Teslas in Victoria aren't greener than diesels

The Tesla in front of me was shiny, sleek and silent, but my Fast-&-Furious-inspired daydreams were interrupted with a question: does a Tesla charged by Australian electricity emit less CO₂ per kilometre than an efficient diesel car?

The answer turns out to be: no in Victoria, yes in Tasmania or South Australia, and in the other states it’s pretty much even.

Tesla Model S CO2 emissions-per-km, a comparison of charging from electricity in different states across Australia.

The Australian grid

The emissions of a Tesla turn out to be a good indicator of the cleanliness of the Australian grid. Tasmania, with 70% hydro, and SA with its 30% wind power make Victoria stick out like a sore thumb with more than 50% brown coal electricity and emissions of 1.18 kg of CO₂ per kilowatt hour (according to the federal Department of Environent and the Australian Energy Regulator).

About 87% of Australia’s electricity is currently generated by burning fossil fuels, resulting in average emissions of 0.85 kg_CO2 per kWh. This will have to come down for electric cars to have an impact on our emissions. It’s something that’s starting to happen with the massive expansion in rooftop solar. Indeed, if you charged your Tesla with your own solar panels you’d be cruising pretty cleanly.

Of course, the fairer comparison for a Tesla isn’t a super-efficient small car, but something more like a luxury sedan with grunt. Comparing an Audi A7, Holden Commodore, a Toyota Prius and a 1984 Volvo station wagon (for comparison with an older car) yields an interesting graph:

CO2 emissions using fuel economy data from the US Environmental Protection Agency, Fuelly and the Dept. of Environment.

Green fuels

Teslas are CO₂-greener than most cars in Australia, though not by as much as you’d expect. Does it change if the cars run on biodiesel?

Calculate your own CO2 emissions. Start at your fuel efficiency (in L/100km) on the left, go right until you hit your fuel-type line, draw a line straight down, and read off your CO2 emissions per km.

A little, as the emitted CO₂ was originally sequestered from the atmosphere by the plants in the first place. We can calculate fuel emissions simply by multiplying the fuel efficiency of your car (in litres per km) by the CO₂ emissions from burning each litre of fuel (2.35 kg _CO2 per km for petrol and 2.68 kg _CO2 per km for diesel).

The emissions for biodiodesel decrease by the proportion of plant-derived diesel in the fuel blend (typically 80% diesel, 20% biodiesel). It’s similar for ethanol blends (typically 90% petrol, 10% ethanol), although filling an old Volvo or a Holden V6 with ethanol wouldn’t make too much of a difference. The hybrid Toyota Prius has the least emissions by far – owing to its exceptional fuel efficiency, something that hasn’t gone unnoticed by the taxi industry.

Delving a little deeper into the question, the Australian government also provides “Scope 3” emission assessments of electricity that take into account indirect emissions from resource extraction and transport. Including these results in about 15% more emissions from electricity than Scope 2 data – what the above assessment uses.

At this level of detail, though, we should probably start thinking about exactly how we drive (the above figures use combined city and highway mileages from the US Environmental Protection Agency and Fuelly), and also compare the lifecycle cradle-to-grave costs of each of the cars.

The author’s not-so-green Volvo.

More than 10,000 Teslas were sold in the first quarter of 2015. The latest shipment to Australia has just arrived and the company is building a supercharger network connecting Melbourne, Canberra, Brisbane and Sydney to be completed in 2016. It’s a glimpse of an exciting future - the coolest thing about Teslas is that they are cool.

But Australian grid electricity will have to become greener before electric cars take a chunk out of our CO₂ emissions, especially in Victoria. Here’s to hoping that Fast & Furious 8 will be filmed with electric cars running on green Australian electricity.

Niraj Lal receives funding from the Australian Renewable Energy Agency and is a member of the Australian Greens. The article's comparisons formed one of the exam questions for the 4th year course he lectures on Energy. Niraj declares no competing interests except an affection for his unfortunately polluting ’84 Volvo Station Wagon.