The formula
Solar cost per watt = solar-only system price ÷ DC system watts.
Example: a $25,000 solar-only cash price for a 10 kW DC system is $2.50/W because 10 kW equals 10,000 watts.
$2.60/W national benchmark
Home Solar Atlas currently uses the EnergySage Marketplace residential solar pricing national reference, updated September 11, 2026, when a state-specific benchmark is not available. Treat it as a comparison point rather than a fair-price verdict for a specific home.
Verify the DC system size before trusting $/W
The denominator matters. If a proposal's quoted DC kW does not reconcile with panel count × module wattage, the resulting $/W comparison can be distorted even when the project price itself is correct.
For a mixed array, add the DC nameplate of each module group before dividing price by watts. Keep inverter AC capacity separate from module DC nameplate.
Use the solar-only cash price
For the most useful comparison, separate items that are not part of the base PV system:
- Home battery storage.
- Roof replacement or structural work.
- Main-panel or service upgrades that are quoted separately.
- EV chargers or unrelated electrical work.
- Loan dealer fees or financing premiums when comparing equipment/install pricing.
You can still evaluate those costs separately; they simply should not distort the solar-only $/W comparison.
Why financed $/W can be misleading
If a lender or installer increases the project price to buy down the interest rate, dividing the financed price by system watts mixes equipment/install cost with financing cost. Ask for the cash price first, then evaluate the loan with the Solar Loan Calculator.
Cost per watt is not the whole decision
A lower $/W proposal can still use a different roof layout, equipment package, production assumption or workmanship coverage. Compare $/W together with expected production, roof fit, warranty details and financing terms.