The UK’s biggest energy supplier is encouraging Britons to use less electricity during the solar eclipse tomorrow, because solar power generation will plummet.

Octopus Energy urged its 8million customers not to use washing machines, ovens, dishwashers and other plug-in devices between 6pm and 8pm.

Tomorrow’s hotly anticipated eclipse will see solar generation plunge at a crucial time of day when electricity demand rises as millions of people come home from work.

Octopus has now warned customers the eclipse will ‘briefly knock out a chunk of Britain’s solar power’ and possibly require more fossil fuel power generation.

The National Energy System Operator (Neso), which runs the UK grid, said the eclipse could cut solar supply by up to 1.3 gigawatts tomorrow – enough to power at least 500,000 homes.

Extra gas power stations may therefore have to be fired up, but Octopus said this need will be reduced if enough households delay using electricity for a short time.

The firm said it would monitor those who use less electricity than usual during that two-hour window and give them one hour of free daytime electricity this Sunday at a time to be confirmed.

Read more: Britain’s biggest energy supplier tells customers to avoid using electricity during the solar eclipse because of hit on renewable generation