It's Still Cheaper To Drive 100 Miles In An Electric Car

Some back of the napkin math easily proves this to be true.

Chevrolet Bolt EV/Bolt EUV Chevrolet Bolt EV/Bolt EUV

Recently, Jalopnik published an article boasting that “Driving 100 Miles in an EV Is Now More Expensive Than in an ICE.” That would be a very interesting update if it were generally true. I heard a similar argument from a Boston EV group recently, so this has really piqued my interest.

Let’s consult the back of an envelope to check the math on Jalopnik’s claim.

For level-setting purposes, we can start with the following variables in Boston, a metro with some of the highest U.S. energy prices.

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● Fairly average EV efficiency of 3 miles per kilowatt hour (= 33.3 kWh to drive 100 miles)

● Boston’s average electricity price is 26 cents per kwh

Charging from home is the cheapest and most common option, so we’ll assume that’s what’s happening. Given the Boston electric prices, it would cost $8.66 to travel 100 miles. I don’t happen to live in Boston, and neither do any of my coworkers at Recurrent, so let’s use average energy costs to look at 100 miles for some of our team members.

● Winston-Salem: 11 cents/kWh = $3.67 to drive 100 miles

● Des Moines: 13 cents/kWh = $4.32 to drive 100 miles

● Seattle: 13.37 cent/kWh = $4.45 to drive 100 miles

● Dallas: 14.77 cents/kWh = $4.92 to drive 100 miles

● Cleveland: 15.25 cents/kWh = $5.07 to drive 100 miles

For level setting the gas car variables, let’s pick a Toyota Corolla which gets 35 miles per gallon combined. For simplicity’s sake, we’ll stay away from hybrids.

● 100 miles would be 2.86 gallons (100 miles/ 35 mpg)

● Boston’s current gas price is $3.43 average

That would be $9.82 per 100 miles with the ICE vehicle, compared to $8.66 with the EV. Close, but driving the EV is still cheaper.

There is also some weird accounting in the Jalopnik article, too. This paragraph tries to factor in the externalities of using a public charger, but not the externalities of gas-powered cars, themselves.

“The massive increase in the report for charging station users versus home chargers is accounted for by the deadhead miles to reach stations and the opportunity cost of waiting for vehicles to charge at stations. The difference highlights the lackluster coverage for electric vehicle charging infrastructure across the United States.“

While technically, there is a “cost” for waiting for a charger, there are also definite, measurable costs that come from gas cars: air pollution, oil extraction and refinement, and the societal impacts of climate change. You can’t include the larger issues of charging without including the full picture on gas.

I’m eager to hear your thoughts in the comments. But, as a scientist by training, there is a way to be even more precise about these calculations. Feel free to skip or read on for this addendum on charging efficiency.

No EV chargers are 100% efficient in getting electricity from the grid to the car battery. If we’re being very conservative, we can guess that the typical Level 2 home charger (208-240V) is 90% efficient. A person is charged for the electricity measured at the meter, not what actually goes into their vehicle. Assuming 90% efficiency, it actually takes 1.11 kWh to get 1 kWh into the car’s battery.

1. With this in mind, we could revise the Boston area numbers above:

a. 100 miles at 3 kWh/mile would need 33.3 kWh from the battery.

i. 33.3 kWh into the battery would require 37.0 kWh from the wall using an L2 charger assuming a 90% efficiency.

ii. 37.0 kWh would cost $9.62 at 26 cents/kWh.

iii. The Corolla ICE at 35 mpg combined would need gas prices to be $3.37 for cost parity.

b. 100 miles at 3.57 kWh/mile would need 28.0 kWh from the battery (this is the EPA efficiency for a Chevrolet Bolt)

i. 28.0 kWh into the battery would require 31.1 kWh from the wall.

ii. 31.7 kWh would cost $8.09 at 26 cents/kWh.

iii. The Corolla ICE at 35 mpg combined would need gas prices to be $2.83 for cost parity.

Since the current price of gas in Boston is higher than $3.37, even when factoring in charging efficiency, an EV is still cheaper. And, this doesn’t account for any clean driving promotions offered by Boston utilities, or discounted charging offered by the city or EV manufacturers (such as plans with Electrify America).

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