Electric vehicles like: trams; trains; and electric: cars; vans; and busses; all assist in achieving better air quality in our cities. Yet, to the extent that the energy they consume is derived from our oldest energy source, fire: the potential toxic emissions and greenhouse gasses simply enter the atmosphere somewhere else.

Back in 2005 I calculated that in Australia, due to our burning coal, oil and sometimes rural waste and garbage, to generate electricity, grid-charged all-electric electric cars had a higher carbon footprint than conventional cars.

In 2019, with a lot of water under the bridge; more renewables in the mix; and much improved batteries; I thought it was worth a revisit. I ran the numbers, using more real-world data, including those published by car companies themselves. Yet I got the same result: In Australia, grid-charged all-electric cars produce more greenhouse gasses than many conventional cars for the same distance travelled.

Now, in the wake of COP26, (November 2021), with even more water under the bridge, the promotion of electric cars is back on the political agenda.  Has anything changed?

The last time I visited this topic I pointed to the huge improvement in, both the energy density and weight of batteries and to the substantial increases in both electricity and petrol prices, during the first two decades of the 21st century.

Together, these have altered the cost-benefit equations for electric cars, in many places, making Elon Musk, founder of Tesla, one of the two wealthiest people on the planet. 

Yet, in Australia, a smaller carbon footprint than cars using petroleum directly, remains elusive.

Conventional petrol driven cars, obviously, get their energy from petrol and/or liquid petroleum gas. Yet like all internal-combustion powered vehicles, they lose a great deal of this energy as heat. Typically, over 70% of the energy contained in the fuel is lost. In other words, the waste heat generated is responsible for most of the vehicle's CO₂ emissions.

As the actual emissions vary, from vehicle to vehicle and depend on fuel consumption under different driving conditions, these data can only be determined from actual vehicle trials. In Australia these are periodically compiled by The Green Vehicle Guide (GVG) - an Australian Government initiative.

According to the latest report, the average combined CO₂ emissions for new light, petrol driven, vehicles sold in Australia was 18.2 kg/100km, in 2017, and has fallen in many vehicles since.

Hybrid vehicles use an electric motor and a large battery. An internal combustion engine keeps the battery charged and provides supplemental mechanical power. The internal-combustion engine suffers similar losses to a conventional vehicle but, like all-electric vehicles, hybrids are able to recover some of the kinetic energy, previously invested during acceleration and hill climbing, by regenerative braking: recharging a battery when descending, slowing or stopping. The electric motor also enables more efficient use of the internal combustion engine, by minimising its use during acceleration.  

All-electric cars, on the other hand, get most or all of their energy from the electricity grid (sometimes complemented by domestic solar).

But electricity is just an energy transport medium; not a source of energy in itself. (See How does electricity work? on this website.)  Thus, all-electric vehicles are using energy from somewhere else like: the wind; the sun (atomic fusion); atomic fission; falling water; or, in Australia, mostly from burning something.

So, to find an all-electric car's carbon footprint, we need to consider where the energy, transported by electricity, comes from; and how much CO₂ (equivalent) that source generates. We also need to factor-in how much of that energy is actually delivered to the vehicle, because that varies.

In transporting energy to a charging station over the electricity grid some of it gets lost. Depending upon where a car is charged, as much as 10% may be lost as the energy is transmitted over the grid.

In addition, there are losses converting the current to a car-friendly voltage and waveform (flat), once received from the grid. 

In most of Australia, the energy available from the electricity grid is predominantly derived by burning coal and gas.

According to the Australian Department of Industry, Science and Energy and Resources the CO₂ (equivalent) emitted by electricity generators in different States in Australia varies as follows:

Depending on the energy source used, the emission factor (the CO₂ emitted for each kWh of electrical energy consumed), varies quite dramatically between the States. 

The average CO₂ released by Australian electricity generators in 2019-20 was 0.73 kg/kWh.

To make a comparison between vehicle types, I've chosen three indicative brands of car, together with the light passenger vehicle mean (see above) for comparison.

First, let's look at their energy consumption:

• the Tesla Model S 70, all-electric, that consumes 18.5 kWh/100 km (as published by Tesla);
  the Tesla (performance) Model X, all-electric, that consumes  22.6 kWh/100 km (as published by Tesla);
• the Toyota Prius, hybrid, that consumes 33 kWh/100km (3.4 litres of petrol/100km*); and
• the fuel-efficient conventional Audi A1 that consumes 42.7 kWh/100km (4.4 L/100km*). 

*Petrol produces 2.31 kg of CO₂ and yields 9.7 kWh per litre.

So, in 100km:

• the hybrid Toyota Prius produces almost 8 kg of CO₂ (3.4 x 2.31 = 7.85):
• the conventional petrol-driven Audi A1 produces about 10 kg of CO₂ (4.4 x 2.31 = 10.16);

Using the Australian average emission factor for electricity consumption and making no adjustment for remote or unusual grid, inverter or transformer losses at remote sites the:

• the all-electric Tesla models produces between 14 kg and 17 kg of CO₂: (18.5 x 0.73 = 13.5; 22.6 x 0.73 = 16.5); while 
• the average light vehicle sold in Australia produces 18.2 kg of CO₂ (according to the AVG link above)

But if charged from the grid in Victoria, the all-electric cars produce from 18 to 22 kg of CO₂. This will improve when Victoria has phased-out brown coal and replaced the base-load generation with gas. Yet, the 'carbon footprint' of grid-charged all-electric cars is not a lot smaller in Queensland or in NSW.

This puts a Tesla right in the middle of all (predominantly petrol fuelled) light vehicles sold in Australia, in terms of CO₂ produced per 100km.

Since I first checked in 2005, as more renewables have come on-stream, the all-electric vehicles' once much larger 'carbon footprint' has shrunk substantially, But the present ranking in no way justifies the present 'greenwashing' of all-electric cars. Particularly when hybrids do a lot better.

So, if you are concerned about your carbon footprint, unless you live in Tasmania or South Australia, and don't often travel interstate, don't buy an all-electric car in Australia. Buy a hybrid.

Hybrids presently have the additional advantage over all-electric cars in that they are not as distance or location constrained (you can get petrol almost anywhere); do not require any charging time during a long trip; and replacement batteries (when the time comes) are smaller and thus considerably cheaper.

Alternatively, a small advanced conventional petrol driven car like the Audi remains a more environmentally friendly solution than an all-electric car. 

So, if someone gave me a Tesla Model X or the new plug-in Jaguar I-Pace, I would probably keep it for showing-off around town, with a relatively clear environmental, if not egalitarian, conscience. Both have brilliant performance statistics and are very cool.

Yet my present, not-very-cool Holden is almost as 'green'. And even my Holden's performance is difficult to realise when our maximum speed limit is 110 km/hr. Given the need to interrupt a journey to charge, I'd also have to keep my Holden for trips into the country, where charging might be a problem, or to drive to Melbourne or Brisbane. It's also roomier and less precious to take to the supermarket and hardware store, where it occasionally gets dented.

Of course, if we had a lot more renewable energy, electric cars would make more sense.

If NSW or Victoria could generate most of our electricity from hydroelectric resources, like Tasmania (and they'd have even more to export if not for Bob Brown); and if everyone could drive across our island in a day; then the environmentally concerned among us should go out and buy an electric car tomorrow. 

For the rest of the country, the main incentive to buy for all-electric cars is not saving the environment but the increasing cost of petroleum fuels, that attract a road tax, compared to relatively low cost of tax-free electricity.

As the purchase price of all-electric cars falls, this saving is becoming more attractive.  

At the moment, the main beneficiaries of this tax-avoidance are cruising around in up-market luxury sports-sedans.

These plug-in vehicles travel on roads that the, mostly wealthy owners, are not paying for, while the average family currently pays over a thousand dollars a year in fuel excise.

So, it's not at all clear to me why taxpayers are being encouraged to pay for more charging stations to assist these car owners to dodge road tax.

Perhaps this tax avoidance can be tolerated for a short time, while numbers are small, but it will need to be corrected as the numbers of electric vehicles grow. Perhaps all-electric vehicles will soon need to be levied an extra thousand-dollar-plus registration premium to compensate?

Might this cause those who make such a purchase, without being informed of this likelihood, to get upset? Like those who unadvisedly decided to install solar panels, in excess of their own needs?

In Australia, if we want to match European attainment and make fully electric cars environmentally worthwhile, we need to find a new low-carbon base-load electricity technology to replace coal. Yet there remain some significant constraints to achieving this.

We have a highly centralised urban society with very long loss-making grid lines between centres. Unlike Europe it's a dry continent with insufficient hydro resources to make a big difference and while there is ample wind and solar in remote areas there are few well-placed wind prospects within a practical distance of Sydney or Brisbane.

South Australia has many excellent wind prospects but, like Denmark, South Australia is now effectively saturated with wind, generating much more electricity than the State can consume at times; while falling short at others. 

As I have explained elsewhere, the cost of wind-power is entirely due to the capital and maintenance cost of the equipment and associated grid. So, in practical terms adding more wind turbines, or batteries, to make up for times of shortfall, adds significantly to electricity costs. 

As a result, South Australia, that has prematurely retired its thermal base-load generation, and is too remote to share excess generation with NSW or Queensland, has close to the highest electricity prices in the world. 

Fortunately, compared to the Australian electricity market overall, South Australia, is a very small component (5.9% see the table above).

While subsidised PV Solar is an option for domestic electricity, it's even more variable than wind and requires a large battery if the household is to be removed, even partially, from dependence on the grid.  At least the wind still blows just as much in winter; at night; or when it's cloudy.  Electric car users can install solar panels and charging equipment. But if they want to drive any distance from home during the day, it's a bit problematic and surprisingly expensive.

The present solar subsidy is funded by a small increase in electricity price, levied on everyone else.  As the table above shows domestic PV solar is presently a small contributor.  But if it were to become more significant the present subsidies would become increasingly unsustainable, perhaps limiting it's potential.  The subsidies are already criticised for discriminating against those who rent; or don't own a suitable dwelling; or who lack the capital to invest.

So - it's back on my hobbyhorse - we need to replace those filthy and unhealthy coal burning behemoths and their increasingly catastrophic ash-dams with nice clean nuclear stations. If we, do it in-situ, the existing grid and cooling infrastructure could be upgraded and the workforce and local residents would enjoy the improved environment.   

Just ask the French who get 72.3% of their electricity from nuclear reactors and export inexpensive electricity to most of their neighbours.