Five fire engines and around 30 firefighters were called to a fire on Drury Way in Wembley.
Approximately 100 solar panels situated on the roof of a large commercial store were alight. A small part of the roof has also sustained some damage.
Around 250 people were safely evacuated from the store. There have been no reports of any injuries.
The Brigade received the first of 12 calls at 1035 and Control Officers mobilised crews from Park Royal, Wembley, Willesden and North Kensington fire stations to the scene. A 32-metre turntable also attended and has been used as a water tower to help extinguish the fire from above.
The fire was extinguished by 1244.
The fire is believed to have been caused by resistive heating.