Negative day-ahead prices hit 16.9% of midday half-hours in April 2026, a sharp rise that shows Britain’s power market is spending more time below zero at the very hours when wind and solar are doing the heavy lifting. For many projects backed by Contracts for Differences, those negative periods mean zero payouts.
That is why traders, generators and policy watchers are focused on April 2026 now. The share of negative-priced midday half-hours was already 11.3% in summer 2025 and 7.7% in summer 2024, but the latest reading pushes the pattern further into view as the system leans harder on renewable output.
The scale of that shift is visible in the generation figures. Gas output in January to April 2026 fell to 26.2 TWh, down 20% year on year, while wind generation rose 34% to 36 TWh. Wind reached a record 23.88 GW on 25 March 2026, and solar peaked at 16.3 GW on 23 April 2026, both signs of a grid moving toward stronger daytime renewable supply.
That growth is not occurring in a vacuum. Since 2019, the intraday structure of the GB power market has changed materially, with midday gas generation falling sharply and three north-west European interconnectors now importing into Britain during solar hours before reversing direction overnight. Evening power prices still track thermal generation costs, and the spread remains about £22/MWh above midday levels, underscoring how far pricing has drifted from the old gas-led pattern.
The friction is that more clean power is not automatically translating into more clean-power revenue. As negative-priced periods increase, they can wipe out payouts for supported wind and solar projects at the precise hours when output is strongest. That leaves the market with more renewable generation on the system, but less certainty about what that power earns when it lands.
The longer arc is just as stark. Between 2019 and 2025, UK gas generation fell 33% to 77 TWh from 115 TWh, coal went from 5.9 TWh to zero after the last coal station closed in September 2024, nuclear output dropped 35% to 34 TWh, wind rose 47% to 86 TWh and solar climbed 62% to 18.7 TWh. Net imports across the eight measurable interconnectors more than doubled to 22 TWh, while total generation edged down from 292 TWh to 289 TWh.
The gas fleet has been pushed to the margins. At 50% LHV CCGT efficiency, the 37 TWh reduction in gas-fired generation amounts to about 7.1 bcm of natural gas displaced from the power sector, capacity factors across the UK’s 30 GW CCGT fleet have fallen from 44% to 29%, and the first sub-1 GW gas half-hours appeared in 2024. Half-hours with less than 3 GW of gas generation jumped from 46 in 2019 to 2,349 in 2025, a sign that the old balancing role for gas is fading fast.
What happens next is less about a single price print than about whether Britain’s market can adjust fast enough to a system where midday supply is increasingly renewable and evening demand is still priced against thermal backup. The unanswered question is how much revenue wind and solar projects are losing as negative-priced periods become more common.
