A new study released this month by Ecometrica, comprehensively extrapolates the carbon dioxide (CO2) emissions of cars powered by either gasoline, diesel, or electricity. As such, Ecometrica's findings allow us to answer the question - does driving an electric vehicle reduce CO2 emissions?
Before I reveal the answer to that, here's a bit of background. The company authoring the report is a Scottish based specialist in greenhouse gas (GHG) accounting, ecosystem services, and climate change policy. They are the carbon-calculator partner of the Carbon Disclosure Project (CDP), which speaks to their credibility. The data they collected was crunched to measure equivalency in terms of grams of CO2 emitted per kilometer traveled (gCO2/km). They looked at range and battery capacity of EVs on the market, and used data on grid carbon intensities, to calculate CO2 emissions per kilowatt hour (kWh), taking into account power station energy losses, and transmission losses. And to make for a suitably rigorous comparison, they chose highly fuel efficient gasoline and diesel powered vehicles in order to, as they claim, paint the worst case scenario for the electric car.
And so, to the results!
1) An efficient new diesel car emits 99 gCO2/km. An efficient new gasoline powered car emits 159 gCO2/km. The UK government figure for the average car on UK roads is 208 gCO2/km. And to put these numbers into perspective, the perennial benchmark of efficiency - the Toyota Prius - achieves 89 gCO2/km.
2) EV emissions, by comparison, are much more variable, because their carbon emissions are directly related to the mix of power generation by each country. In order of lowest to highest, here are the emissions for EVs driven in the countries included in the study:
Only residents of China and Greece will increase their carbon footprints by switching to EVs, that is if they're already driving efficient diesels. This is because of the prevalence of coal fired power generation in these countries, which put EVs at a disadvantage. Hat's off to France for coming in at a rock-bottom 12 gCO2/km, the EV wins by a huge margin - but um...nuclear power, anyone? The UK and USA use a mix of coal, oil, gas, nuclear and renewable generation for their grids, so on today's blend, EVs win here too. But Canada has to be the winner: with its high proportion of hydro-electric power generation, EVs take the day with lots of renewable energy, without the risk of reactor melt-downs.
So really, despite the continued existence of range anxiety, the case for the EV is very strong. They are almost always better from a carbon emissions perspective, but while noting that, we cannot - based on this data - categorically assume that no matter however electricity is generated, its all good. It's vitally important that renewable energy be an increasing part of the mix of power generation in future, if we are to be assured that electric vehicles will bring to bear promised carbon emissions reductions. Either that, or we'll need to build more nuclear plants, but I hardly need to highlight the downside of that approach. I'm sure many other studies have been done to answer the question as to EV CO2 emissions, so it would be great to hear about those that support, or run contrary to, this most recent study.
Phil Covington holds an MBA in Sustainable Management from Presidio Graduate School. In the past, he spent 16 years in the freight transportation and logistics industry. Today, Phil's writing focuses on transportation, forestry, technology and matters of sustainability in business.