How Long Does a Propane Tank Last? Grill Hours by BTU, and How to Check
A standard 20-pound propane tank — the kind that fits a gas grill — holds about 4.6 gallons, or roughly 430,000 BTU of usable energy. On a typical grill that burns 30,000 to 45,000 BTU an hour, that's about 10 to 18 hours of grilling: on the order of one to two weeks for most households, or a couple of long cookouts. The exact time is just the tank's BTU divided by the appliance's BTU-per-hour, so a small camp stove runs for days on the same tank while a big patio heater drains it in a weekend. To see how much is left, weigh the tank — a full 20-lb tank weighs about 37 lb, empty about 17 (the "TW" tare weight is stamped on the collar).
By OutletPicks Editorial 5 min read· updated 7/18/2026
The short answer
A standard 20-pound grill tank holds about 4.6 gallons / ~430,000 BTU of usable energy. Divide that by how fast your appliance burns and you get the run time:
- Grill, medium (~30,000 BTU/hr): about 14 hours
- Grill, all burners high (~45,000 BTU/hr): about 9–10 hours
For most people who grill a few times a week, that's one to two weeks per tank.
Burn time by appliance
| Appliance | BTU/hour | Hours on a 20-lb tank | |---|---|---| | Camping stove (1 burner) | ~10,000 | ~43 | | Grill, medium | ~30,000 | ~14 | | RV furnace | ~30,000 | ~14 | | Grill, all burners high | ~45,000 | ~9–10 | | Patio heater | ~40,000 | ~11 | | Fire pit | ~55,000 | ~8 |
The rule is just tank BTU ÷ appliance BTU-per-hour — a small burner sips, a big heater gulps.
How to check how much is left
- Weigh it. The empty "tare weight" is stamped on the collar as TW (about 17 lb). A full
tank is ~37 lb, so current weight − tare = pounds of propane left, and each pound is roughly
half an hour of grilling.
- Warm-water trick. Pour warm water down the side and run your hand down — the tank feels
cool below the propane line, so you can feel how full it is.
The cost per hour
A 20-lb refill runs about $20–$25 (tank exchanges are often a bit more for less gas, since they fill to ~15 lb). At 14–20 hours of grilling per tank, that's roughly $1.00–$1.75 an hour of cooking — cheap next to the food on it. Refilling at a propane dealer is usually cheaper per gallon than a swap-cage exchange, and you keep your own tank.
Keep going
Frequently asked questions
How long does a 20 lb propane tank last on a grill?
About 14 to 20 hours of cooking on medium heat, or 9 to 12 hours running all burners on high. A 20-pound tank holds roughly 430,000 BTU, and a typical grill burns 30,000 to 45,000 BTU an hour, so the time is simply the tank's energy divided by the burn rate. For most people who grill a few times a week, that's about one to two weeks per tank.
How do I know how much propane is left in my tank?
Weigh it. A standard 20-lb tank has a "tare weight" (empty weight, about 17 lb) stamped on the collar as "TW"; a full tank weighs about 37 lb, so the propane left is the current weight minus the tare, and each pound is roughly half an hour of grilling. The quick field trick is to pour warm water down the side and feel for the cool line — that's the propane level. Clip-on gauges and scales exist but the weight method is the most reliable.
How long does a propane tank last for a house?
That depends on the tank and what it feeds. A large 500-gallon home tank (filled to about 400 usable gallons) can run a house's heating for one to several months in winter, depending on climate and how much of the home runs on propane; in summer, with only a water heater or stove, it can last far longer. The math is the same — usable BTU divided by the appliances' BTU-per-hour — just at a much bigger scale than a grill tank.
Does propane go bad or expire?
Propane itself does not expire or degrade — it can sit in a tank for years and burn just the same. What expires is the tank's certification: in the US a refillable tank must be recertified 12 years after manufacture and every 5 years after that, and exchange programs swap out old tanks for you. So the fuel keeps indefinitely; only the steel bottle has a date.