Photos: Hybrids that give back to the grid

Additional equipment is needed to make a plug-in hybrid into a vehicle-to-grid machine. This piece of equipment reverses the charge stored in the batteries to send it back to the wall and to the electrical grid, where it could be used to power a house in an emergency. It also takes up a fair amount of space in the trunk.

Photo by Tom Krazit/CNET News.com