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State of the grid: September 2026

Britain's electricity in September 2026, built from public data and filled in by code.

Great Britain's electricity averaged 108 grams of CO₂ per kWh in September 2026, 4% lower than in September 2025 (112 g/kWh).

Published 8 October 2026. Every sentence is filled in by code from public data; no figure is typed by hand.

Average carbon intensity
108 g/kWh
112 g/kWh a year earlier
Zero-carbon share
60%
56% a year earlier, without hydro (no data)
Balancing costs
£505m
£479m on constraints
Agile, London
26.2p
131 half hours below zero

Wind supplied 38% of electricity, ahead of gas at 21% and nuclear at 13%. Zero-carbon sources (wind, solar, nuclear and hydro) made up 60%, and wind's share peaked at 72.8% at 04:30 on Saturday 19 September.

Wind supplied the most power, 38%

Average share of generation in September 2026. The tick marks a year earlier. No tick for hydro: the source has a gap for September 2025.

  • Wind38%, 39% a year earlier
  • Gas21%, 24% a year earlier
  • Nuclear13%, 11% a year earlier
  • Imports8%, 11% a year earlier
  • Biomass9%, 8% a year earlier
  • Solar7%, 7% a year earlier
  • Hydro2%

Scale: 0 to 50%.

The cleanest day was Saturday 19 September (60 g/kWh) and the dirtiest Tuesday 22 September (190 g/kWh). The cleanest single half-hour, 27 g/kWh, was at 14:00 on Saturday 12 September.

Intensity was below 100 g/kWh in 50% of half-hours (48% a year earlier).

The cleanest day was Saturday 19 September, at 60 g/kWh

Every half hour, coloured by the Carbon Intensity API's national band.

Tap or point at a half hour to read it.

avgT 195W 2145T 373F 471S 580S 669M 783T 884W 9107T 10113F 11129S 1281S 13164M 14151T 1578W 16112T 1766F 1861S 1960S 2081M 21162T 22190W 23130T 24134F 25142S 26112S 2783M 28180T 29101W 30105
  • Very low
  • Low
  • Moderate
  • High
  • Very high

Balancing the grid cost NESO £505 million. Of that, £479 million (95%) went on constraints, mostly paying generators to change output when power lines were full (£466 million), and 1,772 GWh of generation was turned down because the network could not carry it.

On Agile Octopus in London, the unit price averaged 26.2p/kWh and ranged from −5.0p to 86.7p. Prices were below zero in 131 half-hours, when customers were paid to use electricity.