Coal-fired Teslas

Electric cars are touted as the transport solution to reducing greenhouse gas emissions and saving the planet from excessive warming. If only it were so simple…

Drive a Tesla Model S for 100 miles, and it will use 34kWh of electricity. In petrol terms, that is about 100 MPG and sounds like a win for the driver. If electricity costs an average of $0.12/kWh, the yearly cost to drive a Tesla Model S 15,000 miles is $612.

Not bad and much cheaper than gas.

Driving those 15,000 miles of silent motoring pleasure needs roughly 5,000 kWh.

But what about the carbon emissions? 

A new petrol car would be expected to release around 4.4 tCO2e to cover the same yearly distance.

Surely an electric car would have fewer emissions.

The energy efficiency of electric engines is better for the atmosphere than internal combustion engines. And using electricity to drive the car means no exhausts and no nasty fumes. Aside from the embodied energy in the materials that make up the vehicle the carbon footprint should be minuscule.

Perhaps.

The thing is it depends where the electricity comes from. 

Over 56% of the electricity in U.S. comes from coal-fired power stations. More than 84% of the coal consumed each year in the U.S. is used to generate electricity; in Australia it is 75%.

Here are the global numbers from the International Energy Agency in TWh from 2002 to 2017 and projected to 2030.

Light blue is coal, dark blue natural gas and green renewables.

It will take a while before most energy generation is from renewables with a low emissions footprint. In the meantime, at least half the electricity will be from coal.

Back to the emissions from the Tesla.

It takes about one pound of coal (0.45 kg) to generate one kilowatt hour (kwh) of electricity. So each Tesla needs 2,250 kg of coal to produce the electricity for its yearly travel.

Turns out that coal has a carbon intensity of about 1,000g CO2/kWh, oil is 800g CO2/kWh, natural gas is around 500g CO2/kWh, while nuclear, hydro, wind and solar are all less than 50 g CO2/kWh.

The two metric tonnes of coal generating the 5,000 kWh of electricity to power the Tesla for 15,000 miles releases around 5 tCO2e — a little more than the petrol model.


What sustainably FED suggests…

Until there are none left to buy, maybe get a second-hand petrol car. By the time the stock of petrol vehicles is used up, renewables would give electric cars the emissions profile we think they currently have.

Encourage the divestment from fossil fuels, especially coal, but remember that people need electricity for health and well-being. Not everyone can afford to pay heavily for it, especially in developing economies where the alternatives to electricity are charcoal, wood, and cattle dung.

The 2,450 coal-fired power stations globally should become stranded assets but only when there is enough generation capacity in alternatives.


Hero image modified from photo by Martin Katler on Unsplash

Mark

Mark is an ecology nerd who was cursed with an entrepreneurial gene and a big picture view making him a rare beast, uncomfortable in the ivory towers and the disconnected silos of the public service. Despite this he has made it through a 40+ year career as a scientist and for some unknown reason still likes to read scientific papers.

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