Toyota Motor Corp. plans to sponsor more than 15,000 customers who live in California and own certain Prius Prime or RAV4 Prime plug-in hybrids to join a program that tracks any carbon generated from charging those vehicles and offsets it with renewable energy.

The automaker calls the program Clean Assist, and it is providing it at no cost to customers through the Toyota app.

Once customers are enrolled, the smartphone app tracks the amount of electricity the vehicle used during charging. Toyota then buys an equivalent amount of California-sourced renewable energy certificates — used to underwrite the expansion of renewable energy generation and transportation.

Evidence of the purchased renewable energy certificates is sent to the California Air Resources Board, generating low-carbon fuel standard credits for the automaker. (Each low-carbon fuel standard credit is equivalent to 1 metric ton of CO2 that is saved.)

To be eligible to participate, owners must have a Prius Prime or RAV4 Prime with telematics equipment, a Toyota spokesman explained. Inputting the vehicle’s information into the app will let consumers know if the vehicle is eligible.

The app will track vehicle charging for participants regardless of where they plug in, and 100 percent of that electricity will be converted to renewable power. Participants will also be able to see how many metric tons of CO2 they’ve avoided generating through the program.