How to Compare Solar Quotes: The Only 5 Numbers That Matter

Most solar installers know that homeowners find it hard to compare quotes. That is why they lead with monthly payment figures ("only $89/month!") rather than the numbers that actually determine value. Here are the five figures you need from every quote before you can compare them properly.

Number one: price per watt (gross). Divide the total pre-incentive system cost by the system size in watts. A $28,000 quote for 8 kW is $3.50/W. A $24,000 quote for 8 kW is $3.00/W. This is the only fair apples-to-apples comparison across different system sizes, and it tells you immediately whether you are in the market range. Use our Quote Checker to compare against your state median.

Number two: estimated annual production in kWh. Every reputable installer should provide this from software like Aurora Solar or Helioscope. This is more important than system size alone — a shaded 10 kW system may produce less than a well-sited 8 kW system. If a quote does not include a production estimate, ask for one.

Number three: cost per estimated annual kWh produced. Divide the gross system cost by the estimated annual kWh. This normalizes for production differences: $28,000 producing 9,000 kWh/year is $3.11 per annual kWh. $24,000 producing 10,500 kWh/year is $2.29. The lower number is a dramatically better deal even though the gross price is higher.

Number four: panel and inverter model, not just brand. "SunPower panels" is not enough — there are 10+ SunPower models with different efficiencies and warranties. Get the exact model number, wattage, efficiency, and warranty terms for both panels and inverter. Premium panels carry a premium price; make sure you know what you are paying for.

Number five: warranty terms. The industry minimum is a 25-year production warranty from the panel manufacturer and a 10-year workmanship warranty from the installer. Better installers offer 25-year workmanship warranties. The inverter manufacturer typically warrants 10 to 25 years depending on type. Ask specifically what happens if the installer goes out of business during the warranty period.