gigawatt

Gigawatt (symbol GW) is a unit of power in the International System of Units equal to one billion watts (1,000,000,000 W). It expresses the rate at which energy is produced or consumed. The prefix giga denotes 10^9, and 1 GW is equal to 1,000 megawatts (MW).

In practice, gigawatts are used to describe large-scale electrical capacity. The term is commonly applied to the installed capacity of power plants, hydroelectric facilities, wind and solar farms, and other major generation projects, as well as the capacity of transmission grids and interconnectors. For example, the Three Gorges Dam has an installed capacity of about 22.5 GW, and single large nuclear reactors are often around 1 GW or more. Offshore wind complexes can total several GW.

It is important to distinguish power from energy. Gigawatt measures instantaneous power, while energy is measured in gigawatt-hours (GWh) or terawatt-hours (TWh). If a 1 GW plant operates at full capacity for one hour, it would generate 1 GWh of energy. The actual output depends on capacity factor, downtime, and operating conditions.

Relationship to other units: 1 GW equals 1,000 MW, and the next higher SI prefix is terawatt (TW), equal to 1,000 GW. In energy planning and policy, capacities are discussed in gigawatts, while total energy production over time is discussed in GWh or TWh.