The 2029/30 T-4 GB Capacity Market auction cleared at £27.10/kW/yr. This reduces the cost of new agreements to consumers by more than half relative to the £60+/kW/yr seen in the previous three T-4 auctions.

40.1 GW of de-rated capacity was procured against a target of 39.4 GW. Gas dominated awarded capacity, with refurbishing units accounting for 31% of the total following the lowering of capex thresholds this year.

Batteries secured 1.2 GW de-rated across 4.1 GW of connection capacity. Two-hour systems led on connection capacity, but four and five-hour systems combined won more de-rated capacity.

Interested in the T-1? Read our analysis of the 2026/27 T-1 auction results.

Refurbishing gas drove the T-4 Capacity Market surplus

Of the 50.4 GW of de-rated capacity that qualified, 44.1 GW entered the auction. It cleared in round 10 at £27.10/kW/yr, with 91% of entering capacity awarded an agreement.