Carmakers' plug-in plans

Priuses are sometimes modified by other companies for use as plug-in hybrids but, for safety reasons, Toyota doesn't sanction those conversions.

Late last year, Toyota presented its own plug-in Prius to the University of California campuses at Berkeley and Irvine.

Based on current-generation Toyota Priuses, the cars have oversized nickel-metal hydride batteries rather than more expensive lithium-ion batteries used in many other plug-in hybrids.

On a full charge, the Prius plug-in can drive up to seven miles on electric power alone at speeds up to about 62 miles an hour, according to Toyota.

Toyota has said it intends to bring some sort of plug-in hybrid to market in 2010, at about the same time that GM plans to bring its two types of plug-ins.

NEXT: Toyota 1/X concept