How To Determine Your RV Furnace’s Propane Usage
How much propane does an RV furnace use? This is not a question you typically hear sitting around the campfire with other RVers. You are more likely to hear questions like how long will my battery last, how long will my freshwater last, or how long will my propane last. The last three questions are totally subjective, but “how much propane does an RV furnace use” has a definitive answer.
Note: This article addresses DSI (Direct Spark Ignition) RV furnaces found in most newer RVs—not older RV furnaces that contain pilot lights.
How much propane does an RV furnace use?
“Our RV furnace is rated at 30,000 BTUs, while a gallon of propane has 91,502 BTUs. This means that one gallon of propane will fuel your RV furnace for roughly 3 hours of continuous operation.” Per RVer Tory Jon
As noted in the quote above, the amount of propane used by a RV propane furnace depends on the rated size of the furnace. The larger the furnace, the more propane it will use compared to a smaller RV furnace running for the same period.
Scientists have determined a gallon of propane contains 91,500 BTUs. BTU stands for British Thermal Units. A BTU is the amount of energy required to raise one pound of water one degree F. One BTU is about the heat of a birthday candle flame.
How to calculate RV propane usage
To calculate how much propane the furnace in your RV will use, you need to look at the BTU input rating on your furnace. This information can be found on the manufacturing tag on the furnace itself or likely in the RV owner’s manual.
Here are some of the most common RV furnace sizes: 40,000 BTUs, 30,000 BTUs, 25,000 BTUs, and 20,000 BTUs. The BTU rating informs you on how many BTUs your furnace will consume per hour, as outlined here.
Once you know the BTU rating of your RV furnace, it is very easy to figure out how much propane an RV furnace uses. Take the BTU rating and multiply it by the run time, which will equal the number of BTUs used.
Example: A 30,000 BTU furnace with the burner running continuously for one hour will use 30,000 BTUs of propane or just less than 1/3rd of a gallon (30,000 BTUs / 91,500 BTUs = .328 gallons). If that furnace runs for 3 hours, it will consume almost a gallon of propane. (.328 gallons per hour X 3 hours = .984 gallons). Conversely, you can look at it this way: One gallon of propane 91,500 BTUs / 30,000 BTUs per hour = 3.05 hours of furnace run time.
Now, unless you are camping in the arctic, your furnace will not be running continuously, so you will have to adjust the math to fit your situation.
Example: A 30,000 BTU furnace that runs for 20 minutes will consume 9,900 BTUs or slightly more than a tenth of a gallon of propane. 30,000 BTU x .33 hours (20 minutes) / 91,500 BTUs per gallon = .108 gallons. Keep in mind the furnace fan will continue to run several minutes after the burner shuts down during the cool down period. During this time, no propane is being consumed.
Here’s another tip for dry campers: If you dry camp in cold weather on a regular basis and need a new RV furnace, consider over-sizing the new furnace by buying one in the next size BTU rating or two. Make sure you have adequate ducts and venting to handle the larger output.
By over-sizing, the new furnace will emit more heat for the same or just a bit more 12-volt power draw from your house batteries than the old furnace. As seasoned dry campers know, maximizing those precious amp hours in your house batteries is key.
RVers looking for valuable how-to information have learned to go to the experts. Forums such as iRV2.com and blog sites like RV LIFE, Do It Yourself RV, and Camper Report provide all the information you need to enjoy your RV. You’ll also find brand-specific information on additional forums like Air Forums, Forest River Forums, and Jayco Owners Forum.