By Mark Polk
RV Education 101
Have you ever planned a remote camping trip and wondered how long the propane in your tank would last before you need to head to the nearest propane fill station?
There is a way to roughly calculate your propane usage, but it’s probably best if I start by explaining how some of this stuff works in the first place.
What is a British thermal unit, or Btu? Btu is the term used to measure heat energy. It takes 1 Btu of heat to raise the temperature of 1 pound of water 1 degree Fahrenheit. LP-gas (liquefied petroleum gas) weighs 4.24 pounds per gallon and there are 91,502 Btus per gallon, or 21,548 Btus per pound.
With this basic information let’s take a look at my top 7 tips for calculating propane usage.
1. First you need to know how much propane is in your RV when the tank is full. Remember, an RV propane tank is full at 80 percent of its capacity to allow for expansion. Wait until the propane tank is nearly empty, and when you get it filled ask the attendant how much gas it took to fill it.
2. Next, multiply your propane container total capacity using one of these formulas, depending on whether you are using gallons or pounds:
- Btus per gallon equal 91,502
- Btus per pound equal 21,548
3. This will give you the total container Btu capacity. For example: If your RV propane container holds 14 gallons of LP-gas when it’s full, multiply 14 X 91,502. The result is 1,281,028 total Btu capacity.
4. Determine the total Btu demand for the LP-gas appliances you plan to use. Btu appliance demand can usually be found on the appliance itself, or in the appliance owner’s manual.
5. Now divide your container BTU capacity by the total Btu demand.
6. The outcome of #5 will give you an idea of how long you can expect your LP-gas to last. Let’s say, for the sake of an example, the total Btu demand you plan to use will be 43,800 Btus. In this case you would have approximately 29 hours of use.
7. However, keep in mind that the amount of LP-gas in the container and varying temperatures affect these calculations. This is especially true in cold weather. In below-zero temperatures the per-hour container Btu capacity will be reduced by 50 percent or more.
Calculating propane usage can give you general idea of how long you can use your LP-gas-fired appliances before needing to find a propane filling station.
|RV expert Mark Polk owns RV Education 101, a North Carolina-based company that produces and sells educational videos, DVDs and E-books on how to use RVs. Mark has more than 30 years of experience in RV maintenance. He retired from the U.S. Army in 1996 as a Chief Warrant Officer Three, specializing in wheeled and track vehicle fleet maintenance operations. He and his wife, Dawn, started RV Education 101 in 1999. They travel with their two boys in a 35-foot Type A motorhome.