The Environmentalist's Dilemma: Electric Cars

Electric cars have the potential to dramatically reduce CO2 production in the United States; CO2 emissions from burning gasoline and diesel cause 1.5 billion metric tons of CO2 per year, which is 30% of total US energy-related emissions.

A number of friends of ours have electric cars, and hoo boy are they fun. (Got to drive a Tesla recently and holy smokes does it have some get-up-and-go.) A reader asked me recently how much an electric car--over lifetime--reduces CO2 output versus a conventional car. They wondered whether charging a car with a predominantly hydrocarbon-based energy grid actually helped the environment. It could be a major environmentalist's dilemma.

We decided to do the research. These are some very vague figures based on lots of averages. The idea is to get a close estimate of CO2 impact of electric cars vs. conventional. 

To get started, we need some key facts, and then we'll do some math in the analysis. We'll also stick to Massachusetts for this analysis--it's Erik's home state and electricity production varies from country to country.

Some Key Facts

Math Time

The Gas-Running Civic

For every 100 miles, a Honda Civic produces about (3.1 * 20 * 1.25) = 77.5 pounds of CO2

Over its lifetime (12,000 miles * 6 years), it will produce 55,800 pounds of CO2

Add its 17 tonnes of manufacturing CO2 (or 34,000 lbs), you get a total of 90,000 pounds

The Electric Leaf

Taking Massachusetts' mix into account, the total CO2 per kWh produced at night is about 0.9 lbs.

Therefore, for every 100 miles, a Nissan Leaf produces about (29 * 0.9) = 26 pounds of CO2

Over its lifetime (12,000 miles * 6 years), it will produce 18,700 pounds of CO2

Add its 19 tonnes of manufacturing CO2 (or 38,000 lbs), you get a total of 56,720 pounds

The Verdict

Over a very average car lifetime, your total CO2 footprint for an electric car will be something like 37% lower than a gas-powered sedan. If you live in Massachusetts. If you live in West Virginia, which is 96% coal, you'll be producing more than 2x the carbon while driving your electric car than if you live in Massachusetts. Then, you're only burning about 20% less CO2 over the lifetime of the car. (But, despite being all coal, still less!)

What's particularly interesting is that if you amortize the CO2 costs of manufacturing each car over those 6 years, you're banking 5600 (gas) and 6300 (electric) pounds of CO2 per year. 

If you're planning to switch from a gas powered car to an electric car, the added bump of CO2 means it'll take quite some time to "earn back" your CO2 savings. Let's do even more math real quick:

Bonus Math

CO2 manufacturing cost of a new electric car: 38,000 pounds

CO2 savings per year on average use vs. using your old electric car (in Massachusetts): 6,200 pounds

Number of years required to "earn back" the CO2 from manufacturing the new car (38,000 / 6,200) = 6.1 years, or the average lifespan of a car. In West Virginia, that earn-back time is about 11 years.

For the most immediate carbon impact, you might want to hold on to your old car a few years longer. Or, alternatively, commit to using your electric car for more than 6 years.

Other Factors

There is probably a long-term benefit to being part of the vanguard that pushes electric cars along the production curve. As they reach scale, they are likely become more efficient per mile, might become less CO2 intensive per unit, and (most importantly) will increase the load on the US electrical grid.

Coal plants are now no longer competitive to build, and renewables are becoming increasingly competitive. If many people were to buy electric cars, they would drive the building of new power plants (which have an initial CO2 footprint of their own, but that's for another time), which are more likely to be natural gas and renewable, which drops the CO2 output per kWh. 

So it's likely that the impact of your electric car purchase could be long-term positive, even if you don't run it into the ground. 

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Erik Fogg

We do politics, but we don't do the thinking for you.