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Chart of the Week


We’ve got the power: T-4 Capacity Market results

Lee Drummee
Lee Drummee

On 6 March, the EMR Delivery Body (National Grid ESO) published the provisional results of the T-4 Capacity Market (CM) auction for Delivery Year 2023-24. The clearing price of the auction was £15.97/kW/year, the highest value since the 2016 auction, procuring 43,749MW of de-rated capacity. The clearing price was significantly higher than the £6.44/kW/ year in the recent T-3 auction. In this Chart of the week, we explore some of the reasons for this.

Existing generation accounted for 33,983MW, equivalent to 77.7% of overall capacity compared to 81.9% in the T-3. Only 4.0GW of nuclear was awarded agreements, down from 5.9GW in the T-3 auction. Hunterston and Hinkley B had already opted out of the auction, while Heysham 1 and Hartlepool were unsuccessful in winning agreements.

This allowed more “space” in the auction for new build sites, with 1,798MW of de-rated new build capacity awarded agreements across 95 individual CMUs. The Keadby 2 CCGT was the largest of these, with a de-rated capacity of 803.7MW and representing the first new build CCGT to win an agreement since the first T-4 auction in 2015.

The next biggest new build plant was Ferrybridge Multifuel 2 at 66.1MW. However, the success of both these new build projects was somewhat expected, with SSE already committed to building Keadby 2, while the Ferrybridge site entered commercial operation in December 2019.

Battery storage accounted for 114.5MW of de-rated capacity, split between 1-hour duration (94MW) and 2-hour duration (20.5MW). This included the 50MW battery at the Whitelee windfarm.

New build onshore wind was again successful, with three more projects awarded agreements. The successful plants; Whitelaw Brae (57MW nameplate, 4.2MW de-rated), Aberarder (50MW, 3.7MW) and Blary Hill (35MW, 2.6MW) will also benefit from a clearing price ~2.4 times higher than the T-3 auction.

The only windfarm not to win an agreement was Vattenfall’s South Kyle with a nameplate capacity of 234.8MW. However, with the potential re-integration of “Pot 1” technologies in the next Contracts for Difference allocation round, missing out on a CM agreement allows the project to participate in the next CfD round if they desire. The next opportunity for new build plant will be the prequalification for the 2024-25 T-4 auction, which will commence in July 2020.


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