Flagship audit · the quote calculator
Solar quote calculator — audit the proposal before you sign.
For homeowners with a residential solar proposal in hand. Type the numbers from the proposal; we benchmark every line against NREL PVWatts (production), LBNL Tracking the Sun (installed cost), and the IRS Form 5695 placed-in-service cutoff (tax credit), then flag where the math breaks. If you're still deciding whether to install and what size, start with the solar panel calculator instead.
Updated May 16, 2026. Sources re-verified the same day; methodology below.
Before you start, pull the proposal: kW DC and year-1 production kWh from the system-summary page, cash and financed totals from the price stack, the “−30% federal credit” line and projected install year from the contract front page.
Audit docket · Quote file
Residential · tax-credit timing · public-data benchmarked
01 / Input
Proposal numbers
System kW · year-1 production kWh · cash $ · financed $ · payback claim · credit line · install year.
02 / Benchmark
Public-data spine
- LBNL Tracking the Sun — $/W band
- NREL PVWatts — production
- IRS Form 5695 — §25D cutoff
03 / Output
Line-by-line verdict
- Green — plausible
- Amber — verify
- Red — get it in writing
04 / Action
Before you sign
Take the red lines back to the installer — request a revised quote or a written answer in plain English on each flag.
Your quote — type in the numbers
Audit verdict — your quote vs benchmark
2 flagsWhat 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; ask the installer to confirm permitting and interconnection fees are inside the cash price.
- $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 markup. Check your state in our cost-per-watt guide.
- Above $5.20:exceeds LBNL's highest state median — get a second quote and ask the installer to itemize what's driving the price.
A note on vintage: the calculator uses the 2023 state-median band because that is the most recent Berkeley Lab dataset with state-levelthreshold boundaries. Berkeley Lab's newer 2025 Distributed Solar & Storage Data Update reports 2024 national medians of about $3.50/W cash and $4.70/W loan — we cite those for cash-vs-loan context in our cost-per-watt guide but the state band is what carries the verdict here.
State-level effects move the median by roughly $2/W. We do not automate state-specific cost or incentive math here; for incentives and net-metering rules, look up your state and utility on DSIRE and confirm your utility's export-credit tariff directly with the utility.
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. The loan calculator isolates the gap.
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. We use this as a sanity check, not an exact production target. 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. Either way, run your ZIP, tilt, and azimuth at pvwatts.nrel.gov; the proposal's year-1 kWh should land within roughly 10–15% of the PVWatts result. If the proposal sits higher, ask the installer for their PVWatts run or equivalent production model.
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 subtracts 30% on a 2026+ install is asserting a credit the homeowner cannot claim; ask for the projected placed-in-service date in writing and a revised proposal with the credit removed. Lease and PPA arrangements may still 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. Our tax credit checker resolves edge cases.
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 — start with the how-to-read-a-solar-quote companion guide if any line on the proposal is unfamiliar.
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 Sun1a 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 — ask for the cash price for the same system and the lender's Truth-in-Lending disclosure before signing.
- 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 ZIP, tilt, and azimuth at pvwatts.nrel.gov — your quote should land within roughly 10–15% of that number.
- 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 the payment by the term in months to reconstruct the loan total, then enter that. Without the loan-total figure, the dealer-fee gap LBNL documents stays invisible.
- Why does the audit care about my install year?
- Because a 2025 federal law change ended the federal Residential Clean Energy Credit (§25D) for systems placed in service after December 31, 2025 — see the IRS Form 5695 (2025) instructions3. “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 subtracts 30%, the math doesn't work as advertised. Our tax credit checker resolves the eligibility detail.
- What about state and utility incentives?
- Out of scope for this calculator — state credits, utility rebates, and net-metering rules change too quickly to encode reliably. For your state, look up DSIRE (the N.C. Clean Energy Technology Center's ZIP-searchable incentive database) and confirm your utility's export-credit tariff directly with the utility before trusting any bill-savings projection a proposal hands you.
- 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; 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) ↩
- 2. NREL PVWatts (v8) — annual production estimator using NSRDB irradiance data with default 14% total system losses (soiling, shading, snow, mismatch, wiring, connections, light-induced degradation, nameplate rating, age, availability). Typical US residential output: 1,000–1,600 kWh/kW annually. Verified 2026-05-16. pvwatts.nrel.gov · API docs ↩
- 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 §25D for systems placed in service after that date. Verified 2026-05-16. irs.gov/instructions/i5695 ↩