Sunlight can be used as energy directly as heat or light, or by converting it to mechanical energy or electricity.¹ In one process, called solar thermal energy, the heat of the sun is used to power a steam or gas turbine. In another process, solar cells absorb sunlight and create an electrical current.² In the 1950s, research teams at Bell Labs developed silicon photovoltaic cells, which replaced earlier cells made from selenium, improving their efficiency, especially as the cost of photovoltaic (PV) cells decreased.³ PV power makes up more than 95% of the solar power market.⁴

The solar power industry saw an increased demand in the 1970s due to the oil embargo.⁵ Solar power has continued to increase with more tax incentives and pro-solar power policies, coupled with a decreasing cost of equipment.⁶ According to the Energy Information Administration, solar accounts for about two percent of electricity generating capacity in the United States.⁷ This growth is happening in both utility-scale solar power (power plants that have at least one megawatt of total electricity generating capacity), and small scale solar power systems, also known as distributed solar electricity, which is solar electricity generated at residential, commercial or industrial locations and not connected to a power plant.⁸