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Do electric cars cause more or less climate pollution than gasoline cars? Take a look.

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  • 6.5 tCO2 to build average gasoline-only vehicle
  • 13.7 tCO2 to build average electric-only vehicle (car = 8.5 tCO2 and battery = 5.2 tCO2)
  • Extra 7 tCO2 to make electric car. My chart's black and purple bars let you compare these amounts relative to the overall climate pollution for each vehicle.

The study I used to determine the climate pollution from building vehicles is "Comparative Environmental Life Cycle Assessment of Conventional and Electric Vehicles" from the Journal of Industrial Ecology. I picked this study for two main reasons.

1)    It is an in-depth and "transparent" life cycle inventory. That means all their data and assumptions are public and available for download on their website.

2)    It does not seem to have a bias towards electric vehicles. It has the highest CO2 values for production of electric vehicles and batteries of any study I looked at. In addition it was used to attack electric vehicles as good climate policy by a prominent climate delayer writing in the oil-friendly Wall Street Journal.

Q: How long do electric car batteries last?

A: Likely for at least half the lifespan of the car, and possibly the whole lifespan.

DISCUSSION: The average lifespan of a car today according to government data is around 200,000 miles (320,000 km).

As far as I could find out nobody knows exactly how long the plug-in traction batteries will last in real world conditions. These batteries haven't been on the roads long enough.

What is known is that stress tests and other research has been done to decide what warranty levels are financially viable for the auto companies. The standard warranty on plug-in traction batteries (Leaf, Volt, Plug-in Prius) is for 8 years or 160,000 km. Telsa offers 8 years or 200,000 km. This implies that traction batteries are expected to last well beyond half the lifespan of the average car.

Another data point is that the regular, all-gasoline Toyota Prius has the same 8 year or 160,000 km warranty on their traction batteries. After a decade they claim 99% of these cars have not needed to have a battery replaced. They also point to taxi cabs that have travelled over 500,000 km on a single battery. However these batteries are a different technology from plug-in batteries, so it is still an open question if plug-in batteries will fare as well relative to the company's offered warranty.

Bottom line, plug-in batteries may need to be replaced once during average lifespan of a vehicle.

Q: How much climate pollution would result from replacing an electric car battery?

A: Around 5 tCO2

DISCUSSION: The study I used (see above) estimates around 5.2 tCO2 is released in making a plug-in traction battery. My chart makes it easy to see the climate impact of adding a replacement battery. The each purple bar represents one battery, so adding as second purple bar will show the climate impact of adding a second battery. Here is part of my chart with a second battery added:

 

Note that in a clean electricity region, the addition of a second battery doesn't change the general conclusion that electric vehicles produce significantly less overall climate pollution than the best all-gasoline vehicle. In some dirty electricity regions, however, a second battery might tip the scales.

Q: Is it better for the climate to just keep driving my car as long as possible?

A: Probably not. Continuing to drive most cars will cause more climate pollution than if they were recycled and replaced by a less climate polluting alternative.

DISCUSSION: There are many reasons to keep using something as long as possible. But for most cars climate pollution isn't one of them.

In fact climate pollution would be reduced if most cars, even brand new ones, were recycled immediately and replaced by less polluting alternatives.

If this seem counter-intuitive, take a look at the average car on my chart. Building it creates 7 tCO2, while burning gasoline to "keep driving it" creates 102 tCO2. Driving the car requires burning nearly 30 tonnes of gasoline. The gasoline overwhelms the car itself both in terms of weight and climate impact. Driving the car, not building it, causes almost all the climate damage.

In comparison a regular Prius burns half as much gasoline. By slashing gasoline consumption, climate pollution is slashed by 57 tCO2. That more than makes up for the climate pollution to build the vehicles.

Here is the climate math:

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