Solar Score v1 formula
The current calculator starts at 30 points and can add up to 70 more:
- Solar resource: up to 25 points. The annual kWh produced per installed kW is normalized from roughly 1,050 to 1,700 kWh/kW/year.
- Electricity rate: up to 20 points. The retail rate used by the calculator is normalized from roughly 12¢ to 34¢ per kWh.
- Projected payback: up to 25 points. Shorter cumulative payback receives more points, with the strongest contribution around six years and the contribution reaching zero around 16 years.
The result is capped between 30 and 100.
How to read the score
- 80-100: strong planning economics under the assumptions entered.
- 65-79: generally favorable, but price, tariff and roof details still matter.
- 50-64: mixed economics; compare system price and utility rules carefully.
- 30-49: challenging economics under the current assumptions.
These bands are Home Solar Atlas planning labels, not industry certifications.
What Solar Score v1 does not include
We deliberately do not award points for incentives, net metering, export compensation, roof condition or installer quality unless those factors can be represented reliably for the specific home. A generic statewide incentive or an outdated net-metering rule should not make a score look better than the actual project.
As our utility tariff and roof-data layers improve, the score can evolve without hiding the methodology. Version changes will be documented here.
Improve the inputs before trusting the score
Use a ZIP code so production can come from PVWatts, replace the state electricity average with your actual utility rate, and enter a realistic installed $/W from written proposals. Then compare the result with the Quote Analyzer, Payback Calculator and Roof Analyzer.