Data sources and methods

Dataset built/refreshed: 2026-10-21. Annual EIA data through 2025; monthly EIA data through 2026-07. Berkeley Lab installation year: 2025 (Berkeley Lab, U.S. Distributed Solar and Storage: 2026 Data Update (August 2026); prices in 2025 dollars). Coverage: 51 state/DC records and 347 cities. Solar source: PVGIS-ERA5 (EU JRC) fallback.

The build date is the dataset snapshot date; separate retrieval dates for each source are not supplied.

Sources

• Electricity prices, sales, revenue and customer counts: U.S. Energy Information Administration retail sales API. Monthly prices were checked against Electric Power Monthly.
• Residential installed solar prices and median installed size: Berkeley Lab, Tracking the Sun, data files of the report U.S. Distributed Solar and Storage: 2026 Data Update (August 2026), using the installation year shown above. Figures are for host-owned, stand-alone residential PV systems (cash and loan purchases; leases and PPAs excluded). Prices are self-reported and medians describe the participating sample, not a quote for your home. Dollar-per-watt prices are in 2025 dollars (Berkeley Lab adjusts for inflation), before incentives. Where a state median is unavailable, the national median is used. Each page reports its price sample size.
• Solar production: European Commission Joint Research Centre PVGIS, PVGIS-ERA5, fixed rack facing south, 20-degree tilt and 14% system loss. City coordinates represent a place, not an individual roof.
• City selection and coordinates: U.S. Census Bureau population estimates, Vintage 2024, and Gazetteer places. The list includes large Census places and the largest place in each state.

Formulas

Average monthly use = annual residential sales in kWh divided by residential customers and then by 12. Average monthly bill = annual residential revenue in dollars divided by residential customers and then by 12; it includes billed charges.

For solar valuation, the state rate is the arithmetic mean of the trailing monthly residential prices. This differs from the annual price used for rankings. System size in kW = annual average household use divided by local annual kWh per kW. Gross cost = system size × 1,000 × installed dollars per watt. Annual production = size × local yield. Annual value = production × state dollars per kWh. Simple payback years = gross cost divided by annual value. Displayed values are rounded; recomputing with rounded inputs can differ.

State solar examples use the reference city named on the page; city examples use that city’s yield and state household usage. The calculator permits your usage, price, incentives and export assumptions. It subtracts upfront incentives from gross cost and values exported output at the percentage of retail entered by you.

Limits

State prices are averages, not a city’s or utility’s tariff. Actual bills depend on fixed charges, usage, utility and rate structure. Solar estimates value all output at retail unless adjusted in the calculator; export payments may be lower. Simple payback excludes financing, maintenance, equipment replacement, degradation, escalation and the time value of money. These are estimates, not guarantees.

PVGIS is the current fallback production model, rather than PVWatts. Their weather datasets and modeling assumptions differ, so their outputs are not interchangeable. Shading, roof orientation and installation quality can change actual production.

The federal residential clean energy credit under section 25D ended for systems installed after Dec 31 2025; see the IRS energy credit guidance. State and utility incentives are excluded from published page estimates. Check eligibility and current terms directly before making a purchase.

Missing history values are labeled N/A. Data can be revised or contain errors. Report an issue.