Thursday, September 21, 2023


Fact or Fiction? Liquid propane expands 270 times when released into the atmosphere (ANSWER)


It’s hard to imagine one gallon of liquid propane (LPG) expanding to 270 gallons of propane vapor when released from the LP tank (motorhomes) or cylinder (towables) of your RV, but it’s true.

“When propane vapor expands as the pressure is reduced, it expands in all directions, and quickly. Its expansion rate is approximately 270 to 1, which means 1 gallon of liquid propane in the tank will expand to 270 gallons of propane vapor when it boils (vaporizes).” Per this comprehensive article by the late Gary Bunzer, the RV Doctor.

Energy-dense propane is an ideal fuel for RV appliances

The fact that one gallon of LPG (liquified petroleum gas) can expand into 270 gallons of vapor makes it an ideal fuel for RV appliances. One of the best examples of the benefits of the energy density of propane is powering an RV absorption refrigerator as this exchange between RV Electricity’s Mike Sokol and JP, an reader, illustrates.

“Dear Mike,
I’m curious just how much battery power is needed to equal a 20-lb. tank of propane? For example, my 3-way fridge can run for a few weeks on propane mode, but when I try to power it from my batteries and inverter, it won’t even last a day before the battery is dead. Can you explain why this happens? —JP”

“Dear JP,
Ah, yes, it’s the energy density thing. And while modern lithium batteries can store a lot of power, they pale by comparison with a tank of propane. Let’s compare by first calculating how many kWh (Kilowatt Hours) of energy is in a gallon of propane. You can easily look up that the available energy in 1 gallon of propane is equal to 27 kWh of electricity.” *Note: There are approximately 4.6 gallons of propane in a 20-lb. tank.

Mike goes on to do the math providing the answer to JP’s question:

“It would take 200 lead-acid batteries of 100 Ah capacity each to equal the energy in a single 20-lb. tank of propane. Similarly, for lithium batteries, we see that 120,000 Ah / 1,200 Ah = 100 lithium batteries of 100 amp-hrs each to equal one 20-lb. tank of propane energy.” Mike sums it up by stating, “It will be a long time before there’s a battery no bigger than a propane tank that can store 120,000 Wh (watt hours) of energy.”

All-electric RVs

At this point, you might be realizing the impracticality of those promoting all-electric RVs. Why would you want to haul around 100 or 200 batteries, or fewer batteries and a way to keep them charged, to power your refrigerator, water heater, and stovetop/oven, when a compact cylinder of propane can do the same job? As Mike points out in the mentioned article, once fuel cells are perfected and affordable, propane energy will likely be the solution to electrically power your air conditioner, too.

Propane Cylinder
One tank of propane contains a huge amount of energy photo

I will close with these words of wisdom from Gary Bunzer’s article mentioned above: “The bottom line is propane can be compressed to a liquid, can be stored easily, and is relatively safe, making it the perfect fuel for use in a motorhome.”

Hopefully, this month’s installment of Fact or Fiction has taught you something new about propane while emphasizing why it is the best choice of energy for RVs.

Click here to learn more about liquified petroleum gas, how it works and why propane vapor is the logical choice for gas stoves, cooktops, ovens, gas heaters, fireplaces, and gas hot water systems.

Dave will be speaking at the 2023 America’s Largest RV Show in Hershey, PA, September 13th – 17th. He would love to meet readers that will be attending. Feel free to introduce yourself at one of his seminars.

Wow! Those attending Dave’s Dry Camping Tips and Tricks seminar (10 a.m. daily) can enter to win a soft start device. One given away daily!

Previous Fact or Fiction column:


Dave Helgeson
Dave Helgeson
Dave Helgeson has been around travel trailers his entire life. His grandparents and father owned an RV dealership long before the term “RV” had been coined. He has served in every position of an RV dealership with the exception of bookkeeping. Dave served as President of a local chapter of the RVDA (Recreational Vehicle Dealers Association), was on the board of advisors for the RV Technician Program of a local technical college and was a board member of the Manufactured Home and RV Association. He and his wife Cheri operated their own RV dealership for many years and for the past 29 years have managed RV shows. Dave presents seminars at RV shows across the country and was referred to as "The foremost expert on boondocking" by the late Gary Bunzer, "The RV Doctor". Dave and his wife are currently on their fifth travel trailer with Dave doing all the service, repair and modifications on his own unit.


  1. Well, absorption refrigerators are simple, but not the most efficient, and with reasonable solar, you can easily power a much more efficient compressor refrigerator. But, yes, you can’t touch the energy density of liquid hydrocarbons.

  2. Any gas will expand to fill the available space. It uncontained in a vessel it will expand throughout the atmosphere. Considerable more than x270.


Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Sign up for the

RVtravel Newsletter

Sign up and receive 3 FREE RV Checklists: Set-Up, Take-Down and Packing List.