If you're in the market for a new (or used) car, you might want to consider a 'green' car to reduce your impact on the environment ... and your budget.

Cars are a major cause of air pollution in urban areas, producing harmful substances such as carbon monoxide, nitrogen oxides and hydrocarbons. Road traffic is responsible for about 13% of Australia's greenhouse gas emissions.

Although more of us are getting on board with walking and cycling, not everyone is ready to give up their wheels completely. Luckily there are cars available that have less impact on the environment than the standard gas guzzler.

Spend less at the servo

With fuel prices on the rise, a fuel-efficient car means more money in your pocket. But if you're looking to save money overall, you'll need to do your homework (and some maths), as the purchase cost of the car might cancel out any savings at the bowser. If you're keen on being kinder to the environment, some technologies will be better at this than others.

Fuel-efficient petrol, hybrid and electric cars

The fuel-efficient petrol, hybrid and electric cars available in Australia are easy to drive and use less fuel than comparable conventional models. They burn less oil and emit less pollution and greenhouse gases. However, these cars cost more than their standard equivalents, so you'll need to drive them for many years before you recover the difference.

Fuel-efficient petrol cars

Car manufacturers can use a number of new technologies to make petrol-run cars more efficient without resorting to battery technology. These include:

  • guidance mechanisms for more efficient gear changing
  • automatic gearing that makes the best use of gear ratio
  • engine-off mechanism that turns off the engine when the car stops at lights
  • braking systems that feed energy back into the car battery
  • low profile tyres to make rolling resistance more efficient
  • lighter body weight meaning better fuel efficiency
  • engines that are more efficient and use lighter materials.

Examples of car models that use these technologies include the Mazda SkyActiv and VW BlueMotion.

Hybrid cars

Hybrid cars use a combination of battery technology (electric engine) and a petrol engine. There are four main technologies available at the moment:

Power split or series parallel hybrid – the electric engine can power the car on its own. Examples include the Toyota Prius, Toyota Camry and Toyota Prius C.

Parallel hybrid – the electric engine assists the petrol engine when it's moving. Examples include the Honda CR-Z, Honda Civic Hybrid, and Honda Insight.

Series hybrid – mostly runs on battery, and the petrol engine recharges the battery. Currently the only series hybrid in Australia is the Holden Volt.

Plug-in hybrids – supplement energy generation by charging from the power grid, however these are not yet common in Australia. How 'green' these cars are depends on where the car owner sources their electricity (coal fired or a green energy source).

Electric cars

An electric car is powered by an electric engine and battery. Recently introduced in Australia, there is a very slow uptake of these types of vehicles because:

  • they are more expensive than a petrol-fuelled car
  • of 'range anxiety' (concerns about not being able to go longer distances)
  • there are fewer recharging stations compared with petrol stations
  • of the cost to replace battery.

These drawbacks may become less of a concern as infrastructure increases and battery prices come down. With better battery technology, range anxiety will also probably decrease, and if electric cars become more mainstream their price will become more competitive. There are currently a few types of electric cars in Australia such as the Mitsubishi i-Miev and Nissan Leaf. There are others slated for release in future.

A current advantage of the electric car is the lack of moving parts compared to a petrol engine vehicle, which should make it cheaper to service the car. As per the plug-in hybrids above, how "green" these cars are depends on how green the electricity source is.

Other things to consider

Different fuel types – petrol, diesel or LPG?

A litre of LPG contains less energy than a litre of petrol, so LPG consumption per 100km is higher than petrol consumption for models that have LPG and petrol versions. However, it burns a lot cleaner than petrol, so emissions are lower.

Cars that run on diesel are usually more fuel-efficient than petrol versions of the same model. However, they produce particulate matter and higher levels of nitrogen oxides.

Fuel consumption of hybrid cars

Size-wise (not engine-wise; the point of hybrids is that they have smaller petrol engines) Toyota compares the hybrid Prius to its regular Camry. In tests carried out for the Australian Green Vehicle Guide, the fuel consumption in the standard combined city/highway test cycle for the Prius was just 3.9L/100km; the automatic 2.5L version of the Camry uses 7.8L/100km. The Honda Civic Hybrid uses 4.4L/100km, and the comparable non-hybrid Honda Civic, the manual Si sedan, uses 6.9L/100km.

So one thing is clear – if you drive a hybrid you'll be filling up less often.

A hybrid car may not save you money

Petrol is not (yet) quite expensive enough to make a hybrid the accountant's vehicle of choice. With petrol at $1.50/L, and based on travelling 15,000km/year and the above consumption figures, it would take many years to gain back the difference in purchase prices between the base Prius and the Camry. Ditto for the Honda. But that's assuming petrol prices won't rise!

Emissions

Hybrids emit much less greenhouse gas than most standard petrol cars. The main greenhouse gas from cars is carbon dioxide, which is directly related to the amount of fuel used. An Australian study that included the Prius and some experimental hybrids estimated they produced 66% less carbon dioxide than the average Australian family car.

The Green Vehicle Guide rates the Prius at 9 out of 10 for greenhouse gas emissions and the Civic Hybrid at 8.5. As a comparison, the non-hybrid Civic scores a 7, the Camry a 6.5.

When it comes to electric vehicles, the big advantage for environmentally-conscious drivers is the lack of emissions from the non-existent tailpipe. There will be indirect emissions, however, related to the electricity source that powers the battery.

Which is greenest?

If your goal is zero emissions, the greenest set of wheels you can drive (other than a bicycle) is an electric car charged with solar electricity, or any other low-carbon power source such as wind or hydro.

Charging an electric car with electricity generated from coal or oil means carbon emissions are still being generated (in somebody else's backyard) and the impact on the environment is likely to be greater than that of a hybrid or fuel-efficient petrol car.

Hybrids are a greener option than petrol cars, because the better the fuel efficiency, the lower the emissions.

Cost

Electric cars cost upwards of $50,000
Hybrid cars cost upwards of $25,000
Fuel-efficient petrol cars cost upwards of $15,000