Heatwave pushes Great Britain's grid operator to call for extra electricity from power plants

Neso seeks extra capacity

Great Britain’s National Energy System Operator asked power plant operators to provide about 1,900 MW of extra capacity on Wednesday as a heatwave and low wind tightened the grid’s evening margin.

The request came after Neso issued an electricity margin notice late on Tuesday, June 23, ahead of the Wednesday peak. The operator said the highest demand was expected between 7 pm and 10 pm on June 24.

Neso said the system was not at risk and that the notice was a routine balancing step, even though such warnings are more common in winter than summer.

Why the grid was tighter

The immediate pressure came from extremely high temperatures across Great Britain and the wider continent, along with weak wind generation. Heat can push electricity use higher, especially when people rely more on cooling.

The Guardian reported that record June temperatures of up to 39C were expected in south-east England, adding strain beyond the power system and affecting transport, schools and hospitals.

Wider European pressure

The heatwave was also lifting electricity prices across Europe and reducing output in some markets. Earlier reporting said Neso had already secured around 1.5 GW of extra electricity for the evening peak.

In France, Le Monde reported that several EDF nuclear reactors faced uncertainty because of hot river water, while grid operator RTE said the overall system remained secure.

What to watch

The next question is whether Neso extends the notice, issues another warning for later peaks, or relies on imports and generator responses to keep margins comfortable.

The episode is a reminder that summer can stress a power system even without a blackout threat, and that balancing interventions can carry costs for consumers and businesses.