For homeowners with a solar proposal in hand
Check the solar quote before you sign.
TrueSolarCost tests system size, cost per watt, production claims, financing, incentives, batteries, and payback assumptions against NREL, EIA, IRS, LBNL, and DOE public data. Before you sign, not after.
A real 8.4 kW proposal, audited
Seven lines. Two worth a conversation before signing.
What this audit cannot see: roof condition, future shading, utility rate design, installer workmanship, your tax liability, HOA / permitting delays. The calculator catches what's on paper.
Start the audit
Pick the line on the quote you keep side-eyeing.
Is the system size reasonable?
Match the proposed kW against your actual annual usage and roof orientation. Oversized pads commission; undersized leaves money on the table.
Is the price per watt high?
Cash $/W is the cleanest comparator. LBNL's state medians live in a known band. Numbers outside it aren't wrong by default — but they earn a question.
Does the payback depend on perfect assumptions?
Rerun the payback with a realistic rate escalator and a conservative production number. If one input swings the headline year, it wasn't really a payback figure.
Is the loan hiding the true cost?
A low APR usually arrives with a dealer fee baked into the cash price. The gap between the cash-only price and the loan's total payments is the markup.
Calculators
Six tools the salesperson didn't bring.
Solar quote calculator
Type in the numbers on your proposal. We benchmark every line against public data and flag the math that doesn't survive scrutiny.
Solar panel calculator
How many panels you actually need — not how many the salesperson can fit.
Solar payback calculator
Payback math with the assumptions exposed. Move the escalator. Watch the year change.
Solar loan calculator
Strip the dealer fee out of the cash price. Find out what the loan really costs.
Solar tax credit checker
Is your 2026 proposal still pretending the 30% credit applies? Find out before you sign.
Solar battery calculator
Backup product or savings product? They're different math. Don't let one quote claim both.
Guides
The audit, written out.
How to read a solar quote
Five numbers decide whether the math holds up. Where each comes from — and how each misleads.
Solar cost per watt
What “fair” looks like in 2026, and where in a financed quote the markup likes to hide.
Solar loan dealer fees
The “no money down, 1.99% APR” loan can cost more than cash. The math that explains why.
Net metering vs net billing
Two compensation models, two different bills. The one your utility uses changes the payback by years.
Why your solar bill may not go to zero
Fixed charges, winter mismatch, and the asterisks proposals quietly drop. Yes, you'll still get a bill.
Solar sales red flags
Disappearing discounts. “Today only” incentive pricing. The pressure tactics worth walking out on.
Sourced from public data
Every benchmark, production estimate, and tax-credit eligibility check leans on a primary source — named inline on the page that uses it, with a verification date.
- ›NREL PVWatts — Annual production estimates by ZIP
- ›EIA — Residential utility-rate history
- ›IRS / DOE — Tax-credit eligibility + consumer-protection framing
- ›LBNL Tracking the Sun — Installed cost benchmarks
- ›DSIRE — State + utility incentive lookup
FAQ
What people google after the salesperson goes home.
- The proposal still assumes the 30% federal tax credit. Can I really use it in 2026?
- If your installation finishes in 2026 or later: no. The federal Residential Clean Energy Credit ended for systems placed in service after December 31, 2025 per the IRS Form 5695 (2025) instructions1. The 2025 federal law that ended the residential credit set that cutoff. “Placed in service” means the system is fully installed — not the day you signed, not the day a deposit cleared, not the day a permit was pulled. If an installer is still quoting 30% on a 2026 install, ask which section of the Code authorizes it.
- Why are the cash price and financed price so different?
- Because the cash price on a financed quote usually isn't the cash price. Many financed solar proposals inflate the cash figure by 15–35% and use that gap to subsidize a teaser-rate loan. The headline APR looks great; the dealer fee is what's actually paying for it. Ask for the cash-only price separately, divide by your system's DC kW, and compare $/W across quotes.
- Will the system actually pay for itself in 7 years?
- Maybe — and the difference is three numbers the proposal didn't show. Payback is a 25-year forecast resting on a production estimate, your current utility rate, and an assumed rate escalator. Recent EIA data3 shows residential rates rose 7.4% year over year through February 2026, but the 10-year trend is closer to 2–3%. Rerun the proposal with a conservative escalator and an aggressive one. If the payback year shifts by more than two, the headline number was a guess.
- Should I get more than one solar quote?
- At least three. The DOE Homeowner's Guide to Going Solar4calls pushy sales tactics a red flag and recommends NABCEP-certified installers. Three quotes also reveal the $/W spread in your area — the single most useful number in an audit. One quote isn't a market.
- Will my electric bill actually go to zero?
- Usually not. Three things keep a bill alive: fixed charges (connection fees, basic service), seasonal mismatch between summer production and winter use, and net-metering policies that credit your exports at less than retail rate. Bill savings are real. “Zero bill” is a sales line.
- Do I need a battery?
- Depends what you're buying. Batteries are excellent backup products. They're mediocre savings products in most markets — the financial payback needs steep time-of-use rate spreads or frequent outages to make sense. Don't let an installer bundle a battery into a payback table that claims both savings and resilience at the same time.
- 1. IRS Form 5695 (2025) instructions. Verified 2026-05-16: “You can't claim residential clean energy credits for expenditures made after December 31, 2025.” irs.gov/instructions/i5695 ↩
- 3. EIA Electric Power Monthly, Table 5.6.A — Average Price of Electricity to Ultimate Customers by End-Use Sector. February 2026 residential average: 17.65 ¢/kWh, +7.4% year over year vs February 2025. Released April 23, 2026. eia.gov/electricity/monthly ↩
- 4. U.S. Department of Energy, “Homeowner's Guide to Going Solar.” Lists four consumer-protection red flags: pushy sales tactics, uncertified installers, opaque financing, and reporting paths for bad actors. energy.gov/eere/solar/homeowners-guide-going-solar ↩
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.