This was a bit of a one-sided fight, because the Prius hybrid has the used green market in the bag. The sheer number for sale means it's not too expensive, despite holding its value better than most cars, and the shortage of serious rivals makes it your best bet when seeking a used green car.
That's not to say that its rivals aren't worth considering, but cars such as the Honda Civic Hybrid ('06-'09) just don't give you the same everyday usability for similar money.
The Prius is at home in cities and towns, because it's nippy and agile, and its hybrid technology saves fuel when you're stuck in traffic or waiting at junctions. At low speeds, the electric motor means the car runs silently and with zero emissions, while the 1.5-litre petrol engine cuts in to boost performance or top up the on-board batteries.
Its smooth ride irons out most urban bumps and lumps, but it's also capable on faster roads, with sure-footed handling.
Inside, there's plenty of room for four adults, and although the boot space isn't massive, you can fold down the rear seats for larger items. Our favourite trim is the T3, which comes with electric windows all round, a CD player and climate control.
As good as the Prius is, though, the market for used green cars looks set to grow. Efficient new models from BMW, Ford, Toyota and Volkswagen mean there's going to be a wider choice for the environmentally responsible used car buyer in the future.
Buyer's Guide Power 76bhp Fuel Economy 65.7mpg (average) 0-60mph/Max 11.5sec/102mph Insurance Group 7 CO2 Emissions 104g/km Road tax £35 a year euro NCAP rating 5 star Reliability rating 4 star Service intervals 10,000 miles
VW Polo 1.4 TDI Bluemotion Fuel economy 74.3mpg CO2 emissions 99g/km Road TAX na
BMW 320d Fuel economy 58.9mpg CO2 emissions 128g/km Road tax £120
Ford Focus 1.6 TDCi Econetic Fuel economy 65.6mpg CO2 emissions 115g/km Road tax £35
Mini Cooper 1.6D Fuel economy 68.9mpg CO2 emissions 109g/km Road tax £35