Jo Lauder
We've lined up an electric and a petrol car and put them to the test.(ABC News)

Whether you drive an electric car or are considering making the switch, you've probably been drawn into a discussion about whether they are really better for the climate.

Electric cars are key to the world reducing emissions, with transport accounting for almost 20 per cent and rising, so you probably haven't had that debate for the last time.

To save you from your next barbecue encounter, we have turned to the EV Council, which has crunched the numbers for you.

We're comparing an electric car and a traditional petrol one and looking at the life-cycle emissions — that is, all the emissions produced from cradle to grave.

For both types of car, these are the key stages where emissions are produced:

  • manufacturing of the car,
  • production of the battery, especially for electric cars
  • running the cars over their life-cycle, either on petrol or electricity
  • disposal and recycling of the vehicle at the end of its life, including batteries

We'll also compare electric cars in different states because each state uses different amounts of fossil fuels for electricity, which affects how "clean" the car is.

To compare cars, we've chosen an average medium SUV, the sort of car you commonly see on Australian roads.

Some examples of a medium SUV are the electric Tesla Model Y, Toyota's RAV4 and the Mazda CX-5 on the petrol side.

So, buckle up and let's go.

Let's start at when the car is made

Manufacturing covers the production of the raw materials in the car's metal body, interiors, tyres, seating, the whole bundle. At this first stage, all these cars come out with similar emissions profiles.

… adding batteries for EVs

Battery production is the stage where we start to see a split between petrol and electric cars.

Electric vehicles (EV) are powered by batteries, so their batteries are significantly larger and heavier, and use more critical minerals. Our electric SUV also needs a bigger battery than a small hatchback.

It's important to note that this is about life-cycle emissions, so we aren't evaluating other environmental or human rights impacts from battery production for EVs, and we're also not critiquing the oil industry in those areas for petrol cars. That barbecue debate is for another day.

Batteries produced in China have higher emissions than those produced in Europe, and as most Australian electric cars currently have Chinese-made batteries, that's what's used here.

Climate experts and even the latest Intergovernmental Panel on Climate Change expect these figures to drop as more renewable energy is used in the coming years to make the batteries.

"So the energy needed to produce batteries is decarbonised, and therefore has lower emissions," according to University of Technology Sydney transport researcher, Robin Smit.

So at this point, before the cars hit the road, electric cars have more embedded emissions.

But that all changes when you start driving …

Taking our cars on the road

It won't shock you to find out that most of a car's lifetime emissions come from powering it to drive.

"The fuel energy cycle is normally the most important part of the life-cycle assessment [and] that includes on-road driving, the maintenance, and of course, the production of the energy," Professor Smit said.

The Australian Bureau of Statistics (ABS) estimates the average Australian car drives about 12,600 kilometres a year, or 189,000 over its lifetime, so that is what's used in this modelling.

Petrol cars are dirty. That's a fact. Combustion cars are powered by burning petrol, which releases emissions into the atmosphere and is — pardon the pun — a major climate change driver. These are referred to as "tailpipe emissions".

The petrol SUV here is up against an electric SUV charged on the national grid, which has a mix of fossil fuels and renewables.

Our petrol SUV produces almost 46 tonnes of carbon over its lifetime on the road.

These figures also factor in the emissions coming from refining and transporting the fuel.

"When you look at fossil fuels, they need to be extracted, processed, and then transported to service stations, for example, to make them available. So there's a greenhouse gas emission costs associated with that," Professor Smit said.

The estimated petrol used here is 8.3 litres for 100km and comes from the Worldwide Harmonised Light Vehicle Test Procedure (WLTP). These figures are almost always lower than real-world petrol use.

So, a lot of energy is burnt to move petrol cars, but most of it is wasted.

"They are not efficient, about 70 to 80 per cent of the energy is wasted in heat. So you only use 20 to 30 per cent of the energy into fuels for actually driving around," Professor Smit said.

What's more, Australians typically drive heavier cars than other countries, especially in Europe. Heavier cars require more fuel to move them, resulting in higher emissions.

This all means that petrol cars start producing significantly more emissions during their use, leaving electric cars in the dust.

Let's look at a different view of our two cars as we drive them for 15 years or 189,000km. Petrol cars are displayed in the blue line, and electric cars in red.

Electric cars are powered by electricity (obviously!) but how that electricity is created makes a huge difference to the overall emissions profile of EVs.

Strap in.

You can see emissions for the petrol car rise while the electric car's life-cycle emissions curve is flattening. That's because the composition of our electricity grid is rapidly changing and more renewables are coming online.

To account for that, this modelling from the EV Council uses the scenario mapped out by the Australian Energy Market Operator (AEMO) which predicts the rate of new renewables coming into the grid and fossil fuel plants being decommissioned. That is, by 2030, the same electric car will be producing lower emissions because it will be charged with more renewable power.

So this is for Australia as a whole, but where you live can also have a big impact on how much cleaner an EV is.

Some Australian states already have mostly renewable energy powering their grids, while others still have lots of fossil fuels.

A car that's charged off a grid with lots of fossil fuels produces much higher emissions than a car charged somewhere with mostly renewable energy.

Let's look at our electric SUV in Western Australia, where in 2022 more than 83 per cent of electricity came from fossil fuels, mostly gas.

Now this is what our SUV's emissions look like in Tasmania (shown in the green line), which powers almost its entire electricity network on hydro.

It's the same in South Australia, which has lots of wind and solar energy in the grid. You can see here that no matter where the EV is, it saves tonnes of emissions overall compared to a petrol SUV.

This highlights the huge opportunity to reduce transport emissions with electric cars.

The cleaner the grid, the cleaner the electric car.

What about cars charged on rooftop solar?

More than 3 million Australian homes have rooftop solar and, according to a 2021 survey, most EV owners plug into their own set-up.

A car that's charged with rooftop solar produces even lower emissions over its lifetime.

"When you use solar panels, they basically have very small-to-negligible emissions," Professor Smit noted.

Less than a tonne of carbon over all those kilometres!

Now, it's time to say goodbye to our cars and send them to the car afterlife …

Getting rid of our cars

According to Professor Smit, the greenhouse gas emissions from taking cars off the road are small compared to the overall driving life of a car.

What's more, most of the materials in a car can be recycled, so this offsets some of the emissions from the production of the car at the start of the cycle.

To complete our emission profile, let's add the emissions for the disposal of our cars.

There's a lot of potential for improvements here too.

It takes a lot of grunt to power a car, and when a battery can no longer do that and comes out of an electric car, it still holds a lot of value and charging potential.

It can be used as a backup household battery, for example. Some car companies like Tesla are already using old car batteries to power their factories.

It's estimated this second life for EV batteries could cut the carbon footprint of battery production by half.

At the finish line

Overall, every electric car will produce fewer emissions than its petrol equivalent, no matter where they are charged.

Even with an electricity grid that still uses some fossil fuels, electric cars have much lower overall carbon emissions, and that will continue to drop as the electricity gets greener.

And remember, this example uses SUVs, so lighter electric cars like hatchbacks have even lower emissions.

Hang on, what about hybrids?

Put simply, hybrids are complicated.

Plug-in hybrids can be run off either petrol or from a battery that's plugged in and charged. Therefore, the life-cycle emissions from a plug-in hybrid depend on the region where it gets charged but also on how diligent the driver is with charging. Remember, it can also run on petrol.

The European Union's Environment Agency recently found that emissions from plug-in hybrids were 3.5 times higher than reported.

It concluded that hybrids "are charged and driven in electric mode much less than how they were expected to be used".

Where we get our figures from

These figures come from the Electric Vehicle Council, which based its life-cycle emissions calculator on modelling from the European organisation Transport & Environment.

We got Professor Smit to look over the EV Council's modelling and he said while it was generous to petrol cars, it provided a good way to compare life-cycle emissions.

The inputs for petrol use are based on the WLTP. As mentioned in the story, this is likely to underestimate real-world petrol usage.

The modelling uses data for a Nickel-Mangenese-Cobalt NMC li-ion battery produced in China, as that's the most common type of battery in the Australian EV market.

It calculates 105kg CO2/KWh for the carbon produced from battery production.

This same study found that "producing batteries with photovoltaic electricity instead of Chinese coal-based electricity decreases climate impacts of battery production by 69 per cent". Considering this estimate would reduce the emissions calculation in the point we make about battery production.

For a medium electric SUV, the energy used is 17.3 KWh/100km and a battery size of 70.2 KWh average for cars available in that category.

The emissions factors for energy sources are based on data from the Intergovernmental Panel for Climate Change here. 

To model the rate of renewables coming into the grid, the EV Council used the step-change scenario from the AEMO.

Statements about the composition of the electricity grids in different states come from 2022 numbers from the Department of Climate Change, Energy, the Environment and Water.

The estimate of recycling emissions comes from a study by Transport & Environment.