What's the Deal with MPGe?


If you’ve ever been in the market for an EV you’ve probably seen some mention of MPGe. MPGe or Miles Per Gallon [of gasoline] equivalent is used to understand an electric vehicle’s fuel efficiency. It’s how people compare those traditional gas guzzling cars to plug-ins. The more you understand about MPGe the more prepared you’ll be when it comes time to buy your EV.

The numbers and logistics can get a bit complicated, so we had our numbers guru, Adam Jones, break it down it down for us.

If you think about it differently, a gallon of fuel is simply a volume of energy that a vehicle uses to transport one somewhere. According to the EPA, 1 gallon of fuel supplies 115,000 British Thermal units (BTUs) of potential energy, and that– they say– is equivalent to 33.7 kilowatt hours (kWh) of stored electricity.

If that sounds a bit too complicated, look at it like this: one gallon of gasoline has the same amount of energy as 33.7 kilowatt hours.

1 gallon of gasoline = 33.7 kWh

So, in theory, 30 MPG means that one gallon of gas can take someone 30 miles, and 30 MPGe means that one gallon of electric vehicle power, or 33.7 kWh, can also take someone 30 miles.

All this is important to note, but at the end of the day, what really matters is two things: fuel efficiency (i.e. MPG or MPGe) and the price of fuel.

For example, let’s say we have two cars:

Car 1 (Runs on Gas):

MPG: 25

Cost of 1 gallon: $4

Car 2 (Runs on Electric):

MPGe: 100

Cost of 33.7 kWh: $16

Here’s the important part: if both cars travel 100 miles, Car 1 would need at least 4 gallons of gas at $4/gallon, so it'd cost Car 1 $16 to travel 100 miles. On the other hand, Car 2 would only need one charge of 33.7 kWh to go 100 miles, but at $16 per 33.7kWh. So, both cars would travel the same distance for the same amount of money despite Car 2 having much better fuel efficiency.

At the end of the day, you have to look first at the car's fuel efficiency, and then the price of the fuel per energy equivalency unit.

But we’re not done yet. Now lets compare the two: gas versus electric cars.

As of today, the average price of gas is $2.90/gallon.

1 gallon of gas = $2.90

On the other side, the average price of one kilowatt hour of electricity is $0.12. Multiply that by 33.7 and we have our gallon of electric fuel equivalent. So, $0.12/kWh multiplied by 33.7 kWh equals $4.04.

33.7 kWh = $4.04

Right now, according to the market, a gallon of fuel for a gas car is 34% cheaper than a “gallon” of fuel for an electric car. It appears as though things are looking good for those gas cars. This is true, gas cars have electric cars beat when it comes to price of fuel, but that’s actually not the important part, the thing we’re looking at is fuel efficiency– this is where the tables turn.

Currently the most fuel efficient car on the market soley running on gas is the 2018 Hyundai Ioniq Hybrid. It has an extremely impressive 58 MPG (combined)– double to triple what most cars on the road have. To make sure we don’t forget this impressive stat, let’s list it below:

Most Fuel Efficient Gas Car = 58 MPG (combined)

Now let’s take a look at the electric cars. So the absolute least fuel efficiency car on the market that runs solely on electricity is the Mercedes Benz B250e. Despite being the worst performing battery electric vehicle (BEV), the B250e comes in with a 83 MPGe combined. Once again, so we don’t forget this, let’s write it down:

Most Fuel Efficient Electric Car = 83 MPG (combined)

Now, if you’ve gotten to this point in the article and are still a bit confused, we’re about to clear everything up.

 Let’s compare how much it costs to drive 500 miles in both a gas and electric car. Take a look below:

Price per 500 Miles for the Most Fuel Efficient Gas Car

Average Price for Gallon of Gas = $2.90

Gallons of Gas Needed to Travel 500 Miles = 500 Miles / 58 MPG = 8.62 G

Price per 500 Miles = $2.90/G x 8.62 G = $25.00

 

Price per 500 Miles for the Least Fuel Efficient Electric Car

Average Price for “Gallon”(33.7 kWh) of Electricity = $4.04

“Gallons” Electricity Needed to Travel 500 Miles = 500 Miles / 83 MPG = 6.02 G

Price per 500 Miles = $4.04/“G” x 6.02 G = $24.32

 

The important takeaway here is this: the least fuel efficient electric car is cheaper to drive than the most fuel efficient gas car. This is just another reason why EV’s beat a traditional gas car every time.

 

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