How Long Does a 20lb Propane Tank Last?
You're halfway through a summer cookout and you hear that hollow rattle when you shake the tank. How long do you have? The answer depends on your appliance, its BTU rating, and how high you're running it. Here's a practical guide to propane burn times for the most common uses.
The Math Behind Burn Time
A standard 20-lb propane cylinder holds approximately 4.7 gallons of liquid propane. Propane produces about 91,500 BTUs of heat per gallon. That means a full 20-lb tank contains roughly 430,000 BTUs of energy.
To calculate burn time, divide the total BTUs by your appliance's BTU rating. A 30,000 BTU grill running at full blast would burn through a full tank in about 14 hours. In practice, you'll rarely run any appliance at maximum output the entire time — so real-world usage stretches further.
Burn Time by Appliance
| Appliance | BTU Rating | Estimated Hours (Full Tank) |
|---|---|---|
| Gas grill (2-burner) | 20,000–30,000 | 14–21 hrs at high; 25–40 hrs typical use |
| Gas grill (4-burner) | 40,000–60,000 | 7–11 hrs at high; 15–25 hrs typical use |
| Patio heater | 40,000–46,000 | 9–11 hrs |
| Tabletop fire pit | 10,000–50,000 | 9–43 hrs depending on size |
| Camp stove (single burner) | 7,500–10,000 | 43–57 hrs |
| Propane turkey fryer | 55,000–185,000 | 2–8 hrs |
| Portable space heater | 9,000–18,000 | 24–48 hrs |
How Long Does a Grill Tank Last for Cookouts?
For a typical backyard gas grill, a 20-lb tank will last roughly 15–20 cookout sessions if you grill for about an hour each time. That's a full summer's worth of weekend grilling for most households. Heavy users who cook outdoors several times per week may go through a tank every 4–6 weeks.
The biggest variables are burner count, heat setting, and how long you preheat. Running all four burners on high to sear steaks uses propane much faster than cooking low-and-slow with one or two burners.
Why Your Exchange Tank May Run Out Faster
If you've been getting your tanks at an exchange kiosk (Blue Rhino, AmeriGas), you may have noticed they seem to run out sooner than expected. That's because exchange tanks are typically only filled to 15 lbs, not the full 20-lb capacity. You're starting with 25% less propane than a full refill. See our full breakdown in Propane Exchange vs Refill: Which Is the Better Deal?
How to Tell When Your Tank Is Getting Low
There are a few ways to check your propane level without a gauge:
- The shake test: Pick up the tank and shake it. An empty tank sounds hollow; a full one has a sloshing weight to it.
- The hot water trick: Pour warm water down the side of the tank. Run your hand along the metal — where it turns cool is the propane level. The liquid propane absorbs heat from the water, making that section noticeably cooler.
- A propane gauge: Inline gauges ($10–$20) screw between the regulator and the tank valve and show an analog level reading. Worth the investment if you grill frequently.
- Weighing the tank: Most 20-lb cylinders weigh about 17 lbs empty. If your full tank weighs 37 lbs, you have a full load. Weigh it periodically to track usage.
Tips to Make Your Tank Last Longer
- Preheat for only 10–15 minutes instead of letting the grill run idle
- Keep the grill lid closed while cooking to retain heat
- Use only the burners you need — one or two for smaller cooks
- Check connections for leaks (brush soapy water on the valve; bubbles mean a leak)
- Store tanks in a cool, shaded area — heat causes the pressure relief valve to vent propane
When It's Time to Refill
Don't wait until you run out mid-cook. When your tank feels noticeably lighter or your grill's flame starts to sputter, it's time to head to a refill station. Find one near you on our Propane Locations Map, or browse city pages for Houston, Dallas, Austin, San Antonio, and beyond.