The National Grid said its site at Sellindge in Kent was evacuated on Wednesday morning following the fire.
The blaze and planned maintenance means the Interconnexion France-Angleterre (IFA) interconnector will be offline until Sept. 25, and only half of its two gigawatt capacity available until March 2022.
Prices of electricity on the day-ahead market peaked at £2,500.01 ($3,476) per MWh for delivery between 7 p.m. and 8 p.m. on the N2EX exchange, with an average daily price of £424.61 ($587.67).
This compares with an average in August of £106.83 ($148.54), and an average across 2020 of £35.26 ($48.8).
The fire at the IFA site broke out in the early hours of Wednesday.
A National Grid spokesman said it expects to “continue supplying electricity safely and securely” despite the incident.
It added, “Our investigation is ongoing and we will update the market with any changes as necessary.”
The link can carry up to 2GW of power, and had been importing electricity from France in recent days, after UK prices hit a record high of £540 ($747.37) per MWh on the wholesale energy market.
Rising energy prices has been a key concern for economists in contributing to inflation hitting a nine-year high in August.
By Alexander Britton