How many kWh of energy are in a gallon of gasoline?

Let’s do a little energy math. I promise it won’t hurt a bit…

Dear Mike,

I read your article about the kWh of energy in a 20-lb. tank of propane. So how about gasoline? I have a 20-gallon tank of gasoline. Just how does that compare to the energy in an Electric Vehicle? —Robbie

Dear Robbie,

Great question, and once you understand how this works it’s useful for most any energy equivalency calculations.

First of all, you can google the amount of kWh (Kilowatt Hours) of energy in a gallon of gasoline. According to the EPA, one gallon of gasoline is equal to 33.7 kilowatt-hours of energy. Now we have the basic number for our calculations.

ICE (Internal Combustion Engine) calculations

To calculate the energy in a 20-gallon tank of gas all you have to do is multiply 33.7 x 20 = 674 kWh of energy.

Now, let’s assume that if an ICE vehicle gets 30 mpg, that 674 kWh of gasoline can provide 600 miles of range. So 600 miles / 674 kWh = 0.89 miles of range per kWh of gasoline energy.

If we assume $3.00 per gallon of gasoline, that will cost around 10 cents per mile if a vehicle gets 30 mpg.

EV (Electric Vehicle) calculations

My loaner Volkswagen ID.4 had a 275-mile range with 75 kWh of battery charge. So to calculate the kWh of energy needed per mile of driving we just divide 275 miles / 75 kWh = 3.66 miles of range per kWh of electricity.

If we assume $0.15 per kWh of electricity (that’s what I pay in Maryland), that works out to $11.25 per 75 kWh “tank” of electricity, and it will cost us 4.1 cents per mile for a 275 mile range.

Note that this calculation is based on a 10-hour overnight charge at your house which costs 15 cents per kWh. If you use a fast charger that only takes an hour, then you’ll be paying more like 40 cents per kWh for the convenience. And in many states if you install a smart kWh meter at your house you can save 50% on the cost of electricity used to charge your EV between 9pm and 9am.

Why the big difference?

Well, an internal combustion engine isn’t very efficient at converting gasoline energy into miles of driving. There’s a lot of waste in excess heat (notice that big radiator), as well as all that kinetic energy that’s turned into heat every time you step on the brakes.

An electric motor in an EV is much more efficient at turning electric energy into kinetic energy. Plus electric vehicles have been designed to have much lower wind resistance than their ICE counterparts.

I’ve calculated that an EV can use less than 1/4th of the raw energy of an ICE-powered vehicle. So, if there was an affordable and clean way to produce electricity locally, an EV could use a LOT less energy than a gasoline vehicle. However, that’s not the only challenge with EVs.

But what about mining all that Lithium for EV batteries?

Stand by for an update on the Salton Sea Lithium Extraction Project!

OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.

Let’s play safe out there…. Mike