If electric cars are supposed to clean up the environment and reduce global warming—and they are—EV drivers would like to rely on 100 percent renewable energy to do charge. And charging networks are striving to provide it.

Many, including Tesla with its Supercharger stations, are building new charging stations with solar canopies or stations with battery storage, or both.

READ MORE: Charging network EVgo goes tagless, tests battery buffers at stations

But there's more than one way to deliver clean power. Charging network EVgo announced last week that it signed contracts with all its power providers to deliver clean energy to all its chargers. 

The company claims it will be the first charging network in the U.S. to provide 100 percent renewable electricity, and that it already receives all its electricity in California from wind and solar power. It did not specify whether all the new renewable power it will buy elsewhere will come only from wind and solar or whether it could include energy from other renewable sources such as hydro power or biomass. 

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Of course, that doesn't mean that every electron that flows into the battery came only from a windmill or solar panel. It only means that the money drivers pay to charge flows back to support such endeavors. As such systems expand, though, it pumps larger buckets of funding to building new renewable energy sources.

EVgo has also installed a variety of types of battery backups at several of its California stations to test what types of systems remain the most cost effective over the long run. It installed its first fast-charging solar-array canopy at a fast-charge station in Baker, California, in the desert between Los Angeles and Las Vegas last year.