Solar thermal energy (or STE) is a technology for harnessing solar energy for heat. Solar thermal collectors are characterize by the US Energy Information Agency as low, medium, or high temperature collectors. Low temperature collectors are flat plates generally used to heat swimming pools. Medium-temperature collectors are also usually flat plates but are used for creating hot water for residential and commercial use. High temperature collectors concentrate sunlight using mirrors or lenses and are generally used for electric power production. This is different from solar photovoltaics, which convert solar energy directly into electricity.