Great Britain’s grid operator has warned of an anticipated electricity supply shortfall on Wednesday evening as a near-total solar eclipse sharply reduces solar generation while hot weather raises demand for cooling. The National Energy System Operator said the notice was precautionary and that customers’ electricity supplies were not at risk, but it may need to pay generators to provide additional capacity, with costs ultimately borne through bills.

The eclipse could remove between 300MW and 1,100MW of solar output, while the expected shortfall was revised from more than 1,700MW to about 1,200MW. Evening wholesale power prices rose above £211.40 per megawatt-hour at 7pm, their highest since 30 June, and Octopus Energy asked customers to avoid using washing machines and dishwashers between 6pm and 8pm to reduce the need for extra gas-fired generation.