Four fire engines and around 25 firefighters were called to a fire at an electrical substation next to a hotel on Collingham Road in Kensington.
The substation was destroyed by the fire and a distribution board was damaged. There were no reports of any injuries.
The Brigade's 999 Control Officers have taken 10 calls to the fire.
The Brigade was called at 1047 and the fire was under control by 1317. Fire crews from Kensington, Chelsea, Paddington and Fulham fire stations were at the scene.
The Brigade's Fire Investigators believe the fire was caused by a failure of a 3 phase mains distribution board.