Is a diesel cleaner than an electric car in Australia? | The Driven

“My diesel dual cab is cleaner than electric vehicles”, said one of my drinking companions proudly. “Because in Australia electric cars are powered by electricity generated from coal.”

A couple of others nodded wisely while I just stared into my beer.

My friends decided that because of my unsupported pro electric car nonsense I should buy the next round.

This conversation occurred 18 months ago and although it didn’t seem right, I didn’t have the all the facts at hand – or even a very clear head!

It is a fact, however, that in Australia most of our electricity is currently supplied from coal fired power stations – but does this necessarily mean electric cars are worse for the environment?

By having a look at two important factors that differentiate electric cars from conventional vehicles we can learn which is the cleaner choice.

These two factors are firstly; the vehicles’ motor efficiency, and secondly; the energy source that drives each type of car.

Fossil fuels of course power internal combustion vehicles; while the electrical grid powers most Electric Vehicles (EVs).

Health benefits from electric cars’ zero emissions are another important issue but will be a matter for another article.

What follows will hopefully shed some light on the key differences between conventional and electric cars and provide an answer as to which is cleaner.

1 – Motor Efficiency

Internal Combustion Engine Motor Efficiency

Many people complain that their car does not achieve anything like its rated fuel efficiency.

Far fewer realise that even if their car matched its official rating, petrol and diesel cars are very inefficient in converting the energy in their tanks into motion at the wheel.

How inefficient are they? For diesels the efficiency average is approximately 25% and for petrol engines the average is closer to 20%, according to Queensland academics, Whitehead, Smit and Robinson. 1

A large number of other studies worldwide have achieved similar results. They all prove internal combustion engines are just not very efficient. So, where does the rest of this energy go?

“Over 60% of the energy is wasted as heat”, states John Cuprisin, Associate Professor Automotive Technology at Pennsylvania College of Technology.2

An amusing form of proof of this wasted heat is easy to find all over the world in cooler climates when you see cats lounging comfortably on the bonnets of ICE (Internal Combustion Engine) vehicles that are still warm hours after they have been switched off.

There is more to this story than wasted heat however.

Beyond burning the fuel in your tank, if you take into account the energy used getting the fuel out of the ground, shipped, refined and transported to the fuel station petrol and diesel efficiency figures drop lower again.

Electric Vehicle Motor Efficiency

By comparison the drivetrain efficiency of electric vehicles means that between 80% – 90% of the energy stored in the battery drives the car forward. 3

Electric cars waste little of their available energy as heat primarily due to the efficiency of electric motors.

This means that an electric car such as the new Tesla Model 3 SR+ can travel with an EPA accredited range of 400km from a battery just over 50kWh in capacity.

To place this energy efficiency into perspective, one litre of petrol contains very close to 10kwH of energy. In a petrol-powered car if there were just 5 litres of fuel left in the tank (50 kWh) drivers would be looking for a service station to fill up – not travel close to 400km.

If you think of a petrol-powered car with a 50lt tank and a typical urban range of 600km, as carrying the equivalent of 500 kWh of energy, you realise how much energy is burned and wasted as heat in normal use.

Additionally, as further proof of the absence of wasted heat energy, a scouring of the internet fails to find any pictures of cats snoozing on the bonnets, or any other parts, of electric cars!

2 – The Energy Source

In examining which technology is cleaner you can’t look at the issue of motor efficiency alone.

Electricity sitting in a battery has to be generated by some means and transferred to the EV battery (with resultant losses along the way) while fossil fuels have to be taken from the ground and go through the processes of transportation and refinement to eventually end up in your tank.

Formal studies of these various related processes are termed ‘well to the wheel’.

These studies have been undertaken around the world by governments and other institutions to fully account for all energy consumed and greenhouse gasses emitted in the various stages before end use.

They help us move closer to answering our main question.

Well to Wheel

Such studies going back over 10 years have consistently noted that adding electrification to our transport can result in gains in efficiency compared with reliance on internal combustion alone.4

Several well-to-wheel studies commissioned by the US Department of Energy using the GREET model (Greenhouse gases Regulated Emissions and Energy Use in Transportation) showed the reductions in Greenhouse gases produced by increasing levels of electrification did vary depending on how fuel efficiency was calculated and how electricity was generated.5

This highlights that the energy source used to generate electricity is an important element to consider when comparisons are made.

Further more recent studies that include the complete life cycle of different types of vehicles, as well as their well to wheel data have revealed that even with fossil fuel-based electricity generation and power losses during transmission from electricity generation to filling the battery, electric cars were found to have lower levels of greenhouse gas production.

Dr Maarten Messagie from University of Brussels, in his 2017 paper Life Cycle Analysis of Climate Impact of Electric Vehicles, presents data showing that even in the most coal heavy power grid in Europe an electric car still emits 25% less GHG than a comparable diesel vehicle.6

In Australia Whitehead, Smit and Robinson reveal that, primarily through their efficiency, even on the coal rich Australian grid, EVs produce 40% less GHG when compared with equivalent ICE vehicles.7 (p.20)

In fact, their well to wheel calculations show that to drive 1km in an average petrol vehicle uses 1.36kWh/km while the average figure for electric cars is just 0.28kWh/km – an energy use figure close to five times less than for petrol cars.

For the most efficient electric vehicle coming onto the market, the 2020 Tesla SR+, the figure is eight times as efficient as the average Australian car. 8

Cradle to Grave

Similar efficiencies have been found in US studies.

The Union of Concerned Scientists publication Cleaner Cars from the Cradle to Grave examines in detail the effects of the differing local grids that make up the US electricity network have on the GHG performance of electric vehicles.

Their findings were that even on the very dirtiest coal fired grids, such as in states like West Virginia, electric cars produced a 21% improvement over new petrol car average economy.9

They also noted that few electric cars were sold in these areas and that based on 2014 sales data the average EV in America cut GHG emissions by 60% compared with the average petrol car and achieved GHG emissions far below that of even the most fuel-efficient hybrid vehicles.10 (p.11)

The higher percentages in this study compared to the Australian and European ones mentioned above would be mostly explained by the greater size and weight of the ‘average’ American petrol vehicle.

This study found that when it came to making electric vehicles GHG and other emissions were considerably higher than for comparably sized conventional vehicles.

Much of this is due to the mining of materials for, and manufacturing of, the battery. The examples used in the study, a Nissan Leaf and Tesla Model S represented a 15% and 68% increase over comparable vehicles.

However, in both cases the extra emissions were offset, even in the dirtiest grid option, by driving 13,000 miles and 39,000 miles respectively.11 (p.22)

Changing Nature of Power

Of course, the above statistics represent worst case scenarios for EVs – which have a special advantage over ICE vehicles. What is this advantage?

It is the changing nature of energy production.

Although ICE vehicles are much more efficient today than those made even 10 years ago; as soon as an ICE car is purchased, it continues to burn fossil fuel-based energy at a similar rate throughout its working life.

Electric cars; however, are getting cleaner every year. How?

The increasing amount of renewable power coming into the grid means that as time passes EVs improve their GHG profile.

In early 2019 the National Energy Emission Audit revealed that Australia’s proportion of energy generated by renewable sources is at 21%. Just 10 years before that figure was 6%.12

In the future, as the percentage of renewables increases further, EVs will continue to become cleaner still, with the eventual end goal being a decarbonized grid like Norway, with over 95% of power sourced from renewables. In Australia, many EV owners aren’t waiting on the grid though.

With one of the highest take ups of solar energy in the world many Australians could power their cars at least partly with energy drawn from their own roofs.

Although hardly a precise poll, a recent show of hands of electric vehicle owners at a Queensland meeting of the Tesla Owners Club of Australia showed that approximately 70% of attendees also owned solar panels.

The ‘Other’ Studies…

There are often articles cropping up in the press that state electric cars are not much better than fossil powered ones.

Most of these pieces are based on flawed or skewed research, inaccurate methods of measuring fuel economy (like Australia’s own NEDC standard) or use artificial assumptions about the lifespan of various technologies, states Auke Hoekstra, in the journal Joule.13  

Hoekstra, from the Department of Mechanical Engineering at Eindhoven University of Technology, methodically picks apart the assumptions and methodologies of numerous academic papers on electric cars which claim minimal benefit from EVs. Hoekstra exposes their weaknesses, which include:

  • overestimating battery manufacturing emissions
  • underestimating battery lifetime
  • assuming an unchanged electricity mix over the lifetime of the EV
  • using unrealistic tests for energy use
  • excluding fuel production emissions

So, when you next read an article that claims we are better off with fossil fuel vehicles, think critically about where the data is coming from, as much as which organisation is publishing it.


Electric motors have been proven to be considerably more efficient than the internal combustion engine as a means of powering cars.

Furthermore, although electric vehicles require more resources and more greenhouse gases are emitted during their production, they have been proven to be cleaner – largely due to their incredible efficiency. This has been found true even on a ‘dirty grid’.

When you take into account that across the world power grids are becoming cleaner – the gap between the EV and the ICE vehicle will only grow.

This means the answer to the question of which car is cleaner is clearly the electric car.

If only I had known this at the time, I would have won the argument with my friends and saved myself the expense of buying the next round.


1, 3, 7, Whitehead, Jake & Smit, Robin & Washington, Simon. (2018). Where are we heading with electric vehicles?  52. 18-27. JOURNAL OF AIR QUALITY & CLIMATE CHANGE:


John Cuprisin, Associate Professor Automotive Technology at Pennsylvania College of Technology (2000-present)

4, Kromer, M. A.; Heywood, J. B. (2007) Electric Powertrains: Opportunities and Challenges in the U.S. Light-Duty Vehicle Fleet, MIT Laboratory for Energy and the Environment, Cambridge, Massachusetts.

5, Well-to-Wheels Analysis of Energy Use and Greenhouse Gas Emissions of Plug-In Hybrid Electric Vehicles, by A.Elgowainy, J Han, L. Poch, M. Wang, A. Vyas, M Mahalik & A. Rousseau, Energy Systems Division, Argonne National Laboratory. June 2010.

6, Maarten Messagie – Vrije Universiteit Brussel – research group, Life Cycle Analysis of the Climate Impact of Electric Vehicles


9, 10, 11,


13, Auke Hoekstra, The Underestimated Potential of Battery Electric Vehicles to Reduce Emissions, Joule, Volume 3, Issue 6, 19 June 2019, Pages 1412-1414!

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