General Motors, hoping to expand the appeal of its Chevrolet Volt, enlists its OnStar telematics subsidiary to help owners understand more clearly how much it costs to recharge the extended-range electric vehicle.

The new application software, called EcoHub, pulls overall home energy-usage data provided by an energy-data source, such as a utility or smart-meter company, and gathers specific Volt-charging information from owners with an OnStar subscription who volunteer to use EcoHub.

The app then aggregates usage data to show owners of the high-tech sedan exactly how much energy they consume daily, monthly and yearly. It also details what percentage of a home’s energy draw went toward charging the Volt.

The app uses electricity rates to calculate total energy costs and what was spent to top off the Volt’s battery pack.

“For the first time we’re able to put one of our smart-grid solutions into the hands of actual consumers,” says Paul Pebbles, global manager-electric vehicle and smart grid services at OnStar.

GM began selling the $40,000 Volt almost two years ago. The car has yet to live up to sales expectations, due to a combination of its high sticker price and skeptical buying public.

The Volt travels an average 38 miles (61 km) under battery power before a small internal-combustion engine kicks on to serve as a generator and provide electricity. It will travel a total of about 320 miles (515 km) before it must be refueled or plugged in for recharging.

The app also features a “Ticker” screen that tracks national values for total miles driven, total EV miles driven and gallons of fuel saved.

GM and OnStar initially will test the app as part of its partnership with Pecan Street, an Austin, TX-based research and development group focused on testing energy, wireless and consumer electronics technology. The auto maker hopes to make it available to all Volt owners soon.