Reading a solar proposal: what to check

A solar proposal can look impressive and still hide the details that decide whether the system is right for you. The numbers are only as good as the assumptions behind them. Here is how to read one like a skeptic.

Start with system size and production

Two figures anchor every proposal:

• System size in kilowatts (kW), the peak capacity of the array.
• Estimated annual production in kilowatt-hours (kWh), how much energy it should make in a year.

Compare that annual production to your actual yearly usage, which you can find on twelve months of utility bills. A system that covers close to your usage is usually the target. One that vastly overproduces may waste money if your utility credits surplus at a low rate. To check the sizing logic yourself, use our guide on how to size a residential solar system.

Interrogate the production estimate

This is where optimistic proposals inflate the appeal. A production number depends on assumptions that are easy to nudge:

• Shading: Was real shade from trees and chimneys modeled, or ignored?
• Orientation and tilt: A south-facing roof produces more than a north-facing one.
• Degradation: Panels lose a little output each year, and a good estimate accounts for it.

Watch the savings math

Many proposals project decades of savings using an assumed utility rate escalator, a yearly percentage that utility prices supposedly rise. A high escalator makes the lifetime savings look enormous. Ask what rate they used and whether it is realistic. Small changes there swing the headline number dramatically.

Confirm the exact equipment

A trustworthy proposal names the specific panel model, inverter model, and quantities, not just "premium panels." Exact models let you:

• Compare two quotes on equal footing.
• Look up the real warranties (product and performance).
• Verify the equipment matches what gets installed.

If you plan storage, confirm the battery model and whether backup is whole-home or partial. Our homeowner guide to battery backup explains that difference.

The fine print that matters

Beyond the big numbers, scan for:

• Warranty terms on panels, inverter, and workmanship.
• What is and is not included, such as electrical panel upgrades or trenching.
• Ownership structure: cash, loan, lease, or power purchase agreement, since each changes who owns the incentives.
• Interconnection and permitting responsibilities.

A vague answer on any of these is a reason to ask more questions before signing.

Remember who has to sign off

No proposal replaces a permitted design. A licensed electrician or PE must design and connect the actual grid-tied system, and your local authority must approve it. Treat the proposal as a plan and a sales document, not a finished engineering package.

The bottom line

Read a solar proposal by checking three things: does the system size match your real usage, are the production assumptions honest, and is the exact equipment listed with its warranties. Question the savings escalator and confirm what is included. Do that and you will separate a solid quote from a shiny one. For more homeowner explainers, browse our guides library.

Educational reference, reviewed 2026-07. A design aid, not a substitute for a licensed electrician or PE. Confirm the enforced NEC edition and local amendments with your AHJ.