How to compare solar quotes per watt
A step-by-step way to put solar quotes on the same footing: the per-watt calculation, a worked example, and the questions that stop apples-to-oranges comparisons.
Solar quotes arrive in different shapes: a total price, a monthly payment, a loan, a lease. To compare installers you need a common yardstick. The most useful one is the price per watt of installed capacity. This guide shows how to calculate it, how to read it, and what else to compare. It is general information, not advice.
Step 1: Calculate price per watt
Take the total price before any incentives and divide by the system's size in watts. A 7 kW system is 7,000 watts. In this illustrative example, a quote of $24,500 gives $24,500 divided by 7,000, or $3.50 per watt. Use the DC rating of the panels (sometimes shown as "kW DC" or "panel capacity"), not the inverter's AC rating, because the two differ. If a quote lists only panel count, multiply the number of panels by each panel's wattage: 18 panels of 400 W is 7,200 W.
Step 2: Put every quote on the same basis
- Before or after incentives. Compare gross prices to gross prices. Incentive rules change over time and depend on your tax situation, so do not mix net and gross. The IRS says on its residential clean energy credit page that the credit is not available for property placed in service after December 31, 2025; check the current rules before counting on any federal incentive.
- Cash, loan and lease. A loan may include financing charges in the price; a lease or power purchase agreement has no purchase price at all. Ask for the cash price in every case.
- Scope. Does the price include permits, interconnection, monitoring, roof work or an electrical panel upgrade? Does it include a battery? Ask for the solar-only price too.
- Equipment. Panel efficiency, brand, microinverters versus a string inverter with optimizers, and warranty length all vary.
Step 3: Adjust for size
Many costs are fixed per job, so larger systems usually cost less per watt. Compare systems of similar size. A worked illustration with made-up numbers: quote A is $21,000 for 6,000 W ($3.50 per watt); quote B is $30,800 for 11,000 W ($2.80 per watt). Quote B looks cheaper per watt, but the systems are not the same size, and you may not need 11,000 W. Ask each installer to price the same size, or to explain the difference.
A second caution: the cheapest option per watt can also be the one that leaves out something you need. If quote B excludes a panel upgrade that quote A includes, add an estimate for it before you compare. Ask each installer in writing what is excluded, and what the likely extra charges are if the roof or panel turns out to need work.
Step 4: Look at expected production
Price per watt says nothing about how much electricity you will get. Ask for a production estimate in kWh per year, with the assumptions: roof direction and tilt, shading, and panel degradation. As an illustration, if one design gives 9,000 kWh a year for $24,000 and another gives 8,000 kWh for $22,000, the cost per yearly kWh is $2.67 and $2.75, so the lower price is not the better deal. Treat any such estimate as an estimate: ask what degradation rate and shading loss were assumed, and compare designs using the same assumptions. The National Renewable Energy Laboratory's PVWatts calculator, which the DOE homeowner's guide points to, lets you check an estimate yourself.
Step 5: Use this site's numbers
Each profile shows the installer's median price per watt in the data, the range of the middle half of its installs, and the state's median for the same years. If your quote is far outside the range, ask why. There may be good reasons, such as a steep roof, a battery or premium panels, or none. The data ends in 2023, so allow for changes in equipment, labor and policy since then. See how to read the Tracking the Sun data for what the numbers do and do not mean.
Step 6: Compare beyond price
Price and production are only part of the decision. The questions below cover the rest, and the answers should be in the contract, not just in the sales conversation.
- Is the company licensed in your state, and does it carry insurance?
- Does the installer use employees or subcontractors?
- What are the workmanship and equipment warranties, and who stands behind them if the company closes?
- How long do permits and utility interconnection usually take?
- What does the contract say about price changes, the payment schedule and cancellation?
A comparison table to copy
For each quote, write down: total price; DC watts; price per watt; battery included (yes or no); panel and inverter models; estimated kWh per year; workmanship warranty in years; payment schedule; financing total cost. Seeing three columns side by side often shows where one quote is quietly leaving something out.
Add a row for the date and the price validity period, since equipment and tariff costs change and some quotes expire. Add another for who does the work: the company's own crew or a subcontractor. If an installer will not itemize, treat that as a data point in itself.
Get at least three quotes
Ask each installer for an itemized quote and a design that shows the panel layout and expected production. Do not let a deadline stop you comparing. Then run through how to check a solar installer and read what affects the price of home solar to understand any differences.
General information only, current as of the date above. The information on Solar Price Atlas is not a recommendation or a guarantee of anyone's work. A license record shows registration status on the date shown, not workmanship, insurance coverage at the time of your job, or suitability for your project. Confirm license, insurance and permits directly before you hire. Rules and programs change; check the official sources linked in this guide.