With the longer electric vehicle range and greater battery capacity of the plug-in Prius, regenerative braking, engine braking and excess petrol engine output alone aren't enough to recharge the batteries.
A standard electric vehicle charging port allows the plug-in Prius to be fully recharged from mains power in about 100 minutes.
The up-rated batteries, larger radiator, power point and battery charger under the driver's seat (pictured) add 135kg to the Prius' weight — three-quarters of that difference is thanks to the Lithium-ion battery pack. Toyota has revised suspension, but not the brakes, to cope with the extra weight.
As far as the ride and handling are concerned, the most obvious thing we could discern from our brief 4-kilometre drive was that the steering felt considerably heavier. Moving off from standstill there was only a small amount of electric engine whine — pretty much the same as a regular Prius.
So long as you don't think you're Craig Lowndes, the plug-in Prius will remain electrically propelled at speeds of up to 100km/h — on a normal Prius, the petrol engine cuts in at around 30 or 35km/h. At speeds greater than 30km/h, the eerie electric silence disappears, replaced by the gentle rumble of the tyres.
For the plug-in version, Toyota has junked the EV Mode button because the car naturally defaults to electric power. Floor the gas pedal, though, and the unmistakable drone of the Prius' petrol engine is clearly audible.
There's a revised in-dash energy monitor that can display remaining electric vehicle distance, time to full charge and electric/hybrid driving ratio.
Also present is a new air-con system that's designed specifically for cars operating primarily in electric vehicle mode. The new system can cool and heat the Prius remotely — the standard Prius' remote air-con can only cool the car. There's also a humidity sensor that allows the air conditioner to change automatically between ventilation and recirculation modes.
Sorry, it's not for sale. Toyota is hoping to have a plug-in hybrid available in the US and Japan by mid-2012, though. The plug-in Prius we drove is one of only 600 in the world and was produced as part of a worldwide trial of the technology.
Five cars have been allocated for Australia, with one already earmarked for trials with the Victorian Government.