The United Kingdom has a National Grid that covers most of mainland Great Britain and several of the surrounding islands, as well as some connectivity to other countries. The electrical sector supplies power at 50 Hz AC, and ~240 volts is supplied to consumers. In 2020 the electricity sector's grid supply came from 55% low-carbon power (including 24.8% from wind, 17.2% nuclear power, 4.4% solar, 1.6% hydroelectricity, 6.5% biomass), 36.1% fossil fuelled power (almost all from natural gas), and 8.4% imports. Renewable power is showing strong growth, while fossil fuel generator use in general and coal use in particular is shrinking, with historically dominant coal generators now mainly being run in winter due to pollution and costs, and contributed just 1.6% of the supply in 2020.