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UK Electricity Grid Report 2021

In 2021, Great Britain generated 285 TWh of electricity. Gas was the biggest single source at 37.7%. Renewables (wind, solar and hydro) supplied 27.7%, or 34.4% counting biomass, and each unit generated averaged 183gCO₂ per kWh. Carbon intensity rose 15.3 g on 2020, one of the occasional backwards steps in an otherwise falling series.

Automated summaryIn 2021, Great Britain's electricity grid generated 284.87 TWh, with gas remaining the single largest source at 37.7%, followed by wind at 17.2% and nuclear at 15.2%. Renewables accounted for 27.7% of generation, rising to 34.4% when biomass is included, while low carbon sources made up 49.7% overall, helping to keep average carbon intensity at 183.3 gCO2/kWh. Coal contributed just 1.7%, with the grid running coal-free for 3,471 hours across the year. On the commercial side, the average wholesale price reached £120/MWh, and negative prices occurred for 32.5 hours.

Renewables share

27.7%

34.4% incl. biomass

Low carbon share

49.7%

renewables + nuclear

Carbon intensity

183 g

per kWh · low 34 g, high 331 g

Generation

285 TWh

incl. estimated embedded wind and solar

Coal share

1.7%

3,471 coal-free hours

Peak wind output

14.2 GW

highest half-hour average

The 2021 generation mix, fuel by fuel

share of GB generation
  • Gas37.7% · 107.27 TWh
  • Wind17.2% · 48.97 TWh
  • Nuclear15.2% · 43.42 TWh
  • Imports10.3% · 29.35 TWh
  • Biomass6.7% · 19.02 TWh
  • Solar4.1% · 11.79 TWh
  • Coal1.7% · 4.97 TWh
  • Hydro1.1% · 3.24 TWh
  • Storage0.6% · 1.8 TWh
  • Other0.6% · 1.83 TWh

Wholesale prices in 2021

market index (MID), volume-weighted across APX and N2EX

The average UK wholesale electricity price in 2021 was £120.00 per MWh on the market index (MID) basis. Prices were negative for 32.5 hours across the year. The most expensive half hour came on 9 September 2021 (settlement period 38) at £1983.66 per MWh; the cheapest, £-60.60, came on 30 December 2021.

Average price

£120.00

per MWh, volume-weighted

Highest half hour

£1984

9 September 2021, period 38

Lowest half hour

£-60.60

30 December 2021

Negative price hours

32.5

price below £0/MWh

Electricity supplied, 2009 to 2026

TWh per year, generation basis incl. estimated embedded wind and solar

Britain supplies markedly less electricity than it did in 2009, even as the economy has grown: efficiency, LED lighting and offshored industry all pushed demand down while the mix decarbonised.

How 2021 compares

  • Versus 2020: renewables -3.6 points, carbon intensity +15.3 g.
  • Versus 2009, the first year on record: renewables up 24.3 points (from 3.4%), and each unit of electricity 58.8% cleaner (445 g to 183 g).
  • Explore the neighbouring years: 2020 · 2022 or the full year-by-year table.

Cite this report

You are welcome to reuse the figures on this page with a link back. Suggested citation:

Purely Energy, "UK Electricity Grid Report 2021", purelyenergy.co.uk/grid-report/2021. Derived from NESO historic generation mix data.

2021 grid questions, answered

How green was UK electricity in 2021?

In 2021, wind, solar and hydro supplied 27.7% of GB generation (34.4% including biomass), low-carbon sources supplied 49.7%, and the average carbon intensity was 183 gCO2 per kWh.

What was the biggest source of UK electricity in 2021?

Gas was the largest single source in 2021, supplying 37.7% of GB generation. The full fuel-by-fuel breakdown is on this page.

How much coal did the UK burn for electricity in 2021?

Coal supplied 1.7% of GB generation in 2021 (4.97 TWh), and the grid ran coal-free for 3,471 hours.

What was the average UK wholesale electricity price in 2021?

The average UK wholesale electricity price in 2021 was £120.00 per MWh on the market index (MID) basis, volume-weighted across the year's half-hourly trading.

How many hours were UK power prices negative in 2021?

UK wholesale power prices (market index basis) were negative for 32.5 hours in 2021.

Use the data

Every figure on this page, as a CSV you can drop into a spreadsheet.

Download 2021 data (CSV)

Basis: NESO historic generation mix (GB transmission generation plus estimated embedded wind and solar), aggregated by calendar year, energy-weighted. Renewables is NESO's wind + solar + hydro measure; the biomass-inclusive share is shown alongside. See the live version of this data on our real-time grid map and today's prices on wholesale market data.

Data comes from the Elexon Insights Solution (BMRS), the NESO Data Portal and the Carbon Intensity API, a project by the National Energy System Operator and the University of Oxford Department of Computer Science. Contains BMRS data © Elexon Limited copyright and database right 2026.

Energy decisions for the grid of 2026

The mix above sets the shape of wholesale prices. We turn it into procurement strategy for businesses across the UK, from fixed contracts to flexible purchasing.

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