A gigawatt-hour (GWh) is a unit of energy that represents one billion watt-hours. It is commonly used to measure large amounts of electricity generated or consumed over time. For example, if a power plant produces one gigawatt of power continuously for one hour, it generates one gigawatt-hour of energy. This measurement is important in the energy industry, as it helps quantify electricity production from sources like solar panels, wind turbines, and nuclear power plants. Understanding gigawatt-hours allows for better planning and management of energy resources to meet the demands of homes and businesses.