General Motors recently announced that it is tweaking its OnStar system to try to help owners find cleaner energy to power their Chevrolet Volt gas-electric hybrid vehicles.

At the DistribuTECH Conference and Exhibition in San Antonio this week, GM showed off a prototype OnStar system which uses data gathered by PJM Interconnection, an energy grid manager for 13 states and the District of Columbia.

The data, which includes information about when electricity on a regional grid is generated from renewable sources such as windmills, is uploaded to OnStar's servers. Volt owners can then use a special smart phone app to program when to charge their Volt's battery with green energy—between 10 p.m. and 6 a.m. when most of a regional grid's power comes from hydroelectric dams, for example.

GM is currently developing and testing the advanced OnStar system with Google and its "Gfleet" of 17 Chevy Volts at Google's Mountain View, Calif., headquarters.

While GM didn't speculate when such a system might be ready for the average Volt owner, it's not the only car maker to push green energy systems for its clean cars. Ford Motors partnered with SunPower Corp. last August to offer subsidized home solar energy systems to future customers of its all-electric Ford Focus and other green vehicles.

For more information on clean-car technology, see Consumer Reports' Guide to alternative fuels.

Volt Owners May Soon Get Charged with Renewable Energy [GM press release]