Great Britain solar hits summer record at 8.8 TWh

In July, the number that mattered arrived as a monthly total: 3.3 TWh of solar electricity, meeting 15% of overall electricity demand. Solar farms and rooftops across Great Britain produced their highest monthly output ever, and across June, July and August they reached 8.8 TWh, a summer record, Carbon Brief’s analysis found.

The record was built on unusually bright weather and a growing fleet. Summer 2026 was the sixth sunniest on record, with more than 620 hours of sunshine, while five heatwaves arrived between May and August. Solar generation rose 23% from the same period in 2025 and was double the level recorded in summer 2021. Chris Hewett, chief executive of trade association Solar Energy UK, attributed the result to clear skies and continued deployment.

Extreme heat did not erase the gain. Solar panels can be affected by high temperatures, but longer daylight hours and higher levels of irradiation more than offset those efficiency losses. Behind that weather effect sits a larger installed base: government figures put UK solar capacity at 21 GW by the third quarter of 2025, while the University of Sheffield says installed capacity is now nearly 24 GW. Domestic rooftop solar represents around 29% of total capacity.

So what changes for people? Nearly 172,000 solar installations were fitted across the UK since the start of 2026, with more than 19,800 rooftop solar panels installed in July alone. Nearly 1.7m households now have solar panels. Across 26 heatwave days, Utility Bidder estimates that households with rooftop solar avoided £86.7m in electricity costs. Hewett said solar and home batteries not only reduced bills for their owners, but also helped keep overall power prices much lower than they would have been with more daytime gas generation.

The record has boundaries. No new half-hourly solar output record was set during summer 2026; that mark remains 15.2 MW, recorded on 23 April 2026. And although the figures are described as UK figures, Carbon Brief notes that the analysis strictly covers Great Britain—England, Scotland and Wales—not Northern Ireland, which belongs to a separate all-Ireland electricity system.