An Audi AG plant that converts surplus wind power into natural gas can help stabilize the German electricity grid, according to TenneT TSO GmbH.

The 6-megawatt unit in Werlte, northwestern Germany, passed a test by TenneT and has been deemed “fit” to sell excess capacity to grid companies trying to balance supply and demand, TenneT said in a statement Wednesday, quoted by Bloomberg.

“This is a further step on the path to better integration of renewable energies”, TenneT said in the statement. “Services that stabilize electricity supply have so far been mainly provided by conventional power plants.”

Germany’s grid operators procure about 4 gigawatts of positive and negative balancing energy from hydropower, gas and biogas plants to be able to take out or add capacity to the grid when production fluctuates. Plants require a license for that.

Audi’s power-to-gas plant, which started operating in 2013, uses electricity from wind turbines to turn water and carbon dioxide into synthetic methane, which is fed into Germany’s natural gas grid for storage.