Skip to main content

It’s a strange question, I know, but bear with me. We keep on hearing kilowatts per hour and other electric car jargon, but many people struggle putting that into simpler terms. That said, everyone knows what a gallon of gas is, and everyone is familiar with miles per gallon. Measuring electric car distance by range is great, but in terms of how much it costs to charge and electric car versus how far it’ll get you, electric cars are convoluted. Let’s compare gas cars to electric cars in terms of efficiency to see how they stack up.

Electric cars at an EV charging station in Washington, D.C.
Electric cars at an EV charging station | Drew Angerer/Getty Images

The math behind converting kilowatts of electricity to gallons of gasoline

I know, nobody likes math, but for the sake of understanding, it’s important to look at it. For starters, the energy measurement of choice for electric cars is kilowatt-hours, hence referred to as kWh. A kWh is, simply put, how many kilowatts of electricity you use in an hour. This unit of measurement is also used to determine the size of an electric car battery.

Let’s use the Tesla Model 3, which starts at $33,000, as our baseline. It comes with a 50 kWh battery, which means if you’re charging at one kW per hour, it’d take 50 hours to charge. A Level 1 charging station can supply 1.3 to 2.4 kW of electricity, fluctuating between those numbers as not to damage the battery. For a 50 kWh battery, it’d take somewhere between 20 and 35 hours to fully charge.

With the more common Level 2 charger, which supplies 3 kW to 19 kW of power at different intervals, it takes around 8 hours to fully charge the 50 kWh battery.

But kWh is only half the equation. In terms of gas, the EPA says that a gallon of gas contains 34 kW of energy. That means, if you use one gallon of gas in an hour, you’re using 34 kWh of energy. There’s a lot you can do with that information, starting with comparing the cost of kWh charging to fueling up in a gasoline car.

Comparing the costs of charging and electric car to refueling a gas car

A customer pumps premium gas into a BMW at a Chevron station in April 2006 in San Francisco
Man pumping gasoline into car | Justin Sullivan/Getty Images

The household average for electricity is around 14 cents per kW, according to Kelley Blue Book. Meanwhile, the average cost of a gallon of gas is $3.19. So let’s say you need 50 kW to get your electric car up to its maximum capacity. You’re looking at an even seven bucks. Meanwhile, seven dollars would only get you a little over two gallons of gas. And while I’m no expert, I don’t think there’s any car out there you can completely fill up with just two gallons of gas.

So, once again, the question of whether or not it’s cheaper to charge an electric car is answered. Or is it? Let’s look at the math from a slightly different angle.

As previously stated, the average gallon of gas costs $3.19 at the pump. And again, a gallon of gas has 34 kWh of energy stored inside it. But if electric car charging stations cost 14 cents per kW, that means it costs $4.76 to get 34 kW of energy. In other words, gas is still cheaper than electricity, the difference lies in that you don’t have to use as much electricity to charge an EV.

But there’s more to the question than just cost, there’s also efficiency to take into account. And as if all these numbers weren’t confusing enough, things are about to get a little more complicated.

Turning electric car range into miles per gallon

A Tesla crash in Florida involved a Model 3 similar to the one pictured here.
Tesla Model 3 | Tesla Motors

There’s a reason I selected the Tesla Model 3 and its 50 kWh battery as the base, and it’s not just because 50 is a clean number. According to Eco Cost Savings, the Tesla Model 3 is the most efficient electric car out there. But measuring electric car efficiency is a little different than gasoline car efficiency.

You already have a working knowledge of kWh, but to determine the efficiency of electric cars, we have to see how many kWh an electric car uses every 100 miles. For the Tesla Model 3, that’s 24 kWh per 100 miles, or .24 kWh per mile. Now, if a gallon of gas contains 34 kWh of energy, all you need to do is divide 34 by .24 to get how many “miles per gallon” an electric car gets.

In terms of the Tesla Model 3, that’s around 141 miles per gallon, and since it’d take about two gallons of gas to charge the electric car, that adds up to 280 miles of range on paper. Tesla says the car gets 262 miles of range, which accounts for more than our paper napkin math, but the point still stands.

So what’s the recap? Well, using electricity may cost more than using gasoline, but you don’t need nearly as much electricity to charge an electric car. Likewise, comparing how many kWh an electric car uses in 100 miles makes it possible to compare it to miles per gallon. I know, it’s all very complicated, and I hope I didn’t lose you in the numbers or math. All you need to remember is that, in the long run, electric cars are cheaper to run.

RELATED: As Electric Cars Are Built, Will Lithium Run Out?


The Most High-Tech 2021 SUVs