About 2,200 homes in west London were affected by a power cut.
Southern Electric reconnected about 1,400 homes in Chiswick and Acton at about 1400 BST and power to all has now returned.
The firm said the outage was caused by a faulty underground cable which engineers replaced with a new section of cable.
Up to 500 homes and businesses in Westminster were also affected by a power cut. All power has been returned.
Millbank studios, where the BBC broadcasts some of its political coverage, lost power for about five minutes.
The energy supplier said Bridge Street and King Charles Street, in Westminster, had also been affected by the problem.
UK Power Networks, who are responsible for electricity in the area, said the power outage was caused by an underground fault at about 0900 BST.
A Southern Electric spokesperson said the company apologised to those people affected by the power cut in west London.