Our data & methodology
SunWorth estimates residential solar economics for every U.S. county from free government data. We are an independent estimator — not an installer, lender or government agency.
Where the numbers come from
- Production — annual kWh for a reference system is modeled with NREL PVWatts v8 using each county's location and typical-meteorological-year weather.
- Electricity rate — residential $/kWh from NREL Utility Rates v3, falling back to the EIA state average when a local rate is unavailable.
- Federal tax credit — the 30% Investment Tax Credit (ITC), constant through 2032 under current law.
The model
We size a 6 kW reference system at a national-average installed cost of $3.00/W ($18,000 gross, ~$12,600 after the ITC). Annual savings are production × your local rate; payback is net cost ÷ annual savings; 25-year savings apply a 3%/yr utility-rate escalation. The interactive calculator re-sizes the system to your actual bill, shading and roof orientation.
The Solar Value rating
Each location gets a Solar Value rating from its payback period: Excellent (< 7 years), Good (7–10), Fair (10–14) and Low (> 14). A "Low" rating doesn't mean solar can't work — it means it's a longer-term play.