There is interest in efficient cars including the latest 'green' or low greenhouse gas emitting vehicles that are available on the market. These cars offer fuel savings and, with increasing concerns over the link between carbon dioxide emissions and climate change, are an environmentally sensitive alternative.

So what should you look for when considering a green car? In the last few years, Australia has fallen into line with European Union emissions rules. The upcoming standard, called Euro V, applies to all new models introduced from 2013 and all new cars on the market from 2016, according to the Third Edition of the Australian Design Rules. An even more stringent rule, Euro VI, comes into force in 2017 according to the Australian Design Rule number 79.

Euro standards are important because they provide an international benchmark for the cleanliness and efficiency of modern cars. However the locally-published, Federal Government-approved Green Vehicle Guide is a great reference for new car buyers wanting to compare how clean their potential purchase is likely to be.

The Guide lists top-ranked cars for tailpipe emissions in both outright performance and in terms of overall sales. Unsurprisingly, the top performers for overall tailpipe emissions are the cars that don’t produce any at all! These include the totally electric-powered Mitsubishi I MiEV, ranked number one, and the sporty Tesla Roadster, ranked number two. Nevertheless both are expensive in comparison to conventional petrol cars. The Mitsubishi has a price approaching $50,000, which is pricey for a small hatch, while the Tesla is Porsche-expensive, at over $200,000.

Tesla Roadster: top performer for overall tailpipe emission. Source: Tesla

More affordable, and still attaining a five-star performance rating in the Green Vehicle Guide are the hybrid cars. These combine a petrol engine with an electric motor, offering a degree of emissions-free motoring without the “range anxiety” that comes from using a purely battery powered car.

The top ranked hybrids in terms of their tailpipe emissions are cousins under the skin – the Toyota Prius and the Lexus CT200h. Honda’s Insight, which uses a different hybrid system, comes in at number six in the overall top environmental performance ladder, beaten by the diminutive, petrol-powered smart fortwo, which isn’t a hybrid at all.

The Toyota Pruis: environmentally friendly hybrid car. Source: Toyota

But what of the top selling cars in Australia? The number one selling vehicle in September 2011 according to VFACTS , the Toyota Corolla, earns a three and a half star ranking for its environmental efficiency, while the Australian-manufactured Holden Commodore, Australia’s number two car, according to VFACTS, and the best-selling large car, earns a solid four environmental stars (the best rating is five), making it a good performer given its size and popularity in the market.

The Guide also makes it easy to compare vehicles using a series of drop down menus. In the showroom, shoppers can rely on the stickers on the windscreen to see the average fuel economy of the vehicle, and its tailpipe emissions in terms of grams of carbon dioxide emitted per kilometre, measured by the Australian Design Rule.

Also of interest to green vehicle buyers is the forthcoming carbon tax, however, this is of less concern to private car drivers than those from business. According to the Federal Government, households and on-road commercial vehicles of less than 4.5 tonnes will continue to only pay the current fuel excise, with fuel for these vehicles not directly affected by the carbon tax‎.