I love to grill, smoke and barbecue. I use wood, charcoal and natural gas, depending on how I'm feeling and the task at hand. One question I hear a lot is, "How long does a propane tank last?"
This question usually refers to a propane smoker or gas barbecue and grill. I tend to keep two gas bottles, and swap them out when one runs out. I generally refill or exchange the empty in a day or two, so I always have a full tank.
But, knowing the working duration of a gas bottle is pretty useful, especially if you like to camp. Taking two bottles is a pain in the ass, so having some idea on how much cooking time you have is a good thing to know.
Actually, the answer varies depending on a number of factors, specifically the number of burners on your barbecue, or the energy consumption of the outdoor heater or gas fired appliance.
Buying a simple propane gauge can be useful, but many provide no more than a ballpark guesstimate of the contents of your propane tank. Another problem with gauges os that they can actually reduce gas flow to the burners on your barbecue.
It's pretty simple to work out, although when you first look, the calculations might appear a little daunting. Don't worry, I'll include a link to a propane tank duration calculator at the end if you want to avoid the math.
One gallon of propane gas contains about 91,500 BTU's of potential heat energy, and the BTU (British Thermal Unit) rating on most gas appliances is in BTU's per hour. This knowledge ensures that estimating propane usage is pretty easy.
Use the following formula to make the calculations:
(((91,500 × GALLONS) ÷ BTU LOAD) ÷ HOURS PER DAY) = DAYS AVAILABLE
* Gallons is the total gallons of propane available
* BTU load is the BTU rating of all appliances added together
* Hours per day is the total number of hours appliance(s) are used per day
* Days available is the estimated number of days the propane will last.
A 100 pound propane cylinder holds approximately 23.6 gallons when completely full, and an 80,000 BTU appliance that ran 24 hours a day the propane would last about 1.12 days.
(((91,500 × 23.6) ÷ 80,000) ÷ 24) = 1.12 days
If the appliance ran for 12 hours a day, the propane in the tank would last about 2.24 days.
(((91,500 × 23.6) ÷ 80,000) ÷ 12) = 2.24 days
Of course, a grill or barbecue is not going to have a BTU load anywhere near that high. A home stove, for example, has on average, around 7000 BTUs per burner. So a 4 burner stove have a potential of 28000 BTUs.
Some of the most powerful grills with steel tubular burners may have the following BTU rating.
- 25K BTU for the stainless steel burners
- 25K BTU for an infrared sear burner
- 14K BTU for a rotisserie burner
12000 BTUs is a more typical rating for a standard grill. You can use the above calculations to estimate the duration of your propane tank under various circumstances OR, use this simple online calculator to save the headache.
Keeping a spare propane tank handy is always the best bet, but if you like to get geeky with the numbers, this article should get you there.
Source: Elgas Propane Calculations