A report by the Green Alliance (www.green-alliance.org.uk) ‘think tank’ claims that the UK’s energy networks are not ready for an increase in the number of electric cars and solar panels — expected by 2020.

It says that “a cluster of battery-powered cars” could result in 1% of the UK experiencing unplanned drops in voltage — potentially damaging electronic equipment — and it warns that as few as six electric vehicles located near each other could lead to such “brown-outs”.

It said that charging one car requires as much electricity as a typical home uses in three days, so simultaneous demand at a local level could damage networks without costly reinforcements.

Dustin Benton, the author of the report, said that electric-car sales were up 56% last year (on 2015 figures), and he believes falling costs will lead to a rapid uptake.

“We predict a similar growth in the next few years in the installation of solar panels, which are already disrupting the energy system.

“Electric cars and solar panels will soon be viable without subsidy, and the Government will no longer be able to constrain them, so action must be taken now to manage their impact.

“Otherwise, there could be damage to power networks from electric-car charging or solar panels unable to connect to the grid because of bottlenecks. That in turn could trigger emergency policy making, which would be bad for investment.”

A National Grid spokesman said: “Growing use of solar power and electric cars will change the way the energy system is managed, but we have been dealing with evolution in the energy sector for decades, and these latest changes also present great opportunities.

“For example, electric vehicles can be used to help feed energy back into the system at key times, while solar power will play a crucial role in providing ‘clean’ energy, as coal-generated power stops being used.”