What’s the price of charging that Chevy Volt on your household electricity bill? And how big a share of your total power use is that plug-in sucking up, anyway?  

Volt owners in Austin, Texas’s Mueller neighborhood can now answer questions like these. General Motors announced Friday at the SXSW Eco conference that it’s rolling out its new EcoHub app as part of its participation in Austin’s Pecan Street Project smart grid project, meant to tie together plug-in vehicles, rooftopsolarpanels and energy-smart home systems.

It's the first app developed using the proprietary smart grid APIs that GM released for its OnStar car navigation system back in February, and for now, it’s only available to Pecan Street customers, who have bought 55 Volts and counting under a special rebate program meant to saturate the neighborhood with electricity-thirsty plug-in cars.

Like every other plug-in electric and hybrid car maker, GM wants to network its cars so that both customers and utilities can track and control their charging patterns. Adding hundreds of plug-ins to a neighborhood could overwhelm the grid, if they’re all plugged in at once. But managing their charging could allow plug-ins to serve grid balancing and support services that could make them assets, not liabilities, to the power system.

In the case of GM’s new app, it’s combining the on-board Volt system for tracking and managing battery charging with the smart meter data coming from utility Austin Energy, which includes pricing. That combines the three variables of time, power and price to deliver costs of charging the Volt, compared to overall household power usage, in a way that can be hard to do for plug-in owners who use household power to charge their cars at night.

To be sure, EV charging stations, whether they’re slow-chargers in the garage or fast-chargers on the highway, already come with their own technology for tracking power and pricing. That allows EV charger networking companies like ECOtality or ChargePoint (also known as Coulomb Technologies), or private charging networks like NRG Energy’s eVgo network, to set prices, track and bill their own customers on their own terms.

Likewise, plug-in cars from Nissan, Mitsubishi, BMW, Ford, etc. already have onboard battery management systems that control when and how fast they charge, and most come with telematics that allow them to communicate that data to platforms like GM’s OnStar system.

But combining power and price can be tricky, particularly for utility customers trying to choose between a growing variety of utility pricing programs for EV owners. The Union of Concerned Scientists reported last month that California plug-in owners could see differences of as much as $400 per year on their power bills for charging, depending on which rate programs they signed up for, to take one example.

Tools like EcoHub could be useful in solving this problem. This first version will only be available for testing in the Pecan Street Project, but GM hopes to offer them to the general public in the future. It can integrate on a utility-by-utility basis, though it’s hoping that common data formats like those being developed under the White House’s Green Button initiative could make getting data to customers much faster and easier, a GM spokesman said. 

Eventually, of course, utilities want to go beyond just knowing what their customers’ plug-in cars are doing, and start doing something about it. Utilities and governments around the world are building out networked charging infrastructure, first to collect data, but later to actively control plug-ins via schedules or push commands that can help avoid grid overloads and imbalances.

GM’s EcoHub app isn’t built to do that kind of stuff, but of course the Chevy Volt is one of many plug-in cars being tested for these more advanced vehicle-to-grid (V2G) applications. But first, let’s get the data in the hands of the customer.