Solar energy can be used almost anywhere to power a home, generate electricity or run small appliances like roadside signs or even calculators. The . Department of Energy's Solar Energy Potential Map shows that every location in the continental United States offers enough sunlight to generate at least 250 watts of electricity per square foot of collector space per day, with many locations capable of generating much more than that. Hydropower production, on the other hand, is limited to locations with access to a sufficient supply of running water to power turbines and other generating equipment. Many areas in the United States are considered exclusion areas, where federal or other statutes prohibit the use of hydropower production.