No, a BMW 7 Series is not kinder to the atmosphere than a Tesla

An attorney from Philadelphia, Power Line reader Martin Karo, wants you to know that Tesla drivers are smug, fact-averse liberals whose cars are worse for the planet than their gas-burning counterparts. It's something people feel the need to do from time to time, and it doesn't seem to be from a place of genuine concern for the environment. Nor does it usually tell the whole story, just the part that's convenient. Then it gets repeated. How many times have you heard someone say that a Hummer is greener than a Prius?

Which brings us to the recent post on the Power Line political blog. The editor warns us at the beginning that "there will be math." And boy is there. But first Karo takes a minute to insult Tesla owners (he describes them as condescending, but then uses gratuitous Latin in the next sentence). His conclusion: "Liberals frequently care more about feelings than facts, and your smug Tesla-owning frenemy will never admit it, but in day to day usage, the big BMW [740i] is actually 18-percent more efficient, and 18-percent kinder to the planet."

His math, though, is way off. It's a little hard to get through, but that's probably the point. If it's convoluted enough, it doesn't have to be complete, just convincing. Unfortunately, Karo's efficiency calculations include the distribution lifecycle for electricity, but not for gasoline. That is, he calculates how much energy it takes to get electricity to your car, but treats gasoline as if it shows up at the pump with no other energy used. He does no further calculations to support his "kinder to the planet" statement.

Karo starts by pointing out that much of our electricity comes from hydrocarbon fuels, which is true. If you live in the US, your energy mix is on average about 33 percent natural gas, 33 percent coal, 20 percent nuclear, and 13 percent renewables, according to the EIA (this is the same source Mr. Karo cites). Petroleum makes up one percent of it.

Karo treats this mix as its petroleum equivalent in terms of electricity generation, and throughout his post also confuses petroleum (used for generating electricity) with gasoline, referring to both just as "gallons." In truth, they hold different amounts of energy: "petroleum" in the electricity mix generates 13.76 kWh per gallon, while US gasoline is about 33.7 kWh per gallon according to the EPA.

So, when Karo calculates that a Tesla uses 678 kWh (including parasitic losses and battery/cabin heating), or his misleading figure of 49.28 gallons to travel 1000 miles, that actually equals 20.12 gallons of gasoline using the EPA's equivalency. That's 49.7 mpg when you include transmission and charging inefficiencies, if you accept his 678-kWh conclusion. It's considerably less than the Tesla Model S's EPA ratings of anywhere from 89 to 105 MPGe combined, but still more than the BMW 740i (at 24 mpg combined) he uses for comparison.

Also his comparison is misleading. Basically he's trying to compare apples to apples, when he should be comparing apples to oranges (or refraining from false comparisons altogether).



Gasoline doesn't just magically appear at the pump. Karo goes through all the trouble to calculate the efficiency of electricity transmission, but compares that power plant-to-wheel figure to the final petroleum product, as though there's not "many a slip 'twixt the cup and the lip" (his words) in turning stuff buried underground into usable fuel. It takes resources ­– including electricity and more fossil fuels – to extract, refine, and transport gasoline and diesel. In a true comparison, well-to-wheel lifecycles don't just apply to one form of energy, but not the other.

And environmental problems aren't caused by consumption. They're caused by emissions. Consuming 500 kWh worth of gasoline produces much more greenhouse gas emissions than consuming 500 kWh worth of solar energy. Even when you take into account the lifecycle greenhouse gases of solar energy, the impact of using "renewable" energy ("clean" or "cleaner" energy is a better term, as the issue isn't about supply) isn't the threat to our planet and health. Pollution and greenhouse gases are the problem.

So here's some math involving emissions.

Now, burning – just burning­, not extracting, refining, or transporting – a gallon of gas emits 19.64 pounds of CO2. Corporate average fuel economy has been basically flat at 25.1 mpg since the 2014 model year. That means the average car emits 0.7825 lbs of CO2 per mile. The BMW 740i Mr. Karo mentions produces 0.8201 pounds per mile. That's not wheel-to-well. That's gasoline-out-of-thin-air figures.

The Tesla Model S 100D goes 3.35 miles per kWh. That's 0.6179 pounds of CO2 per mile if the energy mix were 100-percent bituminous coal.

So let's compare apples to apples, from seed to plate. The EPA says that in the US, the average electricity mix produces 1.2254 pounds of CO2 per kWh delivered, including 7.3-percent transmission losses. Giving Mr. Karo the benefit of the doubt, let's say his 10-percent distribution loss is accurate. That's 1.2628 pounds per kWh, or 1.4856 pounds per kWh inside the battery using Karo's 85-percent efficiency figure. At 3.35 miles per kWh, that's 0.4435 pounds of CO2 per mile.

Wheel-to-well emissions of E10 gasoline at 26 mpg are more than double that, at 0.948 pounds of CO2 equivalent per mile. So, if you actually care about the environmental impact of your driving more than meaningless false comparisons, you're better off driving a new Model S than that new Bimmer.

Mr. Karo is right about one thing. Teslas (and EVs in general) have their problems. They certainly do contribute to atmospheric emissions using electricity from the grid, as we've shown. EVs are a part of the transition away from dirty energy, even if the energy isn't entirely clean yet. But our capacity to produce renewable energy has been growing and will continue to grow, even if federal policy under Trump slows it down.

Another major, and fair, criticism of electric vehicles focuses on the materials they require. We have to extract lithium and rare metals that go into batteries and electric motors from the earth. There can be high environmental and human costs associated with mining and refining these materials, and while methods are improving, growing demand of a finite resource doesn't bode well unless we figure out a solution. Battery recycling, for one, shows promise.

People a lot smarter and with more resources than me or Mr. Karo have done more accurate and holistic calculations than we ever could, and they repeatedly determine that EVs have a lower environmental impact than ICE vehicles. Yes, even when you factor in manufacturing. Rest assured that EV owners think about their environmental impact. Just because some Tesla owners are smug boors doesn't automatically make them wrong. And an equally smug response with selective math is not much of a counterpoint.

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