Toyota will introduce a plug-in version of its Prius hybrid model some time after the third generation model is launched but the technology will probably be optional in Europe, a senior Toyota official told just-auto on Tuesday night.

"The plug-in will arrive during the life of the third generation model," Toyota Motor Europe executive vice president and chief operating officer Thierry Dombreval said at a media dinner on the eve of the Tokyo motor show. He hinted that the new generation was two to three years away with the plug-in possible by 2011.

He added that the plug-in technology would "most likely" be an option in Europe where many owners lack garages or even off-street parking and therefore have no access to exterior mains electricity for recharging.

"Having to go to a plug-in station would undermine the model's credibility," Dombreval said.

He said the price premium for the plug-in model was still not decided and would not confirm or deny various price points such as EUR1,000 suggested to him.

Earlier in the day, a group of UK and European journalists had the chance to try the plug-in prototypes on a closed circuit at Toyota's Higashi-Fuji Technical Centre.

From the outside, decals apart, the PHEV or Plug-in Hybrid Electric Vehicle version, as it is officially known, looks no different from the regular hybrid model, apart from an additional fuel filler flap, this time on the right-hand side. This opens to reveal a circular multi-pin plug that takes a connector cable from the mains, much like you'd hook up a caravan/RV to a mains supply.

Whereas the standard hybrid Prius will run solely on electric power for less than a kilometre, at low speeds only, before the petrol engine kicks in, this one can run for up to 10km, thanks to a larger battery, modified control electronics and other changes. The boot (trunk) floor is higher and there is no storage space or spare wheel - or access - on the prototypes so guess where the extra battery goes.

If you're used to a standard Prius, you instinctively know at what point under which conditions the petrol engine will start, so it's uncanny to reach 70km/h/40mph (a maximum imposed by the engineer/minder in the passenger seat) and realise you're still all-electric. The quietness is notable. When the petrol engine is switched in, manually in the test car's case, there's a rise in power and noise to the same level as the production Prius.

The idea is that you can use mains electricity to do short commuting more cheaply than the solely petrol-electric hybrid but when the battery runs down, the petrol engine starts recharging it and you drive on, rather than having to stop and wait hours for another mains recharge. When it's convenient, you can park up and use the mains to top the battery back up to maximum charge.

Based on US and Japanese market experience with all-electric models like a version of the first-generation RAV-4, the need for specialised recharging stations and the length of time for recharging limited their market appeal, Yokita Asakura of Toyota's hybrid vehicle engineering division said.

"We believe that a pure EV is suitable only as a small vehicle or short-range driving vehicle," he said.

"So we aimed to develop a system that can offer both the merits of biofuels and electric vehicles."

That's the PHEV.

Dombreval, meanwhile, reckons the standard Prius has still to reach its full potential in Europe.

"There's still a relatively small number of people in the know," he said.

He added that the car had become "the darling of Milan's taxi drivers" because they could get the same fuel economy as a diesel yet use the electrically-powered air conditioner while parked, engine off, waiting for the next fare. Passenger load space, luggage area and the ability to dodge vehicle-use restrictions on high pollution days were also a plus, he noted.

The Prius is also accounting for 10% of Toyota's volume in Sweden - its highest penetration anywhere.

Graeme Roberts