Octopus Energy has urged its customers to avoid using electricity during the deepest solar eclipse in almost 30 years.

Britain’s biggest household energy supplier has warned people not to use washing machines, dishwashers, and other plug-in devices between 6pm and 8pm on Wednesday.

The eclipse is expected to block up to 95% of sunlight as the moon moves the sun, plunging solar generation across the UK.

It comes as countless Britons will be looking to run air conditioning units, fans, and refrigerators amid the latest forecast heatwave.

The slump in solar power could knock out as much as 1.3GW of supply, according to the National Energy System Operator (NESO).

This means gas-fired power plants will have to be switched on to make up for the shortfall and to steady the grid.

There has been no suggestion that the eclipse could trigger outages, but the energy supplier has encouraged people to use less energy to avoid excess carbon emissions.

Octopus Energy is offering rewards to customers who cut their usage during the eclipse. Those who signed up to take part in the supplier’s “saving sessions” will be given a free hour of electricity to use the next weekend.

The “saving sessions” scheme means households can earn rewards for using less electricity when wind or solar power is scarce.

If enough households avoid using electricity during the eclipse, Octopus Energy believes the UK can avoid having to turn on gas-fired stations.

“Household flexibility is one of Britain’s biggest untapped energy resources,” the supplier said. “Octopus estimates homes could provide a whopping 13 gigawatts of flexible capacity to support the electricity system – particularly through smart appliances, EVs and home batteries – yet only a fraction of this potential is currently being used.”

Neso has said the eclipse’s impact on the grid will be manageable and that it had implemented planning for “over a year”.