A terawatt-hour (TWh) is a unit of energy equivalent to one trillion watt-hours. It is commonly used to measure large-scale energy production and consumption, such as that from power plants or the total energy used by a country in a year. One TWh can power approximately 90,000 homes for a year, depending on their energy consumption. The term "terawatt" refers to a power level of one trillion watts. In the context of electricity, it helps quantify the output of renewable energy sources like solar power and wind energy, as well as the energy needs of large industries and cities.