Comparing car efficiency and emissions

When you're choosing a car, efficiency figures help you compare running costs and emissions across very different vehicles: a small petrol hatch, a hybrid SUV, a plug-in hybrid ute and a battery electric sedan. The trick is to use consistent, official figures and to understand what they do and don't tell you. In Australia, the Green Vehicle Guide is the place to start. This guide explains how to use it and how the New Vehicle Efficiency Standard fits in.

What the Green Vehicle Guide is

The Australian Government describes the Green Vehicle Guide as Australia's official national guide to vehicle fuel consumption and environmental performance. The redeveloped site launched in July 2022 after research found people didn't know where to look for information on fuel-efficient and electric vehicles. It covers both new and used vehicles.

Its main tools are:

• Search and compare: compare fuel costs and environmental impacts of the cars on your shortlist.
• Fuel and CO2 calculator: estimate total annual fuel costs and CO2 emissions.
• Home charging calculator: estimate EV charging time and costs.
• Fuel lifecycle emissions: see a vehicle's emissions over the full fuel cycle.
• Top 20 performers: see the top performing and top selling vehicles.
• Vehicle guides: information on electric, hybrid and hydrogen vehicles.

Reading the figures

The Green Vehicle Guide's search shows emissions, fuel consumption, electric range, cost and noise data for each vehicle. It points out that cars of the same make and model can produce different emissions and use different amounts of fuel depending on the body type, engine, transmission and drivetrain, so you need to pick the exact variant.

Key figures to understand:

• Fuel consumption (L/100 km): litres of fuel used to travel 100 km in the standard test. Lower is better. Often shown for combined, urban and extra-urban cycles.
• Energy consumption (Wh/km or kWh/100 km): for EVs and plug-in hybrids on electric power. Lower is better.
• Tailpipe CO2 (g/km): grams of carbon dioxide from the exhaust per kilometre. Battery EVs have zero tailpipe emissions.
• Electric range (km): the estimated distance on electricity for EVs and plug-in hybrids.
• Fuel lifecycle emissions: emissions from producing and supplying the fuel or electricity, as well as using it. This gives a fuller comparison between fuel types.
• Noise: some vehicles list stationary noise data.

Why official figures differ from your experience

Official figures come from a standardised laboratory test, so every car is measured the same way. That makes them excellent for comparing cars, but your own results will differ. The Green Vehicle Guide's own guidance notes that on-road consumption is affected by individual circumstances. Speed, traffic, terrain, load, air conditioning, weather, tyre pressures and driving style all play a part. Our fuel-efficient driving tips explain how much difference some of these make.

Use the official numbers to rank cars against each other, then think about how your own driving might shift them. A hybrid's advantage, for example, is usually biggest in stop-start city driving.

A practical comparison method

1. Shortlist by need first: seats, boot space, towing, safety rating, budget.
2. Find each exact variant on the Green Vehicle Guide.
3. Compare fuel or energy consumption and tailpipe CO2.
4. Estimate annual energy costs with the fuel and CO2 calculator or your own numbers: annual distance × consumption × your price.
5. Check lifecycle emissions if you're comparing fuel types.
6. Add other costs such as servicing, insurance and registration. Our guide to EV running costs includes a worksheet.

Comparing across fuel types

Comparing an EV with a petrol car means comparing kWh with litres. The cleanest way is to convert both to a cost per kilometre with your own prices: for the EV, energy use × your electricity rate; for the petrol car, fuel use × your fuel price. For emissions, the Green Vehicle Guide's lifecycle figures account for how the fuel or electricity is produced.

For plug-in hybrids, both figures matter. The official combined figure assumes a certain mix of electric and fuel driving. Your real mix depends on how far you drive between charges and how often you plug in.

The New Vehicle Efficiency Standard

The New Vehicle Efficiency Standard (NVES) is a newer part of the picture. The Department of Infrastructure says it commenced on 1 January 2025 and applies to new cars supplied to Australia from that date, with the first reporting period beginning on 1 July 2025. The NVES Regulator says it sets carbon dioxide emissions targets for new passenger cars and light commercial vehicles, such as utes and vans, entering the Australian market from 1 July 2025, and applies to new passenger and light commercial vehicles up to 4.5 tonnes gross vehicle mass.

What it means for you as a buyer:

• It applies to suppliers, not drivers. Car makers and importers are the regulated entities, not people who buy or drive cars.
• It doesn't affect cars already on the road. The NVES Regulator says vehicles registered on the Register of Approved Vehicles before 1 July 2025 aren't covered.
• Its aim is more choice of efficient vehicles. The government introduced the NVES to encourage more lower-emissions vehicles on Australian roads.

The detailed rules, such as how targets and credits work, are set out on the NVES Regulator and Department of Infrastructure websites.

Other things worth comparing

Efficiency is only one part of a good choice. Also check:

• safety ratings from ANCAP;
• fit for purpose: size, practicality, towing capacity;
• warranty, including battery warranty for EVs and hybrids;
• servicing costs and intervals;
• charging access if you're considering an EV or plug-in hybrid.

Used cars

The Green Vehicle Guide includes used vehicles too, so you can look up the official figures for an older car you're considering. Keep in mind the car's age, condition and, for EVs and hybrids, battery health. See buying a used electric car.

Keep a record of your shortlist

Write down the exact variant, official fuel or energy use, CO2 figure and your estimated annual cost for each car. Having the numbers side by side makes test drives and negotiations easier.

Key points

• The Green Vehicle Guide is Australia's official guide to vehicle fuel use and emissions.
• Choose the exact variant, as engine and drivetrain change the figures.
• Use official figures to rank cars, then adjust for your own driving.
• Compare across fuel types with cost per km and lifecycle emissions.
• The NVES, from 2025, sets CO2 targets for suppliers of new light vehicles, not drivers.