On Monday, Volkswagen subsidiary Electrify America announced a partnership with Tesla to deploy Powerpack batteries (the utility-grade version of the stationary storage, Tesla Powerwall) at 100 charging stations throughout the US.

The plan is to use the 210 kilowatt (kW), 350 kilowatt-hour (kWh) batteries as local reserves during periods of high demand, when utilities might charge a company like Electrify America higher rates to provide electricity. On particularly hot days as utilities struggle to meet the needs of air conditioning, for example, higher electricity rates can kick in. That’s where reserves of power can help a company like Electrify America shave down the amount of power it’s demanding.

The Powerpacks are modular, and a press release from Electrify America says that the company may add more Powerpacks to certain locations over time. Giovanni Palazzo, CEO of Electrify America, said in the same press release: “With our chargers offering high power levels, it makes sense for us to use batteries at our most high demand stations for peak shaving to operate more efficiently. Tesla’s Powerpack system is a natural fit given their global expertise in both battery storage development and EV charging.”