Audi is investigating the potential for vehicle-to-grid charging systems for its future electric cars.

Working with energy infrastructure company Hager Group, Audi has developed an E-Tron Sportback prototype capable of vehicle-to-grid charging. The prototype is being used to test how energy stored in an EV's battery could be sold back to the grid or used to power a home.

Where would such a system make sense? Imagine you had solar panels collecting energy during the day. Any excess energy you don't use in your home can be stored in your car. Then, during the busy hours at night when electricity rates are high, your car can sell the stored excess energy back to the grid. The car then charges itself up from the grid overnight when electricity rates are lower. In this way, you don't even have to have solar panels to benefit.

There's another benefit, too. During a blackout, your car could be used to power your home. Audi says the typical EV battery could power a home for a week.

Charging software manages the optimum use of the battery, helping to maximize the cost-effectiveness of the system. This software would also ensure there's a minimum state of charge so that the owner won't be stuck if he or she needs to suddenly use the car. The owner doesn't have to do anything apart from plugging in their car. For its prototype, Audi is using a DC wall box that enables charging at up to 12 kilowatts.

“Maintaining mobility is at the center of our attention,” Martin Dehm, technical project manager for vehicle-to-grid charging at Audi, said in a statement. “Customers therefore don’t need to restrict themselves in order to make (vehicle-to-grid) charging suitable for everyday use.”