Great Britain faces electricity supply shortfall during solar eclipse

Event expected to hit solar power just as fifth heatwave of summer increases use of air conditioning and fans

Great Britain faces a shortfall of electricity supplies on Wednesday evening as the near total solar eclipse is expected to wipe out solar power generation.

The government’s electricity grid operator raised an official alarm that there is currently not enough power generation expected as the moon blocks up to 95% of the sun over parts of the country, the most dramatic eclipse visible in Great Britain since 1999.

The darkening of the skies is expected to wipe out between 300 megawatts and 1,100MW of solar power, just as the fifth heatwave of the summer raises demand for electricity to run air conditioning, fans and refrigeration systems.

The National Energy System Operator (Neso) had first anticipated a shortfall of more than 1,700MW, according to a warning on Tuesday night, about the equivalent capacity of a solar farm the size of 8,500 football pitches. Under a second market notice issued on Wednesday morning, it said the shortfall remained about 1,200MW.

A spokesperson described the warning notice as a “routine tool” that means it is asking the energy market to make any additional capacity generators may have available. It added that the notice was a “precautionary measure to the market” because of the solar eclipse and there was “no risk to customer electricity supplies”.

To resolve the shortfall, Neso is expected to make lucrative payments to energy generators to help fill the gap, which will be covered through consumer energy bills.

The looming eclipse has caused electricity market prices to climb to highs last seen during the heatwave in late June, according to market analysts at LCP Delta, a consultancy and data provider.

The price of electricity for Wednesday evening rose to more than £211.40 per megawatt-hour at 7pm, its highest level since 30 June. If market prices remains elevated through the day, this could lead to higher prices offered to gas power plants to fill the shortfall in electricity supplies during the eclipse.

The power supply squeeze has prompted Britain’s biggest household electricity supplier, Octopus Energy, to encourage customers to avoid running washing machines and dishwashers between 6pm and 8pm on Wednesday to help save electricity.

In return, the supplier is offering eligible customers a free hour of electricity to use on Sunday. If enough households delay using electricity for a short time during the eclipse, it could reduce the need for Great Britain’s electricity system operator to fire up extra gas-fired stations to replace the lost solar power, according to the supplier.