GWh meaning

GWh describes a quantity of electrical energy used, generated or contracted over a period in energy and infrastructure matters (for example in power purchase agreements, generation forecasts and regulatory reporting). It is a descriptive metric unit rather than a term defined by case law, but it is widely used across UK and Irish legislation, licences and market codes that adopt SI units. One gigawatt hour equals one billion watt-hours, 1,000 megawatt hours (MWh) or 1,000,000 kilowatt hours (kWh). It measures energy (work done), not capacity; do not confuse GWh with GW (gigawatts), which measure instantaneous power. Legal practitioners encounter GWh when specifying contracted delivery or offtake volumes in PPAs and supply agreements, when aggregating metered settlement data, in Statements of Need and environmental assessments, and in reporting generation or consumption (including for CfD settlements, REGOs/Guarantees of Origin and emissions calculations, typically recorded per MWh but often aggregated to GWh). Usage and meaning are consistent across England and Wales, Scotland, Northern Ireland and Ireland, including within the Single Electricity Market. Metering and settlement frameworks (e.g. Ofgem/Elexon in Great Britain and the SEM in Ireland/Northern Ireland) express interval data in kWh/MWh and commonly report annual or project-level totals in GWh.