By Clayton Handleman
I have not been too surprised to see Tesla getting skewered in the press. It is the way of the press to try to create conflict and controversy and to go after the top dog. However I was surprised to see a recent Climate Central report suggesting that the Tesla has a much larger carbon footprint than the Leaf due to its larger battery. In another post I look at the case for EVs in a great deal more detail but this post keeps the focus on Tesla.
I would go as far as to claim that the report is flawed in that they show the Tesla as being inferior to the Leaf in terms of the energy balance without so much as a footnote pointing out that there are important differences that should be taken into account. They use the same lifecycle assumptions for the Tesla battery as for the Leaf. However, the larger battery and range extend the battery lifecycle for the Tesla considerably and this is reflected in the battery warranties for the two vehicles. Leaf has 60,000 standard while Tesla has a 125,000 mile x 8 year standard with unlimited mileage available for a relatively small upcharge.
The larger battery extends life-cycle in two ways. First Tesla’s longer range implies that the battery will require half of the charge discharge cycles to go the same distance. This allows the battery to have a substantially longer lifetime. But it gets even better for the Tesla.
Battery lifetime is extended if you don’t top off the charge. It turns out that you can substantially extend the battery lifetime if you only charge to 85% and discharge to 15%. This is much easier with the Tesla due to the range. Also the Tesla enables the user to fully control the charging of the battery. You can actually set it to charge only to the 85% point. You can set it for full charge only on the days where you will need the extra range. All of this means that the Tesla battery will last much longer than a Leaf battery.
One could also point out the nearly all aluminum construction of the Tesla as being energy intensive. However with that much aluminum in one place the scrap value will be very high and lead to a high recycle percentage. This further reduces the carbon footprint.
The Climate Central report uses two scenarios, 50,000 and 100,000 miles to compare all of the choices P 17. The study would have been much more useful if it had used the typical warranty periods as the benchmarks to assess the vehicles. I.e. 60,000 miles for Leaf and 125,000 miles and 250,000 miles for the Tesla. Below look at the difference when taking into account longer total miles driven:
Ranked Lifecycle Emissions based upon driving the distance shown and using the average mix of electricity.
Car 50kmile 100kmile The Percentage improvement taking longer range into account
Prius Hyb .84 .68 19%
Leaf 1.0 .73 27%
Tesla 2.07 1.34 35%
To extrapolate this to the likely lifecycle of the Tesla, the Leaf will take a big hit. In fact, it is likely (based upon their battery warranty) that the Leaf battery will need to be replaced before the 100 kmile point making the 100kmile number for the Leaf substantially underestimated. With the Tesla if we assume another 35% reduction to get to 200 kmiles then the Tesla will close in on the Prius because much of its carbon footprint will continue to be fuel while Tesla is still amortizing the battery (improving at a higher rate on a per mile driven basis). And remember the Prius battery is only warrantied for 100k mile so it may need replacement as well. What is clear is that in a life-cycle analysis, the Tesla is comparable to the Leaf and probably better. It also closes in on the Prius. Whether it would catch it requires a more detailed study.
This report has been out for some time. It is unfortunate that it has received as much press as it has. While there are few facts that could be called wrong, the way that the facts are put together could easily lead a reader to the conclusion that EVs are not yet ready to be mainstreamed. This is unfortunate since compared to the average internal combustion (ICE) EVs are a better choice everywhere INCLUDING where coal dominates in electricity generation.