By Russ and Tiña De Maris
Here’s a question worthy of posting on an Internet RV forum: “How much propane will a 15,000 btu RV furnace use in a day?” The question got posted – and it was certainly legitimate enough, but not a soul offered to render an opinion. Perhaps the safest might be: “Too much!”
“How much money will you spend to heat an RV?” is a frequently heard question when the cold weather rolls around and people think about getting away from the house and back to the great outdoors. Sad to say, the question is on a par with, “How much wood could a woodchuck chuck?” There are so many variables: How big is the RV? How well insulated? How cold is it outside? How warm do you want to keep the inside? What size is the furnace — or are you even heating with a furnace?
Here’s a scenario: A couple in Quartzsite, Arizona, were bemoaning how cold a winter trip had been. They have a 40-foot trailer, and based on an eight-day propane consumption history, they came to a nasty conclusion: Using their trailer’s furnace, it would cost them nearly $170 a month to heat if things stayed the way they were over the “trial period.” Needless to say, adjustments had to be made.
How much propane can you use? For them, their furnace is rated at 40,000 btu input, and a 31,000 output. A little math and a little propane background will help. A gallon of propane will supply 91,500 btu. Run their furnace a little over two hours and 15 minutes, and a full gallon of LP is burnt. Put another way, at $2.32 a gallon, for every hour of operation, $1.02 is spent. To add to the insult, 23 cents of that $1.02 is simply “thrown out the window” due to heater inefficiency — if you lived in a perfect world. But by the time you account for heat loss from ducting the heat throughout the rig, the dollars thrown away in this system are almost too painful to contemplate.
The couple finally resorted to closing off the areas of the rig when not in use, keeping the thermostat set at a chilly 50 degrees at night, and running an electric space heater in the areas being used, keeping the fuel hog furnace for use in heating the place up in the morning.
It’s no wonder that many RVers have opted out of using their rig’s factory furnace. Often they use alternative propane heaters: Blue flame, catalytic, or “brick” heaters. Nearly all models of these units are “unvented” meaning they are not connected to the outside. Almost 100 percent of the energy they consume in the form of propane is turned into heat. Keep in mind, to be safe you’ll need to keep a window or vent cracked to bring in oxygen, which translates to a heat loss itself. However, the efficiencies are higher and the equivalent amount of LP used is much less than a built in furnace.
There are other considerations: Putting 100 percent of the heat into the RV also means 100 percent of any combustion byproducts. There’s a whole world of controversy among RVers about just how safe or unsafe unvented heaters are. To that end, if you decide to use an unvented heater, ALWAYS follow the manufacturer’s instructions to the letter. We shop for heaters with oxygen sensors — these will shut down the heater in the event the amount of oxygen in the RV gets so low as to present a health threat. We also insist on having a working, frequently tested, carbon monoxide alarm in the RV.
How much LP will you burn with an alternative heater? When it comes time to refill your LP cylinders, no doubt you’ll moan, “Too much!” but it’ll certainly be less than with your monster furnace.