Faster car chargers that provide 11kw charging can be installed in 100-amp homes, but there is a risk of putting too much demand on the system if other electrical appliances are used at the same time, leading to blown fuses and blackouts, experts said. Extra chargers add to this risk.  

Electric car drivers have also been quoted hundreds of pounds to upgrade their power systems from 60 or 80 amps to 100.

Ben Nelmes, the head of policy at NewAutomotive, a transport research organisation, said: “Some of them will charge an absolute fortune – or worse they’ll refuse to do it.

“People will sign a lease on an electric car, they’ll call up their electricity supplier and say: ‘I want to have an electric car, I want home charging, I need to upgrade my fuse box.’

“The electricity supplier will then ring up the distribution network operator, and the distribution network operators sometimes say no. And that causes chaos for people, which is really bad – they’re trying to do the right thing and switch to an electric car.”

National upgrade to improve substations and cables

A spokesman for SP Power Networks said it was planning to invest in mass upgrades and did not charge for upgrades to a 100 amp supply.

“A typical electric vehicle can double household consumption, and heat pumps can have a similar or even greater impact,” he said.

“In the majority of cases, these low carbon technologies can be safely accommodated by the cables and assets we use to provide the customer with their electricity supply.

“Connection requests involving both upgrading a domestic supply from a single supply to three-phase and requiring expensive network reinforcement are rare.

“The current cost of this upgrade can vary significantly, depending on the work required, and is in line with the charging methodology used by all GB distribution network operators.”

A national upgrade programme, slated to begin in 2023, is expected to improve substations and cables to allow them to cope with the demands of thousands of domestic heat pumps and car chargers, which the existing grid was not designed to handle.

A spokesman for the Department for Business, Energy and Industrial Strategy said: “The vast majority of domestic consumers will not need to pay for an upgraded connection to accommodate a heat pump and electric vehicle charger.

“Where costs are chargeable, these are regulated by Ofgem to ensure they are calculated appropriately.”

The department added that an Ofgem review into the cost of new connections, which could see charges drop, is ongoing.