UK Solar Hits Quarterly Record But Wind Curtailment Drags Renewables Share Below 2024 Peak
Montel data show wind losses during June's heatwave cut the UK's renewable share to 44%, below last year's 50.5%, as curtailment emerges as a systemic market feature.
Britain broke a quarterly solar generation record this summer, yet renewables' overall share of UK electricity fell short of last year's levels. Wind, solar, hydro and biomass together produced over 127 TWh across the period, Montel reported, amounting to roughly 44% of the country's electricity supply — down from the 50.5% share recorded in 2024.4
June was the hottest month since records began, and it delivered exactly the trade-off the GB market is learning to price. Solar output climbed to a quarterly record. Wind generation fell, hit by curtailment during the heatwave. A grid that sources nearly half its electricity from weather-dependent generation pays for that dependence in both directions.4
Montel's analysis frames commercial curtailment as a market feature of the GB system, not a temporary friction. The government's clean power 2030 plan, published in December 2024, targets offshore wind capacity of 43 to 50 GW, onshore wind of 27 to 29 GW, and solar of 45 to 47 GW — effectively tripling renewable generation from current levels.1 Curtailment costs are already visible. Scaling capacity without equivalent investment in the grid infrastructure to absorb it points in one direction.1
Globally, solar and wind together produced about 5,525 TWh in 2025, representing 17.2% of all electricity generated worldwide, up 8.2% on the previous year, according to Oilprice.com.5 China led with 1,128 TWh of solar alone, nearly 42% of the world total, while the US came second at 469 TWh. Germany generated 134 TWh, followed by Brazil at 116 TWh and India at 104 TWh.5 The UK's 127 TWh across all renewables sits in that context — significant for a mid-sized European economy, but generated against a grid infrastructure that is straining to keep pace.
The government's response on the storage side centres on pumped hydro. Britain currently has almost 1,700 hydropower schemes with an installed capacity of around 2 GW, according to Oilprice.com. By 2025, eleven pumped-storage hydro projects were under development across the UK, with an expected combined storage capacity exceeding 10 GW and 200 GWh — equivalent to about 25% of the country's power demand once completed.3
The economic case is there in the modelling. A study from Imperial College London found that just 4.5 GW of new pumped-storage hydro with 90 GWh of storage could save up to £690 million a year in energy system costs by 2050.3 Negative pricing events, which curtailment both produces and exacerbates, are precisely the cost the storage capacity is meant to offset. The government is now backing three large-scale hydro-storage projects as part of its broader energy security push.3
On the demand side, the government's clean energy strategy has entered what officials describe as a "second phase", focused on rapidly increasing electricity demand and electrification across transport, heating and industry. Montel reported the head of the country's green transition stating the aim as reversing "decades of declining power consumption."2 More demand absorbs more renewable output and softens the curtailment problem. It also raises exposure when generation falls short.
UK Carbon Allowances closed at £61.83/tCO2 as of 2026-09-13's session, with the ICE Endex TTF front-month at €79.51/MWh at Friday's close (2026-09-12). At those TTF levels, gas-fired generation remains the European marginal fuel, and the UK carbon price reflects that underlying dynamic. Any sustained drop in renewable output — whether through curtailment or low-wind periods — pushes dispatch back toward gas, supporting both TTF demand and the UKA price floor.1
The pumped-storage pipeline is the clearest forward signal to track. Eleven projects under development represent a meaningful shift in how the GB grid manages intermittency, but development timelines for large hydro infrastructure stretch across multiple planning cycles. Until storage comes online at scale, curtailment remains the grid's primary balancing tool — and traders will keep pricing weather risk into the GB power curve accordingly.3