Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM. Today I discuss how many kWh are in a gallon of gasoline and the energy equivalency of different sources.
I saw your article last week 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
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
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 $4.00 per gallon of gasoline, that will cost us around 13.3 cents per mile if your vehicle gets 30 mpg.
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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.
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 found that an EV can use less than 1/4th of the raw energy of an ICE-powered vehicle. So, if there was an affordable way to convert natural gas into electricity, then transport it where it’s needed without too much efficiency loss, an EV could use a LOT less energy than a gasoline vehicle.
But is this possible? Stand by for more energy science in a few weeks.
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….
Send your questions to me at my new RVelectricity forum here.
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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