The potential resource base for PV in the United States is enormous; however, there are a number of challenges related to realizing this potential including relatively high cost, intermittent output, and potentially significant land use. The costs of PV have been declining significantly during the past couple of decades, and there are strong prospects for further declines in cost during the next decade. The issue of intermittency can be addressed through a number of potential means, and will likely become increasingly important as market penetration increases beyond a few percent of electricity consumption. The issue of land use is often cited as an important issue for renewable energy technologies. Determining the land requirements of solar PV at high penetration helps evaluate its potential to reduce both the carbon emissions and the “Ecological Footprint” associated with electricity generation and use.