As blackouts become more common during California’s fire season, utility PG&E is looking to electric vehicles as one potential backup plan for the state’s stressed-out grid. It’s been working with carmaker BMW to test whether electric vehicles could provide power when there is an outage or not enough energy to meet demand.

Theoretically, a network of EV batteries could one day provide a backup source of energy for communities called a “virtual power plant.” But first, automakers and utilities will need to see if it’s worth it to work with each other. Then, they’ll need to get their customers on board, too. BMW and PG&E’s partnership is a sort of test run for that.

The two companies started working together in 2015. Until now, the pair has mostly focused on increasing the amount of renewable energy used to charge EV batteries. It’s a strategy called “smart-charging” that encourages EV owners to charge their cars during times of the day when there is less electricity demand and more available renewable energy, like solar power. Starting this week, they’re expanding the program, and PG&E customers who drive electric or hybrid BMWs can apply for a 24-month “smart-charging” pilot program and earn cash incentives when they charge their cars during recommended hours.

The cars won’t be selling energy back to the grid, but the program could give PG&E some early insight into when and where drivers charge their cars, according to Adam Langton, an energy services manager at BMW of North America. That’ll be key for getting drivers on board for vehicle-to-grid charging.

The two companies also said they would begin testing hardware in a lab this year. BMW needs to know how often PG&E might ask drivers to connect to the grid and what toll that might take on the car. PG&E needs to know how much energy a car battery can provide and for how long. They’re also figuring out what additional infrastructure might be needed at someone’s home and across the grid to make all of this happen.