Authors Note: This article has many footnotes that provide additional context. Please see these for a more comprehensive understanding of the discussion at hand.
There is a popular myth about electric vehicles (EVs) that refuses to die, and it’s about time we start digging the grave. It’s usually presented something like this: “Electric cars don’t actually reduce emissions, they just offset the emissions to the power plant.” Half of this statement is true, and half is not. It is obviously true that EVs offset the emissions to the power plants, but the first half of the statement—that moving emissions to the power plant doesn’t reduce emissions—is not. Let me explain.
The typical counter-argument goes something like: “Sure it moves the emissions to the plant, but that’s not true if the EV is getting its power from clean sources.” This is a fine point, and we will return to it again later, but this inevitably leads into a conversation about the praises and failings of renewable energy. This almost always inevitably devolves into two bulls butting heads, with one side screaming “Yes renewables!” and the other saying “No renewables!” But take a second to notice that this is no longer even the same argument that was originally raised. The conversation almost always quickly becomes about energy production, not EVs.
In truth, there is a far better counter-argument to the original statement, one that fundamentally dismantles the point being conveyed without even mentioning alternative energy sources. It is the following:
Even if EVs relied solely on power plants that only burned gasoline, they would still produce fewer emissions than gas cars.
This seems like a bold statement, so I will spend this article backing up this argument. In the end, it boils down to energy efficiency. Internal combustion vehicles (ICVs) are incredibly inefficient, while power plants are as efficient as possible (millions of dollars go into improving the efficiency of power plants by a fraction of a percent), and transferring electricity is generally a highly efficient process. Think of how hot your car’s engine gets after driving for just a few minutes—literally hot enough to cook food on. Well, heat is just a form of energy. Keeping this in mind, a perfectly efficient vehicle would produce no excess heat, as 100% of the energy would go into spinning the wheels. Viewed from this perspective, the heat an IC engine creates is literally wasted energy that should’ve gone into moving the car, that didn’t. If your cars engine only has 25% efficiency (as is typical), then that means only a quarter of the gas you put into your car actually goes into moving it forward – think about all the wasted money!
Because of the comparatively higher efficiency of turbines in power plants, coupled with the very efficient process of moving electricity, it turns out that EVs produce fewer emissions even without utilizing large quantities of clean energy. To demonstrate my point, I’ll do the math below. The calculation is more complex for the EV: While for an IC engine you simply need the engine efficiency, for an EV you need the efficiency of power generation, transmission, charging, and the motors that drive the car. All of these factors are given below:
Efficiency of a IC engine1: 25%
Efficiency of a Power Plant2: 40%
Efficiency of electricity transmission: 95%
Charging efficiency: 90%
Motor efficiency: 90%
To calculate EV efficiency with these factors, the formula is the following:
Power Plant x Transmission x Charging x Motor = XX%
40% x 95% x 90% x 90% = 30.8%
Thus, the efficiency of an EV is around 31%,3 while an ICV is only 25%.
But how does this hold up in the real world? After all, the reality is that coal (which remains the dominant fuel around the world, providing over 1/3rd of global electricity) does release more greenhouse gas emissions per unit of energy than gasoline. While gasoline at the pump has a carbon intensity of 67 Kg (150 pounds) of CO2 per million Btu4, bituminous coal (the most common type used for power generation) has a carbon intensity of 93 Kg (205 lb) CO2/million Btu — 40% greater than gasoline. Because of this disparity, in theory regions with exceptionally high coal use can be an issue in terms of EV emissions, but as we will see in a minute even this almost never holds water in the real world.
So now that the theoretical proof has been laid out, let’s take a look at the real world. We will start by taking two cars, again one EV one ICV, and assume that each of them uses 1 million Btu to move the vehicle. Which would have produced more carbon? To factor in efficiency, we can calculate the total energy that must have been produced to get an end result of 1 million Btu. Once this is calculated, we can multiply the total energy consumption by the carbon intensity of each fuel. The math looks like this:
1,000,000 Btu/Vehicle Efficiency = Total Energy Use (in Btu)
↪Total Energy Use * CO2 Intensity = Total CO2 Emissions
Now I will do the math to show emissions of a conventional gas vehicle, an EV powered only by gasoline, an EV powered only by coal and an EV powered by the current US grid, which has a carbon intensity of roughly 21 Kg CO2/million Btu.5 The math looks like this:6
Conventional Gasoline Vehicle
1,000,000 Btu/25% = 4,000,000 Btu
↪4,000,000 Btu * 67 Kg CO2/1,000,000 Btu = 268 Kg CO2
EV Powered by Gasoline
1,000,000 Btu/31% = 3,225,806 Btu
↪3,225,806 Btu * 67 Kg CO2/1,000,000 Btu = 216 Kg CO2
EV Powered by Coal
1,000,000 Btu/30.8% = 3,225,806 Btu
↪3,225,806 Btu * 93 Kg CO2/1,000,000 Btu = 300 Kg CO2
EV Powered by US Grid
1,000,000 Btu/30.8% = 3,225,806 Btu
↪3,225,806 Btu * 21 Kg CO2/1,000,000 Btu = 68 Kg CO2
As this data shows, an EV powered just by gasoline actually produces lower carbon emissions than a regular ICV. Additionally, when we look at the most pessimistic scenario, even the EV powered only by coal has emissions just 11.3% greater than the ICV—a difference which would actually become even smaller once efficiency losses from extraction, transport and distribution are taken into account since power plants are much more centralized (and thus efficient in this case) than gas stations. But the most important comparison to make is that of the real world, between an ICV and an EV on the current US power grid. In this scenario there is absolutely no competition, with the EV creating just one-fourth the CO2 emissions of an ICV.
Both in theory and reality, EVs are almost always the better environmental option. Even having just 10% clean energy on a 90% coal powered grid puts EVs on par with gas guzzlers. Indeed, a 2020 study in Nature found that EVs would already produce lower emissions for 95% of global road transport. Unless you live somewhere where the soot from burning coal creates a thick layer of black dust over your community on a daily basis, it is safe to assume an EV is the more environmentally friendly choice. Even then, it is probably still better to get an EV, because your electricity almost certainly contains power from other sources in addition to the coal plant.
And it’s not just carbon emissions that this applies to. ICVs pollute the air of the neighborhoods they operate in with various types of localized air pollution, with a 2018 PNAS study finding that road vehicles contribute 28% of PM2.5 pollution (the most important and severe type of air pollution) in the US, leading to approximately 30,000 premature deaths in the year studied. As I discussed in my article The Five Hundred Million Club, air pollution is arguably a larger societal problem than climate change itself. But EVs offset this pollution not just by creating less of it, but by offsetting the pollution outside of the city where people live. It may not be gone, but EVs both reduce the mass of the problem, and move what is left to a safer location.
In summary, what have we learned? EVs (nearly) always come with lower emissions. This is true to the extent that even if EVs got their power from a power plant burning gasoline they would still generate fewer emissions than a traditional gasoline-fueled car. The very low tailpipe emissions using the current US grid compared to an ICV is evidence enough to support the transition. Of course, this is only one advantage of several that EVs bring, which I hope to elaborate on in future articles. Other arguments remain; resource conflicts, charging accessibility, and range anxiety being the top ones. Be assured, all of these arguments have fatal flaws just like the one this article discussed, but they will have to be addressed another day. Electric cars are here to stay, and by embracing them, working to resolve the problems that they do have, we can create a brighter future. Electric vehicles are not just a part of a clean future; they are a driving force towards it.
IC engine efficiency can vary greatly, with a common range being 11-27% (as noted in the study linked), but the most commonly cited numbers trend between 20-25%. Also important to note is that diesel engines have higher efficiency (25-37%), but I focus on gasoline vehicles in this article. In any case, the conclusions at the end of this article still apply to diesel engines when looking at real-world grid fuel compositions.
Power plant’s do not use gasoline. However, they can use coal, natural gas, diesel, and less-refined oil. Real-world efficiencies for these vary for technical reasons, with a common range estimate being from 32-45% efficiency depending on the plant, fuel and location. The most common efficiency for power plants is typically cited at around 40%, which is what we will use here.
Be careful if you go online to check this figure, as the numbers you will get generally do not include the efficiency of the power plant (which is disingenuous to the reality of the situation in my opinion), only factoring in charging and motor efficiency.
British Thermal Units – A common metric used to measure energy.
Because carbon intensity of power grids is measured in CO2/MWh and not CO2/Btu, this figure is an estimation based on the current US grid, which is roughly 20% Coal (93 Kg CO2/million Btu), 40% Natural Gas (53 Kg CO2/million Btu), and 40% clean sources (nuclear, hydro, wind, solar, geothermal). The clean sources are assumed to have a carbon intensity of zero for this calculation, which is fair because we have focused purely on emissions from power generating thus far, ignoring emissions from extraction, manufacturing, and construction.
Keeping this in mind:
(93 Kg CO2 * 20%) + (53 Kg CO2 * 40%) + (0 Kg CO2 * 40%) = 21 Kg CO2/million Btu
These numbers shouldn’t be taken literally for reference – I rounded all numbers to the nearest whole number and made several simplifications. Additionally, there are several elements to this which are highly regionally independent (such as the efficiency and fuel type of any specific power plant). Most importantly, this article has studied only the “tailpipe” emissions between EVs and ICVs, and not the cumulative life-cycle emissions. EVs are still better when it comes to their lifecycle emissions, but they do produce far more emissions during battery manufacturing. In any case, while the precise numbers here should not be cited, the general comparison remains accurate enough for discussion and policy.