You’ve been hearing seemingly forever that electric cars are the future, that they are inevitable because they solve so many problems, and probably feel guilty to be driving an old, dirty, gasoline vehicle. Leaving aside the fact that there is a quite high-tech combustion technology coming down the pike, this article hopefully will help put things in context and filter out much of the propaganda you’re being bombarded with by considering some physical facts that anyone has access to.
First we need to define what “better” means. Here are a few options that we’ll discard right away:
- Electric cars are more convenient. This would be true if your definition of convenience was having to go to one of very few charging stations available today, plug in (assuming you didn’t have to wait in line), and then twiddle your thumbs for anywhere between half-hour to eight hours in order to get a charge. So clearly not true for the time being. We can discard this one.
- Electric cars are cheaper to buy. Well, the Nissan leaf is a little car that starts at around $30k in the US, the Tesla S begins at nearly $70k. There used to be tax incentives but those are expiring as we speak. Nope.
- Electric cars are safer. You can tell this to the Tesla owners who had to see their vehicles burst into flames for no apparent reason at all. Those are lithium batteries, folks, which airlines ban in checked luggage, the same as explosives and cans of lighter fluid.
- Electric cars are more powerful and ride smoother. Apparently true of the Tesla cars, probably not for the Nissan and the others. But I’d bet this isn’t the average driver’s number one criterion.
That pretty much leaves only two definitions of “better”: cheaper to operate (because electricity is cheaper than gasoline), and friendlier to the environment. I suspect the latter is the one that causes most people to put up with the inconvenience, cost, hazard, and other problems of today’s electric cars, so I’ll look into it last. Let’s look into how much it costs to fuel an electric car, compared to a gasoline car. I will use a few numbers taken from recent US statistics and other sources that appear near the top in a Google search (as of mid-August, 2018), namely:
- The overall energy efficiency of an electric car is around 70%. This is obtained by multiplying the efficiency of the motor and transmission (90%), the DC to AC inverter (95%), the battery (90%), and the charger (90%), as this article does. I think these are fairly optimistic, cutting-edge numbers.
- The average cost of electricity in the US (before taxes) is 12 cents per kilowatt-hour, from this source.
- Likewise, the average cost of gasoline in the US (after taxes) is 2.857 dollars per gallon, from this source. Using post-tax price wouldn’t be a fair comparison, since we are paying for highways through a tax on fuels that is not yet being added to electricity, but this will certainly change once electric cars become popular. To make it pre-tax we must subtract the average tax added, which this source says is 0.488 dollars per gallon. Therefore, as of August 2018, the pre-tax average cost of gasoline in the US is 2.394 dollars per gallon.
We also need an indication of how much energy needs to be spent in order to move the car, which should be the same regardless of how it is powered. Here things vary a lot, since a small car will need less energy than an SUV, so let’s pick a car. The 2018 Toyota Camry Hybrid gives 51 mpg city/53 mpg highway, per this source. Sure, it does have a battery, but the energy ultimately comes from gasoline. You didn’t expect me to compare a Tesla to a Grand Cherokee, did you? This car weighs 1700 kg (with driver) and consumes 1.500 kilowatt-hours of mechanical energy on the city-oriented FTP75 road cycle, which spans 7.45 miles, assuming a plug-to-transmission efficiency of 70% (this is because the engine regenerated during braking is smaller than one would expect, since it needs to be converted back to chemical energy in the battery). The energy requirement is 2.463 kilowatt-hours on the highway-oriented HWFET cycle, which spans 10.26 miles.
So now it’s time for some calculations. How much does it cost (pre-tax) to put the Camry through the city cycle? The number is 7.45 miles x 2.394 dollars/gallon / 51 miles/gallon = 34.97 cents. To get the number for the same car but with an electric motor, we multiply the energy required by the cost, and divide by the efficiency, thus: 1.500 kWh x 0.12 dollars/kWh / 0.70 = 25.71 cents. The all-electric Camry wins by 9 cents, which is a 26% advantage. Not bad, and I’m sure you expected it. The numbers for the road cycle are 10.26 miles x 2.394 dollars/gallon / 53 miles/gallon = 46.34 cents for gasoline, and 2.463 kWh x 0.12 dollars/kWh / 0.70 = 42.22 cents for electric. The electric is still ahead, but not by much anymore.
But most people buy electric cars because they are supposedly cleaner. They forget that electricity does not grow on trees but must be made, typically at a big, smelly power plant a few miles away from where they live. A lot of those plants burn natural gas, which makes the greenhouse gas CO2, and a lot more burn coal, which puts oodles of CO2 into the atmosphere (much more than gasoline), plus sulfur and a whole lot of other nasty stuff. How bad is it? On the right is a graph which my utility (I live in Chicago) sent me two days ago, which shows as percentages the source of my electricity. But I’m going to take the national average, computed at this source, which says that currently electricity production generates 0.55 kg of CO2 per kWh of electricity. The same source states that burning gasoline produces 8.91 kg of CO2 per gallon of gasoline.
So here’s how much CO2 the hybrid Camry puts out on the city cycle: 7.45 miles x 8.91 kg/gallon / 51 miles/gallon = 1.30 kg, and the all-electric Camry 1.500 kWh x 0.55 kg/kWh / 0.70 = 1.18 kg. The numbers for the road cycle are 1.72 kg and 1.94 kg, respectively. And here’s the big surprise: on the highway cycle the gasoline-powered car produces less greenhouse CO2 than the electric. I’ve put all the numbers on a table:
|type||city cost ($)||highway cost($)||city CO2 (kg)||highway CO2 (kg)|
There’s much to ponder here. The advantage of electric vehicles over gasoline vehicles in the categories where electrics are expected to be far superior, turns out to be fairly slim, and sometimes it actually goes the other way. It does look like electric vehicles can still be considered less costly to operate in terms of energy, but certainly not by the large margins that the media keep ramming down our throats, and not always. Certainly they are not cleaner, so far as our electricity is mostly derived from fossil sources. Think about this next time you are tempted to pay a premium to buy an electric car.