Repair work is due to begin this week on a wind farm off the coast of Kent which has seen a third of its turbines grind to a halt since early December.
The wind turbines turned for the first time in 2005
Of the 36 turbines erected off Herne Bay - on the Kentish Flats - 12 have experienced gearbox problems.
Four have been repaired but the others have been running at reduced efficiency pending a break in the weather.
The Danish firm Vestas, which owns and maintains them, said the high failure rate was unusual.
"Unfortunately, the weather situation has not allowed us to access the turbines to restart them, and repair the remaining gearboxes," said Anders Soe-Jensen, head of offshore operations for Vestas.
The turbines have been operating on the site since August 2005, providing power to houses in Whitstable, Herne Bay, and Canterbury.
Mr Soe-Jensen said it was the first time the wind farm had experienced gearbox problems, and the cause was under investigation.
He added that, weather permitting, all 36 turbines should be working normally by the end of February.