The first Toyota Prius plug-in hybrids (PHV) in the UK have joined the fleets of five businesses and public organisations on three-year leases where, Toyota GB said, “they will demonstrate the fuel efficiency, low emissions, cost savings and everyday practicality their rechargeable hybrid power system can deliver”.

“The real-world experiences of the drivers and fleet operators will provide both companies and UK government with valuable insights into driver attitudes and usage patterns to help them design their strategies for introducing plug-in hybrids and recharging technologies. It will also help inform and shape public policy in this field,” the automaker added at a launch event in London today.

Electricity supplier EDF Energy’s charging infrastructure will help monitor usage.

As with pure electrics, the PHV test programme has government help: the lease programme is part of the Technology Strategy Board’s Ultra Low Carbon Vehicle Demonstrator Programme and the coalition’s Office for Low Emission Vehicles (OLEV) is providing the cash.

Organisations and businesses using the cars are Transport for London (the red bus, Tube and train operator), the government’s Car and Despatch Agency, the Metropolitan Police Service, Times and Sun newspaper publisher News International and satellite TV company Sky.

The cars are modified third-generation Prius hybrids with a lithium-ion battery (in place of nickel metal hydride) recharged by a standard 240V electricity supply.

EDF Energy has set plug, socket, wiring and cabling specifications to comply with BS7671 safety standards while maintaining ease of use. The charging points have a keypad that enables each user and vehicle to be identified when recharging.

The rechargeable battery gives the PHEV an extended range in EV (electric vehicle) mode of up to 12.5 miles (versus the mile or so just-auto has achieved in the standard hybrid) at speeds up to 62mph (100km/h; the regular car only gets up to about 50km/h or 30mph before the petrol engine joins in). Toyota reckons the PHEV version can therefore do “most” urban journeys with zero fuel consumption and tailpipe emissions. Combined cycle fuel consumption and CO2 emissions are 108.6mpg and 59g/km.

Although there is usually a vast gap between the standard car’s 72.43mpg official combined EU test score and owners’ real-world experience (late 40s, early 50s, depending on driving style and conditions, according to owners we’ve asked), that is nonetheless a significant improvement.

If the battery runs down in the PHV version, the petrol engine cuts in to recharge it and move the car, just as in the standard model. That means no “range anxiety” about the distance his or her car might manage, Toyota said.

The UK test fleet is part of 200 in Europe and 600 world wide. As to wider availability, Toyota continued to say only it would launch a PHV “within the next few years”.

Rob Golding’s view here