A Major Solar Milestone: The Grid Ran on Over 50% Renewables for a Record Stretch

The energy transition is full of moments that sound impressive in a press release but dissolve on closer inspection. Record renewable percentages achieved on a mild spring Sunday at 3am, when demand is low and wind is high, say less about a grid's decarbonisation than they first appear. The more meaningful milestones are the ones that happen under real demand conditions, over sustained periods. Britain's National Grid has been logging more of those lately, and the trajectory is worth examining properly.

In the first half of 2026, the GB electricity grid ran with renewables supplying more than 50% of total generation for sustained multi-day periods on multiple occasions, a threshold that would have been considered practically unreachable a decade ago. Wind, both onshore and offshore, has been the dominant driver. The UK now has over 30 gigawatts of installed offshore wind capacity, making it the largest offshore wind market in Europe and second globally only to China.

The Storage Gap Is Closing

The challenge with high renewable penetration has always been intermittency. Wind does not blow at convenient times, and solar generation peaks at midday regardless of when demand peaks. The traditional answer was to keep gas peaker plants in reserve, running them up whenever renewable output dropped. That model still exists, but it is being supplemented, and in some windows replaced, by grid-scale battery storage at a pace that accelerated sharply in 2025 and 2026.

Grid-scale lithium iron phosphate (LFP) battery systems, which favour cycle life and safety over energy density, have seen substantial capacity additions in the UK. National Grid ESO has been contracting for balancing services increasingly from battery storage rather than exclusively from gas. The cost per megawatt-hour of installed battery storage fell by roughly 40% between 2022 and 2025, according to BloombergNEF data, and project pipelines in planning suggest that trend is continuing.

The combination of increased renewable generation capacity and growing storage capacity is what enables sustained high-renewable periods rather than one-off peaks. When you can store excess midday solar or overnight wind and dispatch it during the evening demand peak, the arithmetic of running a high-renewable grid becomes significantly more tractable.

What Still Has to Change

Honesty requires acknowledging what the 50% milestone does not mean. The UK grid still uses natural gas for a substantial portion of generation, particularly in winter when heating demand is high and solar output is minimal. Industrial heat, shipping, and aviation are largely untouched by the electricity grid's decarbonisation. And the transmission infrastructure needed to carry power from where renewables are generated, primarily the north of England and Scotland, to where demand is concentrated, primarily the south of England, remains a bottleneck that is years from resolution.

National Grid's transmission investment programme, under the Holistic Network Design framework, plans to build new high-voltage direct current interconnectors and upgrade existing AC links. The timelines run into the early 2030s for the most significant additions. Until that infrastructure is in place, there will be periods where renewable generation in Scotland is curtailed simply because there is no capacity to move the power south, which is an expensive and carbon-costly outcome.

The Bigger Picture

Britain's renewable progress is real and should be acknowledged as such. Offshore wind costs have fallen dramatically, the planning and consenting system, though still frustrating, has approved enough capacity to underpin the current trajectory, and the financial models for new projects are now more stable than they were during the interest rate turbulence of 2022 and 2023.

The honest question is whether the pace is fast enough. The Climate Change Committee has set clear milestones for grid decarbonisation, and the current trajectory needs to accelerate further to stay on track. The milestones being celebrated in 2026 are genuinely impressive. They are also the minimum required, not the destination.