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Creativity with data helps EV sceptics obscure the facts

Posted by Leighanne: Nov 15, 2017 5 min read

A recent study by the Massachusetts Institute of Technology (MIT) caused a flurry of headlines over whether EVs really are greener than petrol or diesel.

James McKemey, our Head of the Insights Team, gives his take on the study and one newspaper’s coverage of the results:

It’s fair to say the Daily Mail hasn’t always been a vocal supporter of electric vehicle (EV) technology.

Its recent article, however - Electric cars are NOT as green as you think (and some are worse polluters than petrol!) - takes it up a gear, veering from sceptical to plain misleading.

Based on an “interpretation” of the findings of a study by the Massachusetts Institute of Technology (MIT), the article has caused a stir among the EV community, which tends to be pretty passionate about all things CO2. As a professional in the EV field and a huge believer in sustainable travel, it would feel remiss of me to let the assertions from this hugely influential publication go unchecked.

Let’s take a look at how the article’s claims stack up against the actual findings of the MIT study. Brace yourselves, this is about to get technical...

Outliers are the exception, not the norm

The first point of contention is the phrase: “Tesla S P100D saloon produces more CO2 than petrol-driven Mitsubishi Mirage”. The MIT team found a freakish example where, over the whole life of the vehicle (including manufacture), the Tesla Model S would have higher emissions than a super-efficient (for petrol, anyway) super mini, the Mitsubishi Mirage. This example was the overnight grid in a part of the US midwest that has an eye-watering average Carbon intensity of 857 gCO2eq/kWh.

By comparison the UK hasn’t reached 600 gCO2eq/kWh since the very depths of winter 2013 at peak. The average grid intensity in 2016 was 320 gCO2eq/kWh. As the UK electricity supply draws more and more from renewable sources, this will be proportionally lower in 2017, and again in 2018, and again in 2019, and…you get the idea. Furthermore, this 320 gCO2eq/kWh is an overall average, but most charging actually happens overnight, when it has a far lower carbon intensity (it fell as low as 90 gCO2eq/kWh at one point during summer 2017). Based on the data available, I would say a fair average “overnight” 2017 UK grid mix would be circa 225 gCO2eq/kWh.

So, let’s do the maths. Using the online calculator and “average” conditions (i.e. 10 celsius outside temperature, heater on, 55 mph average speed, big flashy wheels) Model S P100D will average roughly 4.54 km/kWh. This means the equivalent, overnight g/km for the P100D in the UK would be 49.6g/km. Or if you average the whole of 2016, it would be 70.4 g/km. The Mirage remains at 192 g/km, and that’s if we’re generous and don’t account for the huge Carbon consumption in getting that fuel from an oil field to a fuel station (I’ve no idea why we offer such staggering generosity towards OPEC, but such is convention). The next point is it’s never going to get better than 192 g/km. This is in contrast to EV technology, which is already superior in this area and continues to improve year on year.

So why didn’t the MIT report make a similar point? Oh wait…it did. The researchers gave several scenarios and an overall graph. EVs win. It’s as clear as day, but they also highlight the importance of grid mix and that smaller EVs are a tad more efficient than large ones. Smart bunch at MIT, you see.

This brings me back to my original point of contention. Saying the “Tesla S P100D saloon produces more CO2 than the petrol-driven Mitsubishi Mirage” is a bit like saying “a British salmon is a slower animal than a mid-western American snail”, a claim that could potentially be true under a very specific set of conditions: i.e the snail is slithering flat out across a mid-Western plain, next to our British salmon, who has sadly expired. If this sounds ridiculous, well, the claim made in the Daily Mail article is equally outlandish.

Behold the exciting potential behind the snark

The writer does make one excellent point in the article, although I’m not sure this was intentional. He writes: “Unless you have your own private power station that runs on renewable energy, the chances are that you will be using the National Grid to charge your car overnight”. Well yes, EV drivers do broadly rely on that ever-greening grid. And the idea of your own private renewable power plant at home is just as absurd as your own oil well and refinery, right?

Actually, no. You can have just such a renewable power station at home. Solar generation and storage are two technologies whose costs are both in precipitous decline. It is already possible to collect electricity through solar panels, store it in a battery and then use it to charge your car overnight. Alas it is costly, and the panels not to everyone’s aesthetic tastes. Both of these things are being fixed. And fast. This combined technology will totally revolutionise our energy usage over the coming years, hugely decreasing/eliminating our dependence on fossil fuels from the grid.

Summing up

The future is bright for EVs, which are exactly as green as we thought and getting greener faster than many can keep up with. Now that’s settled, can we start comparing Tesla Model S vs Mitsubishi Mirage performance? Or, to make it a fairer contest, how about a P100D vs a Lamborghini Aventador?