Steve Shadley/KJZZ

The Phoenix Zoo.

One of the big challenges to a carbon-free grid will be to replace gas vehicles with electric. The Phoenix Zoo has built some necessary infrastructure to help with that transition.

A recent study at Arizona State University found that building a clean energy grid will require a lot of charging stations.

The zoo recently unveiled 20 solar-powered stations near its entrance, which will be free initially.

Users will eventually pay an hourly fee for the service, though it is not clear how much.

Salt River Project will feed leftover energy from the panels into the power grid.