TWh, GWh and MWh

TWh (terawatt hour), GWh (gigawatt hour) and MWh (megawatt hour) all measure the same thing, electrical energy, at different scales: 1 TWh equals 1,000 GWh, and 1 GWh equals 1,000 MWh. World Power Monitor uses TWh for a whole country's annual generation, GWh for smaller countries or shorter periods, and MWh for hourly or daily grid operator figures, always converting rather than mixing units within one figure.