Methodology

How the figures on SunYieldMap are produced, and what they leave out.

Model

Solar output modeled with the PVWatts® Calculator API v8 from the National Laboratory of the Rockies (NLR, formerly NREL), using NSRDB typical-meteorological-year weather data. PVWatts® is a registered trademark of the Alliance for Energy Innovation, LLC. This site is independent and is not endorsed by NLR, the Alliance or the U.S. Department of Energy.

Reference system

The reference system behind every headline figure.

1 kW (DC) of standard modules, fixed roof mount, 14% system losses, south-facing (azimuth 180°) at a 20° tilt. Comparison runs: flat (0°), tilt equal to latitude, east (90°) and west (270°) at 20°, and a 1-axis tracker. A 6 kW figure is the 1 kW result × 6.

Weather

Typical meteorological year (TMY) data from the National Solar Radiation Database, from the grid cell nearest each city. TMY represents a typical year, not any particular year, so output in a given year can be higher or lower.

Cities

City locations and populations: U.S. Census Bureau (2024 Gazetteer, 2024 cartographic boundaries, Vintage 2024 population estimates). The largest place in each state and DC, then the next-largest places nationally, to 100 cities. State figures are averages of the listed cities only.

Limits

These are model estimates for an unshaded roof. Real output depends on shading, roof direction and pitch, equipment, soiling and snow. SunYieldMap reports energy output only.