In the industrial hub of Wuxi near Shanghai, car owners recently took part in China’s largest experiment to rewire the grid and take advantage of its world-leading fleet of electric vehicles.

Instead of charging up after plugging in, 50 EVs did it the other way around. For 30 minutes, the cars combined to feed around 2 megawatts of electricity into the grid, enough to fully power 133 houses for a day, according to a report from state-owned CCTV.