Part of a Europe-wide programme, the London trial involved leasing 20 Plug-In versions of the third generation Prius to businesses in the capital, monitoring usage, vehicle performance and drivers’ recharging patterns.

Conducted in a partnership with EDF Energy, the results will inform final development of the production Plug-In Prius due in 2012 and EDF’s future EcoRecharge timer-based off-peak charging points.

Largely similar to a conventional Prius, the Plug-In version has a lithium ion battery pack which can be recharged from a mains electricity supply, like a pure electric car. It gives a range of 12.5 miles at speeds of up to 62mph, after which time the Prius switches seamlessly back to running like the hybrid on which it is based.

The results have shown an average journey of 7.3 miles, with 59% of all trips falling between 3.1 and 12.4 miles. Drivers were travelling at an average speed of 17.7mph, and 69% of journeys averaged less than 18.6mph, well within its full electric capability.

Toyota said it shows the Plug-In Prius is well-suited to urban driving, recording 27% better fuel economy than an equivalent sized diesel car but without the range anxiety of pure electric cars. Fleets taking part in the study said they rated its ability to cover longer distances when needed.

The cars are part of a fleet of 200 Plug-In Prius models on trial around Europe, and results are similarly encouraging for the rest of the vehicles. Europe-wide, the average journey covers 8.2 miles, with two thirds covering less than 12.5.

A third of all driving is taking place in full EV mode, with 22% covering more than 12.5 miles before exhausting the lithium ion batteries. As a result, Europe-wide average fuel economy was 36% better than the best-in-class diesel, and 49% better than the best-in-class petrol.