Over at Salon, Joseph Romm argues that affordable plug-in hybrid cars are only a few years away—even if we don't see a breakthrough in battery technology. That's a bold prediction, but it'd be a huge deal if it panned out. Right now, in terms of weaning the United States off oil—two-thirds of which goes toward transportation—plug-in hybrids are far more promising than liquefied coal (suicidal), corn ethanol (still too destructive), cellulosic ethanol (too far off), or hydrogen fuel-cell cars (way too far off). 

The tantalizing bit here is that, according to one recent Energy Department analysis, we could, in theory, replace 84 percent of existing cars and light trucks—180 million vehicles—with plug-in hybrids without building a single new power plant. (That assumes the plug-ins would charge during off-peak hours and feed back into the grid during the day.) Even if that didn't happen, greenhouse emissions would still drop considerably in a plug-in world, even if the cars were being powered by dirty coal plants, although obviously the green ideal is to have the cars powered by carbon-free sources—nuclear or renewables. As a bonus, by providing distributed energy storage, plug-ins would actually make some intermittent energy sources like wind (which mostly blows at night) more viable.

Anyway, it's one of those grandiose visions that seems to be getting less far-fetched by the day. The city of Austin is already taking a hard look at the idea, as is Israel. The catch, of course, is that plug-ins would require a higher price on carbon and a fair bit of government support to become viable, though probably less support than biofuels need, and presumably less effort than it takes to police the oil supply in the Middle East.

--Bradford Plumer