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Could someone giver a clear and authoritative answer on HOW miles per gallon equivalent (or L/100 Km) are calculated for Battery electric Vehicles like Tesla Model 3 AWD long range? On the Electric Vehicle Alberta website it states that a Tesla Model 3 AWD Long range has a 1.8 L/100 km equivalent of mileage..But it shows the same value for all provinces...In reality this calculation will be affected by the particular mix to produce electricity in that province. The Union of Concerned scientist has a more granular values for mileage for US states. Each US state/Region has a different estimate for MPGe. https://www.ucsusa.org/sites/default/files/styles/original/public/2022-09/driving-cleaner-figure-2a.png?itok=jhyVduQa

How do you factor in the Carbon intensity of an electric grid? Burning one gallon of gasoline releases 115,000 BTUs of heat the average amount of electric energy needed to generate 115,000 BTU is 33.7 kilowatt hour so if a vehicle travels 100 mi for 33.7 kilowatt hours it said to have an effective mileage of 100 miles per gallon. I think the figure 33.7 kilowatt hour is an average. in actuality you have to scale it by Factor related to how clean the grid is. In effect in a cleaner grid you have to burn less gasoline to produce one kilowatt hour of electricity, and this affects the miles per gallon calculation..you essentially scale it by the carbon intensity of the grid? Even in a hypothetical 100 percent Clean grid, there is still the Carbon emission in the manufacturing of the Solar panel/windmill...In effect in a cleaner grid less Gasoline has to be burned for 1kWh of electricity in Car. Is this reasoning correct? You have to use a penalty/scaling factor to MPGe the calculations to account for how the Grid is powered in a region

How about the Lifecycle CO2 emissions of the electric vehicle and battery from manufacture to disposal? Is that also factored into Miles per Gallon Calculations per US state or Canadian province..or is that lifecycle only used for CO2 emissions over lifecycle, and only electricity generation is used for Miles per gallon equivalent calculations per province?

Could you please illustrate with a a simplified detailed hypothetical calculation for miles per gallon (or Liters/100 km) equivalent Two or Three Canadian provinces..Like Manitoba, Alberta, and BC, or Uses to show how differences in how electricity is produced in the region (mix of Natural gas, Coal, Hydro, nuclear, solar...) can be accounted for different estimate of MPGe? Use the Tesla Model 3 AWD long range as reference.

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  • The question has been cross posted in SE Engineering.
    – Fred
    Sep 3, 2023 at 8:01

2 Answers 2

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None of any "equivalent" figures make any sense.

Electricity and amount of liquid fuel have no relation to each other. Any relation "estimated" would be totally and completely arbitrary.

For example, if you have a large open cycle internal combustion engine power plant, it might let's say turn 45% of the energy content of a liquid fuel to electricity. So 1 liter of gasoline (~32 MJ, 8.9 kWh) would be about 4 kWh at 45% efficiency.

But wait! Combined cycle power plants exist and achieve 55% efficiency. So maybe it should be 4.9 kWh? But there's no way to decide whether 1 liter corresponds to 4 kWh or 4.9 kWh.

Also, electricity distribution efficiency varies, some areas might have better efficiency than others. How are you planning to take this into account?

You could consider CO2 emissions too. But emissions vary not only based on the location (for example, the Finnish electricity grid is very clean), but also based on time (is it windy, are some nuclear plants under scheduled maintenance?). Also do consider that electricity grids become all the time less reliant on fossil fuels, so over the 20-year life cycle of an electric vehicle, in the middle of it (after 10 years from now), electricity will create less emissions than it creates today.

I personally think that what you should consider is not emissions but total cost of ownership. Where I live today, if considering purchase of a new car, electricity wins so clearly there's no competition. But when considering whether I retain my old car or purchase a new one, the old car clearly wins. Unfortunately, eventually it will become so worn that I have to buy a new car, and this will be the time I will switch to electric vehicles.

It's true that battery manufacturing creates emissions, but it's a non-mobile emission source so easy to decarbonize. Most likely a large share of the energy comes from electricity when you manufacture batteries. About the only problem is that many batteries are from China and there electricity production isn't so clean yet.

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I think I found the answer to my question. I think what MPG estimates mean in this context is how many miles per gallon a hypothetical gas vehicle has to get in order to have the same life cycle emissions as the emissions of an average Electric vehicle in that region.For example driving the average electric vehicle in California produces as much life cycle emission as would driving a hypothetical gasoline vehicle which gets 109 per gallon over the gas vehicle's lifecycle(obviously a gasoline vehicle that gets 109 MPG doesn't exist,it's an abstraction). They consider life cycle emission for both the gasoline and the electric vehicle and scale accordingly.

You can see why this would be different in different electricity regions in the United States because carbon emissions are different based the energy mix of the electricity grid.. for example in Florida driving an EV will produce a life cycle emission equivalent to driving a hypothetical gas car that gets 73 miles per gallon, and in upstate NY driving an EV this MPG estimate is 249 miles per gallon! Because the Electric grid in upstate New york is so clean our hypothetical gas vehicle has to go 249 miles per gallon to produce as little of a life time emission as the average EV emits there!

The Miles per Gallon estimate by the Union of Concerned Scientists study. is different from the traditional Energy equivalent view of MPGe..which is computed like this (33.7 kWH of electricity, and combusting 1 Gallon of Gasoline both produce 115000 BTU of heat). It is a matter of semantics, the emission based MPG estimate of an EV discussed here is not the same as MPGe that most people consider. Check out the two links.

https://blog.ucsusa.org/dave-reichmuth/todays-electric-vehicles-can-greatly-reduce-emissions-from-driving/

https://blog.ucsusa.org/wp-content/uploads/2023/03/EV-maps-2021-data_average.png

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