Toyota is getting ready for a limited run of a plug-in Prius, which can average 100 miles per gallon, for use in government and commercial fleets starting in 2009. Toyota will monitor how these cars, which will have high efficiency lithium ion batteries that haven’t been fully tested yet, will hold up under everyday use.  Whether or not these will ever be released to the public will depend on how well the vehicles perform and how reliable they are.

A plug-in version of the Prius is different from the current Prius in that the regular Prius relies more on its gas engine, switching to (or combining) use of the electric motor in slow traffic, to maintain cruising speed, and when idling or backing up.  Its battery is charged by the motion of the wheels and brakes and the gas motor. The plug-in, on the other hand, will primarily use its electric motor, allowing commuters to travel much farther on the electric charge, saving the gas engine for longer trips that exceed the distance the car can go on electricity alone.

It could take many more years for production plug-in hybrids to reach mainstream garages in America, but there is a quicker alternative. There are some DIY plug-in kits for consumers that already have Prius, although the kit is mostly not a do-it-yourself affair. A buyer will have to take his Prius to one of six authorized installation centers spread across the country.  Installation is included in the purchase price.  Another concern is that the conversion may put the warranty in jeopardy, so this should be done with caution.  Since hybrid cars typically have four or five separate warranties, the modifications may not completely void warranties—only the part(s) affected by a retrofit.  An important note: this conversion is not a cost saving action; it would take years to start saving money, considering the cost of the DIY kit.  Still, for many consumers out there, the purpose of doing this conversion for the sake of the environment is well worth it.