Solar energy in the United States already produces enough electricity to power 4.6 million average American homes. Most solar energy is collected at industrial power plants, but residential installations are encouraged by the Solar Investment Tax Credit (ITC), a federal program that subsidizes the cost of new solar installation for homeowners.

Solar energy is expanding quickly, but its effectiveness is geographical. Southwestern states receive more sunlight and can produce more electricity. Here’s a look at the variation in solar production potential using Direct Normal Irradiance (DNI) data from the NREL.

A full-screen version is also available.

Does solar have the potential to offset a significant portion of urban electricity consumption? To find out, we used data from the World Factbook for total electricity consumption and the 2014 US population (318 million) to estimate that the average American consumes about 33 kWh of electricity daily.

To see how much of this electricity demand solar panels could produce, we took 1% of the land area of major US cities as to approximate usable rooftop area and multiplied it with the average DNI for that area to give us a rough estimate of potential daily solar production. We then divided this by the total metropolitan area population multiplied by the average daily per capita electricity consumption of 33 kWh.

The results on the map above are very optimistic, but keep in mind that covering just 1 km2 would require about 500,000 average sized solar panels, and the cost of buying and installing so many solar panels is high. However, since the implementation of the ITC in 2006 the cost of installing solar on a home decreased by 73%, so it is likely that prices will fall even more in the future, and make solar an effective renewable energy solution for cities across the US, expecially those in areas with lots of sunshine.