A gigawatt (GW) is a unit of power equal to one billion watts or one million kilowatts. It measures the rate at which energy is generated, consumed, or transferred, and is commonly used when discussing large-scale electricity systems. Producing or consuming power at a rate of one gigawatt for one hour equals one gigawatt-hour (GWh) of energy.
To put this into perspective, a continuous power output of one gigawatt could, in theory, supply electricity to roughly 700,000 to 900,000 average U.S. homes for a year. This estimate assumes typical household energy use of about 10,000 kilowatt-hours annually and a power plant operating continuously for all 8,760 hours in a year. In practice, efficiency losses, fluctuations in demand, and maintenance downtime mean the actual number of homes served would be lower.
Some of the world's largest power plants operate at the gigawatt scale or higher. The Three Gorges Dam in China, a hydroelectric facility, leads with a capacity of about 22.5 gigawatts. It is followed by the Itaipu Dam (Brazil/Paraguay) at around 14 gigawatts, and the Grand Coulee Dam in Washington State, U.S., at roughly seven gigawatts.
Among nuclear power facilities, Japan's Kashiwazaki-Kariwa Nuclear Power Plant once had the highest installed capacity at 7.96 gigawatts, although it has remained offline since 2011 due to safety concerns following the Fukushima disaster. Other major nuclear sites include South Korea's Hanul plant (7.3 gigawatts) and Canada's Bruce plant (6.2 to 6.6 gigawatts). In Europe, Ukraine's Zaporizhzhia plant has a net capacity of 5.7 gigawatts, although its operation has been suspended since 2022 due to armed conflict in the region.
Gigawatt-scale renewable energy installations are also becoming commonplace. Massive facilities such as Bhadla in India and Golmud in China each generate around two to three gigawatts, demonstrating how rapidly solar power has expanded to a scale once reserved for fossil fuel and nuclear plants.
As of early 2026, the world's total electricity generation capacity stands at roughly 10,000 gigawatts. Renewable energy now represents a substantial share of this capacity, adding hundreds of gigawatts annually as solar and wind technologies continue to become more cost-effective. Asia, and particularly China, leads this growth, contributing more than half of all new capacity through a combination of government incentives and industrial expansion.
Although there is no inherent limit to the total gigawatt capacity the planet can support, growth is naturally constrained by technological capabilities, resource availability, environmental effects and global demand. These constraints include land use limitations, materials availability for solar panels and wind turbines, grid expansion challenges, and even secondary climate effects such as waste heat.