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 the energy in a tank of propane compared to batteries.
I found that question over on the Rockwood Facebook group, and saw that Tony Barthel was quoting a number I must have told him about the amount energy in a tank of propane compared to a 100 aH battery.
At the time I pulled a number out of my head, which was a bit of a SWAG (scientific wild-a** guess) since I already knew the energy equivalent of a gallon of propane, but I never showed my work. So let’s see what Tony said that I said, and we’ll find out if I knew what I was talking about or if I’m actually full of bologna…
Dear Tony Barthel,
My husband and I were talking about which method is the best for heating water for dishes, showers, etc. (for the purpose of the question, imagine you have full hookups).
We’ve gone back and forth on this topic so decided we would take a poll and see the opinions of those in this group…
Depends on so many factors including where you like to camp, what your expectations are and that sort of thing. For boondocking there’s almost no choice – use your propane.
When on full hook-ups, use electric. When in a hurry and on full hook-ups, use both.
Propane has more energy than the electricity available on 30 amps (depending on what-all’s running) so you will get hot water faster using it.
Mike Sokol said that a single 20 lb. tank of propane has as much energy equivalent as one hundred 100Ah batteries. Wow. —Tony Barthel
Mike Sokol’s answer:
Tony was right in quoting what I told him, so I’m not full of bologna! My calculations show that a 20-lb. or 5-gallon (which is actually 4.7 gallons) tank of propane does contain the equivalent energy of around one hundred 100aH batteries. It’s 101 batteries, to be exact!
Here are my calculations, in case you want to win a bar bet!
- 1 Gallon of Propane = ~27 kWh (Kilowatt Hours) of electrical energy
- So 4.7 Gallons of Propane = 127 kWh of electrical energy
- A 100Ah battery x 12.5 volts = 1.25 kWh of energy
- So 127kWh / 1.25kWh = 101 Lithium batteries that can be discharged to 0% SoC
- Or 202 Lead Acid batteries that should only be discharged to 50% SoC
Tony asks a followup question…
Oh, most learn-ed one. How much would all those batteries weigh?
- One 100Ah Lithium battery weighs around 30 lbs.
- So 101 Lithium batteries would weigh 30 x 101 = 3,030 lbs.
- One 100Ah Deep Cycle Lead-Acid battery weighs around 70 lbs.
- So 202 Lead-Acid batteries would weigh 70 x 202 = 14,140 lbs.
- A 5-gallon propane tank with the same energy weighs 35.8 lbs.
I’ll take that Guinness now!
And yes, a properly poured Guinness is my favorite beer, so you can always buy me one at a bar and I’ll be a happy guy!
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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