed gap

Why a "low APR" solar loan can cost more than cash.

Updated May 16, 2026. The LBNL dealer-fee range is anchored to the most recent Tracking the Sun edition; we re-verify when Berkeley Lab updates the report.

Two prices on the same proposal. Same panels, same inverters, same roof. The cash price reads $31,800. The financed total — sum of every payment over a 25-year loan at a teaser APR — reads $38,200. That's a $6,400 gap before interest does anything; that's the salesperson's favorite math. The gap is also the most revealing number in the entire document, because Berkeley Lab's own data¹ says financed solar prices "likely include dealer fees, adding anywhere from 5-50% to the total up-front price paid by the customer."

The teaser APR isn't a gift. The financed quote isn't the cash quote plus interest. Most often the gap is a dealer fee— money paid by the installer to the lender so the lender can offer a below-market rate. Here's how the mechanism works, what to look for, and how to test your quote.

What a dealer fee actually is

A dealer fee, in solar-loan context, is a fee the installer pays the loan provider — typically 15–30% of the system price for a 20-25 year loan, sometimes higher — in exchange for the lender offering a below-market interest rate to the homeowner. The installer doesn't absorb that cost. It gets passed back to the customer through an inflated cash price quoted alongside the loan.

The structure: an installer's "real" price might be $26,000 for an 8.4 kW system. To offer a 1.99% APR loan on that system, the lender charges the installer a 22% fee — about $5,800. The installer can't eat that. So the "cash" price on the proposal becomes $31,800, the lender gets paid out of that spread, the homeowner's monthly payment looks cheap, and the $5,800 dealer fee is silently rolled into the financed total.

From the homeowner's side, the cash price doesn't look like a marked-up price. It looks like the price. The salesperson rarely volunteers the breakdown.

Why the teaser APR exists at all

Solar loans compete with auto loans, personal loans, and home equity for the same dollar of monthly consumer credit. To win the comparison, solar lenders advertise APRs that look extraordinary — 0.99%, 1.49%, 1.99% — across 20- and 25-year terms. No regulated lender writes profitable 25-year unsecured consumer credit at 2%. The math doesn't pencil out unless something else funds the spread. That something is the dealer fee.

Berkeley Lab is unusually direct about this for an academic institution¹: "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." Five to fifty percent. The wide range reflects different lenders with different fee schedules, but a typical mainstream solar loan in 2026 carries a dealer fee in the 15–30% range. Higher on longer terms and lower APRs.

A worked example

Consider a homeowner with a single quote for an 8.4 kW DC system:

• Cash price: $31,800 ($3.79/W)
• Financed price: $38,200 (sum of monthly payments over 25 years at 1.99% APR)
• Gap: $6,400, or 20.1% above the cash price

20.1% lands inside Berkeley Lab's 5–50% dealer-fee range, which is the signal that the gap likely isn't just interest. To verify: at a true 1.99% APR over 25 years on a $31,800 principal, total interest would be roughly $8,500 — meaning the financed price should be near $40,300, not $38,200. The financed number coming in $2,100 belowthat means either (a) the lender is taking a loss for goodwill — unlikely — or (b) the actual cost basis the lender is using is lower than the homeowner's cash price, with the dealer fee making up the spread.

Translation: the installer's "real" price was somewhere around $26,000. The cash price you saw is the real price + dealer fee + a margin. The financed price is the real price + real loan interest. You're comparing two different products that the proposal is presenting as the same product.

How to test your own quote

Three steps. Two are simple division. The third is a direct ask.

1. Compute the gap.(Financed total − cash price) ÷ cash price × 100. Anything from 5% to 50% lands inside LBNL's documented dealer-fee range.
2. Estimate the "true" interest. Use any amortization calculator (or our solar loan calculator (in the queue)) to figure out what the financed total should be at the quoted APR. If the actual financed number on the proposal is meaningfully lower than that — by more than ~5% — the cash price is inflated.
3. Ask for an itemization. Direct quote you can paste into an email: "Please provide a cash-only quote that excludes any dealer fee, financing fee, or origination charge paid to a lender, and confirm in writing that this number reflects the actual system cost before financing structures are applied." The response tells you whether the seller is configured to quote cash honestly. Some are. Many aren't.

What the loan paperwork is supposed to tell you

Federal Truth in Lending Act (TILA) disclosure requires solar loans to surface APR, finance charge, amount financed, and total of payments in a standardized format. The required disclosures are often called the TILA box — a small section of the loan contract showing those four numbers.

The number to focus on is "total of payments"— the sum of every payment you'll make over the life of the loan. Compare it against the cash price on the same proposal. The TILA box won't name a dealer fee (lenders aren't required to break it out), but the gap will be visible. If "total of payments" minus cash price exceeds plausible interest for the stated APR and term, you've found the markup.

When financing is actually cheaper

Not every solar loan hides a dealer fee. A small number of solar lenders write at-market rates with transparent origination fees, comparable to what you'd get refinancing a small mortgage. These exist and they're cleaner. The signal: financed total comes out 3–8% above cash price, the APR is in the 6–8% range (typical for unsecured consumer credit in 2026), and the lender will tell you the origination fee in plain numbers.

Home equity loans and HELOCs can also beat solar-specific loans on rate. They're secured by the home, which is its own risk consideration, but they don't carry dealer-fee structures. Worth shopping outside the installer's preferred lender if you're going to finance.

The cleanest move

Run the gap check on your quote. Run it in the quote calculator — it flags any financed gap in the LBNL band as "dealer fee likely" with the source citation inline. Then go back to the installer with a written request for the cash-only price. Three things happen: you find out whether the dealer-fee gap is real, you find out whether the installer will quote cleanly, and you give yourself room to negotiate the cash quote down by some or all of the spread. None of those outcomes are bad outcomes.

1. 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: The assumptions that quietly move your payback — what's inside the "7-year payback" figure.