With everyone

» READ MORE: debating the "big three" auto-industry bailout,

it's a good time to recall one of Obama's promises for "change": Namely, switching the entire White House fleet to electric cars -- or nearly electric, in the form of plug-in hybrids.

With plug-in hybrids you can save money by deriving the energy to charge your battery from a cheaper home-electric-grid source, or you can choose to make the car greener by sourcing that electricity via solar or wind power. Whether you can do both at the same time is still up for grabs.

At the Green Festival last month I talked with Charlie Darlow about the technology and the lifestyle of plug-in hybrids, and came away with the impression that it's still quite an expensive option requiring significant capital outlay for the average consumer. Still, Obama's not the average consumer, and I wanted Charlie's opinion -- as an expert on the feasibility of plug-in hybrids -- on whether the president-elect will keep his promise. Here's a

» READ MORE: four-minute audio clip of that exchange