For the first time in 12 years, the UK exported more electricity than it imported in the second quarter of the year.
The surplus was used to help France make up a shortfall in electricity as it has been experiencing extended nuclear outages that have hiked prices higher.
Electricity and gas leaving the UK both surged around 600% in the three months to June compared with the prior year, government data showed.
Britain’s power generation jumped by 8.2% as domestic demand eased 5.5% lower, with the last time the tables turned being in 2010.
It is unknown whether such high volumes of exports could be sustained, with demand expected to soar in the winter months.
There are likely to be times when power supplies are not enough to meet demand this winter, with the grid operator potentially being forced to shut off some homes, a Lane Clark & Peacock study showed.
Phil Hewitt, director at energy consultancy EnAppSys, commented: “Unfortunately, we can’t both take power from each other in the winter.
“There is a contradiction, so there will be closed interconnectors.”
The UK has been providing power to countries, especially France, which has 56 nuclear reactors operating at less than half capacity due to ongoing outages.
With domestic demand in the UK almost certainly set to rise this winter, neighbouring countries may need to look elsewhere for electricity.
The French government anticipates asking homes and businesses to slash consumption this winter to prevent power cuts.