Northern Ireland consumers could face a bill totalling tens of millions of pounds because of a breakdown in electricity links to Scotland.
The warning comes after it emerged that the Moyle interconnector, which transfers power across the Irish Sea, has suffered a fault — for the fourth time in 22 months.
As a result of the defect located offshore, half of its 500 megawatt capacity has been lost since June 23.
Mutual Energy, which owns the interconnector, said a “locate and repair programme” would take six months to complete.
That means that parts of Northern Ireland could face rotating electricity blackouts this Christmas because of the persistent problems.
In a statement, Mutual Energy admitted that the problems were serious, adding that it had not been decided whether the defect is to be repaired.
“The number and nature of the faults is abnormal for underground cables and raises questions in relation to the future reliability of part of the cables,” it read. “A more cost-effective approach could involve replacing entirely the unreliable part of the cables by laying a standard back-up support cable, work which would take a number of years.
“In the meantime, we could reconfigure the cables to allow Moyle to operate reliably at half its full capacity.”
A final decision on whether or not to repair the fault will only be made when Mutual Energy has concluded all the fault location work. The fault is located offshore, approximately 7km from the Scotland converter station.
Economist John Simpson said:“Consumers face a bill for many millions because the financing of the interconnector is guaranteed through the regulatory system.”
And he added: “In the worst case scenario, Northern Ireland might not have enough electricity for peak demand in a very cold winter.”
The Moyle interconnector is a link between Auchencrosh, South Ayrshire, Scotland, and Ballycronan More, Co Antrim, that transfers electricity across the Irish Sea. It went into service in 2001 and is owned and operated by Mutual Energy, a not-for-profit company which manages energy assets for Northern Ireland's energy consumers.