The overwhelming majority of the United States gets enough sunlight to make a PV system viable—an average of nearly 5.0 kilowatt hours per square meter daily (kWh/m2/day). But there’s a wide swath of the southwest that looks like a giant fireball on the National Renewable Energy Laboratory’s (NREL’s) map, “Photovoltaic Solar Resources of the United States.” This region gets 6.8 kWh/m2/day or more of solar radiation.

In many of these areas PV is quickly gaining traction and some of the larger cities in the region are capitalizing on it, but other cities could stand to catch up. Local and state incentives can help home and business owners install solar on their home. Since solar installers can add arrays quickly, the leaders are fluid at best.

San Diego, Calif, is an ideal market for PV and the city is capitalizing on it. The city is one of the DOE’s Solar America Cities, and the goal of its “Sustainable Energy 2050 Plan” is to create a local, reliable, and independent energy system that serves as a blueprint for the nation.

San Francisco’s ties to silicon valley have made it a solar leader for a long time. As early as 2001, the city approved a $100 million bond initiative for renewables, Solar Cities America said. The city passed a renewable energy initiative under which 31 MW of PV will be operation by 2012.

Tucson, Ariz. gets some of the nation’s best sunlight. While Tucson is part of the Solar Cities America program, it’s ripe for more solar development. Indeed, the program notes that the Tucson Solar Initiative is now focused on working “to overcome the market barriers of high up-front cost and low levels of awareness.”

Flagstaff, Ariz. has 288 days of sunshine a year, but NREL’s OpenPV project said that at this point it has only 246 kilowatts of PV installed.

Pueblo, Colo. in southern part of the state, has about 330 days of sun a year but only has about 6 kilowatts of PV installed, OpenPV shows. That low number may change soon. The city’s constructing a new PV-powered waste-water plant. And its economy is being revitalized with a Vestas wind-turbine manufacturing plant.