Guide
What a solar quote must show before you can judge it
The lines that belong on any solar proposal, the assumptions that quietly decide the payback, and the questions that produce real answers.
Updated September 18, 20262 min readAwaiting expert review
Written from primary sources by our editorial team. A credentialed reviewer hasn't signed off yet, so this page isn't in search results. It's information, not professional advice.
Not sure where to start? Take the Solar Check.About 2 minutes. Rough answers are fine.Solar proposals are long and often beautifully designed, which is not the same as being comparable. Here is what has to be in one before you can judge it against another.
The lines
The Department of Energy's homeowner guide is a good checklist to read alongside any proposal. System size in kW DC. Price per watt. Panel make, model and wattage. Inverter type, make and model. Estimated annual production in kWh. The shading loss assumed. Roof penetration warranty and its term. Workmanship warranty and its term. Any written production commitment. Whether a main panel upgrade is included. Permit and interconnection costs. And if financed, APR, term, total paid, and the dealer fee.
The assumptions that decide the answer
A payback figure is only as good as what went into it. Three inputs do most of the work:
Production. Check it against NREL's PVWatts for your own address. If the proposal is materially higher, ask what shading loss was assumed.
Escalation. How fast electricity prices are assumed to rise. It compounds over twenty-five years and it is the easiest lever to make a weak deal look strong.
Any federal credit. If it appears at all, the proposal is out of date — see what happened to the federal solar credit.
Questions worth asking every installer
What is the price per watt? What annual kWh are you putting in writing, and what happens if it underperforms? What shading loss did you assume? Who warrants the roof penetrations and for how long? Is any federal credit assumed anywhere in this proposal? If financed, what is the dealer fee as a dollar number?
Bottom line
Get size, price per watt, production and assumptions on every proposal, then compare. The cost context is in what solar costs to install.
Common questions
What must be on a solar quote?
System size in kW, price per watt, panel and inverter make and model, an annual production figure in kWh, the assumptions behind the payback, and the full financing terms if financed.
Which assumption matters most?
The electricity price escalation rate, because it compounds over twenty-five years and can make a poor payback look good.
What is a production commitment?
A written undertaking that the system will produce a stated minimum output, with compensation if it does not. Terms vary a great deal and some proposals have none at all.
Should I accept a quote that only shows a monthly payment?
No. Ask for the cash price and the price per watt. A monthly figure alone hides both the system price and the finance cost.
Sources
- NREL Developer Network: PVWatts v8 API documentation
- IRS: Residential Clean Energy Credit — not available for property placed in service after 31 December 2025
- FTC consumer advice: How to avoid a home improvement scam
- U.S. Department of Energy: Homeowner's guide to going solar
- CFPB: report on solar lending
By SolarRealCost Editorial Team. First published September 18, 2026. Advertiser disclosure
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