Peak sun hours by city

Peak sun hours (PSH) is the number of full-strength sunlight hours a square metre collects in a day. It is the single input that decides how many panels you need. These are measured values, from NASA POWER daily reanalysis for 2024, for 35 cities.

Peak sun hours table

City	State	Peak sun hours/day	Annual irradiance (kWh/m²)
Austin	Texas	4.83	1,763
Atlanta	Georgia	4.63	1,692
Baltimore	Maryland	4.13	1,508
Boston	Massachusetts	3.87	1,412
Charlotte	North Carolina	4.50	1,644
Chicago	Illinois	4.11	1,500
Cleveland	Ohio	3.76	1,372
Dallas	Texas	4.74	1,730
Denver	Colorado	4.97	1,816
Detroit	Michigan	3.86	1,408
Houston	Texas	4.54	1,656
Indianapolis	Indiana	4.15	1,515
Jacksonville	Florida	4.81	1,754
Kansas City	Missouri	4.45	1,625
Las Vegas	Nevada	5.53	2,018
Los Angeles	California	5.55	2,025
Louisville	Kentucky	4.17	1,523
Memphis	Tennessee	4.46	1,629
Miami	Florida	4.93	1,798
Milwaukee	Wisconsin	3.81	1,391
Minneapolis	Minnesota	3.85	1,405
Nashville	Tennessee	4.31	1,573
New Orleans	Louisiana	4.59	1,677
New York	New York	4.01	1,463
Phoenix	Arizona	5.84	2,130
Pittsburgh	Pennsylvania	3.91	1,428
Portland	Oregon	3.77	1,374
Raleigh	North Carolina	4.52	1,650
Richmond	Virginia	4.29	1,566
San Antonio	Texas	4.83	1,762
San Diego	California	4.88	1,782
San Francisco	California	4.89	1,783
Seattle	Washington	3.48	1,270
St Louis	Missouri	4.33	1,581
Tampa	Florida	5.22	1,906

What peak sun hours means

PSH converts a location's sunlight into the equivalent number of hours at 1,000 W/m². A city at 4.0 PSH collects about 20% less energy per panel than a city at 5.0 PSH over a year. Multiply PSH by panel wattage to get the panel's real daily output before losses.

We report the annual figure as annual irradiance ÷ 365, which is the standard definition and is the number used in the solar panel calculator.