UK generates record 9.9TWh solar in H1 2025, boosting storage

The UK has logged its strongest six months of solar generation on record, and the grid implications are coming into sharp focus. A new analysis from clean-energy think tank Ember shows solar output in the first half of 2025 climbed 32% year on year to a record 9.91 TWh. Solar has smashed monthly highs five consecutive months beginning in March 2025, while 8 July set a new instantaneous record with 14 GW on the system—a 44% increase in the UK’s yearly solar peak compared with five years ago.

Two forces drove the surge: record sunshine and a rapid build-out of PV. According to Solar Media Market Research, the UK added more than 2 GW of solar PV in H1 2025—close to the capacity added in all of 2024 and the strongest start to a year in a decade—lifting operational capacity to over 22 GWp.

From generation records to system needs

To understand why storage is moving center stage, zoom out to total generation. The UK produced ~300 TWh in 2024, with renewables supplying 50.4% (up from 46.4% in 2023). On a seasonal basis, H1 2025 is estimated at ~150 TWh, putting solar’s share at roughly 6.6% across the half-year—even as renewables (especially wind) dominated in some months (e.g., June wind ~31% vs gas ~21%).

That progression marks solar’s shift from marginal to material. But it also exposes the classic intermittency challenge: big midday surpluses and low-light deficits. As record solar increasingly pushes daytime supply toward—or at times near—system peaks, the grid must absorb excess, avoid curtailment, and shift energy into the evening peak.

Storage steps up

Market indicators suggest storage is already responding. In H1 2025, UK battery energy storage project completions jumped 78%, while planning applications rose 25%. Strategically, storage is the bridge between record PV and reliable supply: it captures surplus, reduces curtailment, flattens ramps, and displaces gas during peak demand. Policy direction aligns with this, with government plans targeting 23–27 GW of batteries by 2030 to provide flexibility and resilience.

Why it matters

• For the grid: Batteries convert variable solar into dispatchable capacity, easing congestion and enhancing frequency response and reserve.

• For economics: Storage raises the value of each incremental PV megawatt by shifting energy to higher-priced hours and cutting balancing costs.

• For net zero: Pairing large-scale solar with storage accelerates coal and gas substitution without sacrificing reliability.

The UK’s 9.91 TWh solar record in H1 2025 is a milestone—and a mandate. To turn intermittent highs into everyday reliability, energy storage must scale as quickly as PV.