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Rankings · Weather
Average daily solar energy.
Global horizontal irradiance: the solar energy reaching a horizontal surface, in kilowatt-hours per square metre per day, averaged over years. It is a measurement rather than a description, and it is used here because sunny days are not published for every county while this is. It tracks cloud cover closely, so it answers how grey a place is — the Olympic Peninsula and Arizona sit at opposite ends. It also indicates what a rooftop solar array would produce. Modelled from satellite cloud observations at roughly four kilometres, then read at the county's population-weighted centre, so a large county with varied terrain is represented by where its people live rather than by its average.
Arizona has the highest published solar in this comparison, at 5.76 kWh/m². The next states shown are Hawaii (5.66 kWh/m²) and New Mexico (5.56 kWh/m²).
The table orders 50 states by average daily solar energy. It describes one published measure, not an overall judgment about where to live.
Use the result as a starting point, then compare the underlying source, dates, and local county figures before making a decision. Global horizontal irradiance: the solar energy reaching a horizontal surface, in kilowatt-hours per square metre per day, averaged over years. It is a measurement rather than a description, and it is used here because sunny days are not published for every county while this is. It tracks cloud cover closely, so it answers how grey a place is — the Olympic Peninsula and Arizona sit at opposite ends. It also indicates what a rooftop solar array would produce. Modelled from satellite cloud observations at roughly four kilometres, then read at the county's population-weighted centre, so a large county with varied terrain is represented by where its people live rather than by its average.
Not ranked, because this measure is not published for them: Alaska. Needs a county population-weighted centre.
These guides combine this measure with other clearly named inputs; they are not overall state verdicts.
Free to use. The chart names its source and links back, so it stays honest wherever it ends up.
<iframe src="https://movermath.com/embed/solar" width="100%" height="420" style="border:0" loading="lazy" title="Average daily solar energy by state"></iframe>Source: NREL National Solar Radiation Database. · How this is built