How to Read a Solar Quote: What to Check Before You Sign

A solar proposal contains eight to twelve line items that most homeowners skip. Three of them are the ones that get people into trouble.

What every solar quote should include, what common omissions mean, and the three assumptions that make the biggest difference in whether the payback is real.

Key takeaways

A solar quote should clearly state system size in kW-DC, panel and inverter manufacturer and model, estimated annual production in kWh, gross price, itemized federal ITC calculation, and production guarantee.

If any of those are missing, ask for them explicitly before comparing proposals from different installers.

The three inputs that most change payback math are the production estimate, the electricity rate assumed, and the net price after any financing dealer fees.

A solar quote should clearly state system size in kW-DC, panel and inverter manufacturer and model, estimated annual production in kWh, gross price, itemized federal ITC calculation, and production guarantee.

If any of those are missing, ask for them explicitly before comparing proposals from different installers.

The three inputs that most change payback math are the production estimate, the electricity rate assumed, and the net price after any financing dealer fees.

Three numbers decide most of the payback argument

Most solar disputes and buyer regrets trace back to three numbers: estimated annual production (kWh), effective electricity rate used in savings calculations, and the net price after credits and dealer fees.

Everything else in a quote ??panel brand, inverter type, warranty length ??matters less than whether these three are accurate and verifiable.

What a complete solar quote should include

A professional solar proposal should answer every one of these questions without you having to ask.

The production estimate is where most quotes go optimistic

Installers generate production estimates from software like PVWatts, Aurora, or Helioscope. The accuracy depends heavily on how shade is modeled. A tree that blocks 15% of production in July looks different in satellite imagery versus an on-site shade analysis.

Run the installer's estimated annual production through PVWatts yourself: enter your address, system size, and the same losses figure (typically 10??4%). If the installer's number is more than 10% above PVWatts output at default settings, ask why.

Verify the electricity rate assumption

Solar proposals calculate savings using an assumed electricity rate. If that rate is your current bill average rather than your marginal rate (the rate on the next kWh you would have used), the savings figure overstates the value.

Many bills have tiered pricing: the first 400??00 kWh is cheaper, the next block is more expensive. Solar offsets your most expensive consumption first. That can mean your effective rate for solar savings purposes is higher than your average rate ??but only by a controlled amount.

Check what rate the proposal uses. If it shows 'annual rate escalation of 3.5%', that assumption is driving a significant portion of 25-year savings. A 2% escalation instead of 3.5% can shift the 25-year net savings by 20??0%.

Net price: what you actually pay

The gross price minus the federal ITC is the net cost your payback must recover. For a financed system, the net cost also includes interest ??a $21,000 loan at 6.99% over 20 years costs about $19,000 in interest, nearly doubling the net cost of a $30,000 system.

Ask every installer for: gross price, cash price, financed price (if relevant), and what dealer fee is built in to the financed price. Comparing only the 'net cost after ITC' on financed proposals misses the financing cost layer.