UK electricity supply margin set to hit summer low in June

The UK’s power generation surplus is forecast to drop below 10GW for the first and only time this summer during week 24, according to the latest data from system operator National Grid.

The supply margin, which takes into account the level of generation that will be surplus to demand requirements during the forecast daily half hour of peak demand, is expected to measure just under 9GW in the second week of June.

The supply margin is not forecast to drop as low again until the second week of November.

Maintenance plans

Combined cycle gas turbine (CCGT) generation is responsible for the majority of the capacity withdrawal from the market, with the start of summer maintenance at RWE’s Pembroke power station set to make the biggest dent in the surplus.

At 60% thermal efficiency, it is one of the most efficient plants in the UK’s CCGT fleet and frequently one of the first to be called on to ramp up generation in response to demand needs.

Despite wind generation out-turning close to 6GW during much of Tuesday, four of the plant’s five 415MW units were producing at full capacity for most of the day, according to data from the UK’s balancing service operator Elexon.

The entire plant is not expected to return until the start of Week 30, the penultimate week of July.

EDF’s 435MW West Burton B unit 3 CCGT will also go offline at the start of Week 24, although this will be more than offset by an increase of 700MW from the Immingham plant.

Major coal-fired plants that are scheduled to go offline during Week 24 include Eggborough’s 500MW unit 3 and EDF’s 500MW West Burton unit 2.

One of the 500MW units at SSE’s Fiddlers Ferry coal-fired plant is also scheduled to stop running, although this will be offset by the return of another unit at the power station.

Nuclear availability is not expected to drop too significantly from Week 23, with the only major change in output occurring at Hunterston B, which will reduce availability by 400MW.

Returning plant will help propel the surplus back above 11.5GW at the start of Week 25, according to National grid data.

Price effect

Although the summer period holds less threat of surprise spikes in demand that could pressure supply margins, the loss of one of the UK’s most efficient flexible plants could force older and more expensive power units to switch on when peak periods coincide with low solar and wind generation.

This would add a premium to the Day-ahead contracts at times of low renewable forecasts.

However, trading on the front-month contract in recent sessions has pursued a bearish trajectory and even resisted the strength of its equivalent NBP natural gas contract on Tuesday despite the traditionally ingrained link between UK power and gas markets.

Source: ICIS Energy