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The Toyota Prius is available as a plug-in model, but I have a Prius that is only gas-powered, that is gas is the only fuel. I am wondering if the mpgE of the Tesla, 141, is so much better than the mpg of my Prius (average of 45 mpg), that the Tesla is more sustainable-- or is the embodied energy cost of the Tesla so much more that it is less sustainable? I know that the sustainability of electric power production varies across the U.S. Let's use the average nationally, 20% of all power comes from renewable sources today. Thanks!

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Operation

You can use AFLEET, the Alternative Fuel Life-Cycle Environmental and Economic Transportation tool, from Argonne National Laboratory, to quickly do this analysis.

Using the US average electricity mix, annual mileage of 12,400 (20,000 km) and plugging in 141 mpgE for the BEV (Tesla) and 45 mpg for the HEV (Prius), here's the GHG emissions results:

Annual GHG Emissions

That's 2,994 kg CO2eq for the Prius, and 1,452 (about half) for the Tesla.

Battery manufacturing impacts

The main difference in emissions from production of different vehicle types is the battery. From the open-access paper "Contribution of Li-Ion Batteries to the Environmental Impact of Electric Vehicles":

Environmental burden of ICEV vs BEV across four measures

The solid black bar represents the battery -- this is the point at which impact of a battery electric vehicle (BEV) and an internal combustion engine vehicle (ICEV) diverge. A hybrid, of course, would fall somewhere in between the two. So the question now becomes, what's the difference in impact between a Prius hybrid battery and a Tesla battery?

Estimates of emissions impacts from Li-ion battery production vary wildly, from 0.061 to 0.250 kg CO2eq per watt-hour. The range of production impacts for the two is then:

Tesla: 3,050 to 18,750 kg CO2eq
Prius:    45 to    186 kg CO2eq

Essentially, the Tesla battery is ~100 times bigger than the Prius, so the impact is ~100 times greater.

Comparison

From the factory, the Tesla has caused much more greenhouse gas (GHG) emissions. But it uses less per mile/km -- so at what point does it beat the Prius?

Here's a chart showing annual emissions per vehicle. The low and high estimates for the Prius are close, so I've just used the average.

Annual GHG emissions, Tesla Model 3 vs Prius

At some point between 37,000 and 241,000 km (23,000 and 150,000 mi), the Tesla will beat the Prius from an emissions stand-point.

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    I appreciate the detailed response. It appears clear that the Tesla with the smaller battery significantly reduces the overall impact, bringing the date when it is an improvement over the Prius much sooner. Can you clarify how you can say the Tesla battery is "10 times bigger than the Prius" when the Prius is listed as .75 kWh and the smallest Tesla battery 50 kWh? That looks like a difference greater than 66 times. – Jerry McIntire Mar 12 '20 at 17:02
  • @JerryMcIntire thanks, glad to help. Re: 10 times -- that was a typo. Fixed! – LShaver Mar 12 '20 at 17:14

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