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About This Tool
Estimate how long a portable propane cylinder will power a patio heater, gas barbecue grill, camp stove, or emergency backup generator before running empty. Propane contains approximately 21,548 British Thermal Units (BTU) of latent thermal energy per pound of liquefied petroleum gas. By dividing the total available energy inside a full or partial tank by your appliance heat input rating, you can plan refuels and calculate hourly fuel burn rates.
How to Use
- 1
Enter the weight of propane inside your cylinder in pounds, such as 20 lbs for a standard barbecue tank or 30 lbs for an RV bottle.
- 2
Input the burner rating in BTU per hour from your heater, stove, or fire pit manufacturer specification plate.
- 3
Review continuous operating duration in hours and minutes alongside hourly fuel burn rate in pounds per hour.
Frequently Asked Questions
How many BTU are in one pound of liquid propane?
Commercial liquid propane yields approximately 21,548 BTU per pound (roughly 91,500 BTU per liquid gallon at standard temperature).
How long does a standard 20 lb propane tank last on a 40,000 BTU patio heater?
A completely full 20-pound cylinder contains 430,960 BTU. At a maximum continuous burn rate of 40,000 BTU per hour, the tank lasts approximately 10.8 continuous hours (about 646 minutes).
Does ambient temperature affect propane tank runtime?
Cold ambient air lowers tank vapor pressure. If heat draw is rapid on small cylinders, tank skin temperature drops and vaporization slows before all liquid fuel is consumed.
Are propane consumption calculations processed on external servers?
No. All thermodynamic fuel conversions and runtime calculations execute locally in your web browser.