When you run a visualization of solar installations in the U.S. since 2000, two areas stand out. There's the corridor between San Diego and San Francisco, which flashes continually. Then there's a big blob in the North-East, from Maryland to upstate New York. States like Arizona come on-board in the mid-2000s, while much of the rest looks barren by comparison.
One Block Off the Grid, which links up homeowners with solar installers, wanted to know the places in the US with the most solar, and it turned to the National Renewable Energy Laboratory, which keeps a running database called the Open PV Project. To get a a per capita view, NREL divided the number of installs by that place's population.
Fresno scores highest with 182.92
megawatts per person--which 1BOG puts down to the city's relatively small population and several nearby utility-sized projects. Phoenix, Las Vegas and Sacramento come next. They owe their top positions to nearby deserts, which again are ideal for bigger projects. San Francisco is in fifth place, mainly because of high electricity prices (which encourages homeowners to switch from the grid) and several big solar companies based in the city.
It's a similar story in Massachusetts--Boston ranks eighth. New York, and New Jersey, which also have a large number of residential installations (New Jersey is the third state in the nation, with 18,348 overall). NREL's data captures about two-thirds of panels and doesn't divide up commercial from residential. But 1BOG believes the two markets broadly mirror one another.
Check out NREL's Market Mapper for more data, including a break-down by county. It looks like Los Angeles county has the single most number of installs (19,558), giving it a similar number to Arizona (20,930).