I have an 18,000BTU/hour BigBuddy propane fire and a 23,000BTU/hour Kerosene heater that I use for quick and supplementary heat. A gallon of KleanStrip or 1K Kerosene should last about 6-7 hours by the math and that feels about right based on experience. A 15lb fill of a 20lb propane tank should last 16 hours with the propane heater at full blast, but generally I use the BigBuddy unit turned down to a low or medium setting. Propane is cheaper for me costing about a 90c/hour at max burn with the Kerosene heater at $1.6/hour. The propane heat is cheaper even when you account for the somewhat larger output of the Kerosene heater.
Cost breakdown for the Propane and Kerosene I use
I’m buying barbecue grill propane refills from big box stores for ~$15 and assuming a 15lb load (not 20lb) and paying $11 for gallon packs of 1K Kerosene or KleanStrip. I used a heat content of 135,000 BTU/gallon for Kerosene and 21,500 BTU/pound for propane. The two heaters have about the same rating (18 & 23,000 BTU/hr) but the true heating cost relates to the fuel price and heat content of the fuels not the output of the heaters. I could probably knock down that Kerosene price by shopping for ‘draught’ low sulfur 1K Kerosene (that’s NOT diesel!) with my own container at the right store or gas station. They’d be equivalent at about $6.30/gallon for 1K Kerosene but right now it’s not worth the effort, given that I’m only burning about 5 gallon as supplementary heating with three-season cabin usage. It’s more convenient to have the sealed containers avoiding water contamination and any fuel degradation from air exposure.
The 1lb Coleman propane tanks are way expensive
The 1lb disposable ‘Coleman’ cans run $3.5 to $5 compared to a Dollar for a pound of fuel in the barbecue size 20lb propane tanks. That makes them pricier than the pre-packaged Kerosene. I had bought an adapter to refill the disposable 1lb cans from a 20lb grill-sized propane cylinder. I don’t recommend this as a long term option: You have to flip over the barbecue tank in order to add liquid to the lantern cylinder (right ways up transfers gas), then you find that a proportion of the refills start to leak. I don’t even recommend doing the refills of the disposable cans as a short term option, but I see FlameKing has a refillable 1lb-alternative that is maybe handy to have around if you have propane fired lanterns for emergency light.