Flagship audit · the quote-checker

Solar quote checker — test the proposal.

For homeowners with a residential solar proposal in hand. Type the numbers on the page; we benchmark every line against NREL PVWatts (production), LBNL Tracking the Sun (installed cost), and the IRS Form 5695 cutoff (tax credit), then flag where the math breaks. To decide whether to install — and what size — start with the panel calculator instead.

Updated May 16, 2026. Methodology + sources below.

Your quote — type in the numbers

System sizekW DCEst. annual productionkWh/yrCash price$Financed pricesum of all loan payments (leave blank for cash-only)$Quoted payback periodfrom the proposal's payback claimyearsTax credit assumed in the quote?Install yearwhen the system will be 'placed in service'

Audit verdict — your quote vs benchmark

2 flags

Inside LBNL's documented 5–50% dealer-fee range — financed 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 price to confirm.

The federal Residential Clean Energy Credit (§25D) terminated for systems placed in service after Dec 31, 2025, per the IRS Form 5695 (2025) instructions, following a 2025 federal law change. A 2026 installation cannot claim the residential credit. Third-party-owned (lease/PPA) systems may capture credit value through the business-side §48E, but that doesn't put the 30% on the homeowner's tax return.

What this audit cannot see

Roof condition (age, layers, structural). Future shading from new trees or construction. Utility-specific time-of-use rate design or demand charges. Installer workmanship and warranty enforcement reality. Your tax liability (the credit is non-refundable). HOA, permitting, or interconnection delays. The calculator catches what's on paper. You catch what isn't.

How the audit thinks.

Every verdict in the table above is grounded in primary-source data. None of it is an industry rule of thumb. None of it is an installer benchmark. Where a range is given, the boundaries come from public reports we cite below.

Cash $/W: LBNL state-median band, 2023

Berkeley Lab's "Tracking the Sun" 2024 edition¹ reports that 2023 residential installed prices ranged from $3.20 to $5.20 per watt at the state-median level (host-owned, cash basis, inflation-adjusted). Verdicts:

Below $3.20: below LBNL's lowest state median — strong number, verify the cash price isn't omitting permitting / interconnection
$3.20–$4.20: lower half of the state-median band — reasonable in most states
$4.20–$5.20: upper half of the band — could be a high-cost state, could be a markup; check your state's specific median
Above $5.20: exceeds LBNL's highest state median — earn the price or negotiate

Dealer-fee gap: LBNL 5–50% range

LBNL's own language¹: "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." We treat the inflation between the cash price and total financed payments as the operative gap. Below 5% reads as real APR cost; inside the 5–50% range flags as likely dealer fee; above 50% exceeds LBNL's documented band and warrants direct investigation of the lender and the cash quote.

Production sanity: PVWatts typical US range

NREL PVWatts² uses NSRDB irradiance data with a default 14% total-system-losses assumption. For most US residential installations the annual output lands between 1,000 and 1,600 kWh per kW installed. Numbers below the range usually indicate cloudy climate, poor orientation, or heavy shading; numbers above the range usually indicate sunny Southwest installations — or inflated estimates. For either case, run your specific ZIP, tilt, and azimuth through PVWatts to verify before trusting payback math built on the production estimate.

Tax-credit eligibility: IRS §25D placed-in-service cutoff

The federal Residential Clean Energy Credit ended for systems placed in service after December 31, 2025, per the IRS Form 5695 (2025) instructions³. A 2025 federal law change set that placed-in-service deadline; §25D no longer applies to installations completed in 2026 or later. “Placed in service” is the IRS term for fully installed — not contract date, not deposit, not permit. A proposal that still assumes 30% on a 2026+ install is asserting a credit the homeowner cannot claim. Lease and PPA arrangements may capture credit value through the business-side §48E credit, but that money sits with the third-party owner, not on the homeowner's tax return.

What this audit cannot see

Roof condition, age, and layer count. Shading from future tree growth or new construction. Time-of-use rate design and demand charges specific to your utility. Installer workmanship and warranty enforcement reality. Your own tax liability — the §25D credit is non-refundable, meaning you need income tax owed to claim it. HOA, permitting, or interconnection delays. The calculator looks at numbers on paper. The rest is on you and your contract.

SizingSize a solar system →SensitivityStress-test the payback →FinancingTest the loan math →

Calculator FAQ.

What's the difference between cash $/W and financed $/W?: Cash $/W is the cash price divided by the DC system size — the cleanest cost comparator anyone can hand you. Financed $/W is the total of all loan payments divided by the same DC size. The gap between them is the true cost of financing, and per LBNL's Tracking the Sun¹ a 5–50% gap is the documented range for dealer-fee inflation in loan-financed residential systems. Above 50% and something more than financing is happening.
Where does the 1,000–1,600 kWh/kW typical range come from?: NREL PVWatts² models annual AC production from NSRDB irradiance data with a default 14% system-losses assumption (soiling, shading, snow, mismatch, wiring, light-induced degradation, age, availability). For most US locations with a south-facing residential roof, the output lands between 1,000 kWh/kW (cloudy northern climates with suboptimal orientation) and 1,600 kWh/kW (sunny Southwest with ideal tilt). Sunbelt installations can exceed the top of that range; if yours does, run your specific ZIP through PVWatts to confirm the estimate is real.
My proposal doesn't show a financed price. What goes in that field?: Leave it blank. The dealer-fee gap row disappears and the audit evaluates the cash quote on its own. If you're being shown only a financed monthly payment, multiply by the term in months to get the loan total, then enter that number. Knowing the loan-total figure is the only way to surface the dealer-fee gap LBNL documents.
Why does the audit care about my install year?: Because the federal Residential Clean Energy Credit (§25D) ended for systems placed in service after December 31, 2025 per the IRS Form 5695 (2025) instructions³. A 2025 federal law change moved that placed-in-service deadline. “Placed in service” is IRS-defined as the day installation is fully complete — not contract date, not deposit, not permit. If a 2026+ proposal still bakes in the 30%, the math doesn't work as advertised.
What does this audit miss?: Quite a bit — by design. The calculator catches what's on paper. It does not see roof condition, future shading from new trees or construction, utility-specific time-of-use rate design, demand charges, installer workmanship, warranty enforcement reality, your own tax liability (the credit is non-refundable), or HOA / permitting / interconnection delays. The audit narrows the search to numerical flags; the rest is on you and your contract.

1. Berkeley Lab, "Tracking the Sun, 2024 Edition" (Executive Summary, August 2024). State-level median residential installed price in 2023: $3.2–5.2/W. Dealer-fee range, 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 Executive Summary (PDF) ↩
2. NREL PVWatts (v8) calculator and API documentation. Annual production estimate uses NSRDB irradiance data and a default total-system-losses value of 14% (composed of soiling, shading, snow, mismatch, wiring, connections, light-induced degradation, nameplate rating, age, and availability). Verified 2026-05-16. pvwatts.nrel.gov · API docs (v8) ↩
3. IRS Form 5695 (2025) instructions, verbatim: "You can't claim residential clean energy credits for expenditures made after December 31, 2025." The One Big Beautiful Bill Act, signed July 4, 2025, terminated the residential clean energy credit (§25D) for systems placed in service after that date. Verified 2026-05-16. irs.gov/instructions/i5695 ↩

Ask a TrueSolarCost question

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.