Four fire engines and around 25 firefighters tackled a fire at a bungalow on Burnway in Hornchurch.
The whole of the loft space of a semi-detached bungalow was damaged by fire. There were no reports of any injuries.
The fire was in the roof space of the building and crews deployed PVStop on to solar panels.
A London Fire Brigade spokesperson said: “Incidents involving solar panels are especially dangerous as it’s difficult to isolate the electrical current they generate if they are damaged or involved in a fire.
"When tackling fire involving solar panels, crews run the risk of receiving electric shocks as the current can travel down water jets and hoses. PVStop works by blocking the sunlight that powers solar panels, so the process of converting light into electricity is stopped.
“The panels are then de-energised and the risk of electrocution is greatly reduced so crews can get closer and prevent fire spreading from a roof to the rest of the building."
The Brigade's Control Officers took the first of four calls at 1108 and mobilised crews from Hornchurch, Romford, Dagenham and Barking fire stations to the scene. The fire was under control by 1250.
The cause of the fire is believed to have been electrical.