Introduction
So how long does a propane tank last? Long enough that most grillers never think about it, right up until the flame dies mid-burger. The honest answer depends on your grill and how hard you run it. At Brooksies Patio Propane, your trusted BBQ store in Chandler, AZ, we field this question every week, so here's the real math and how to never get caught empty.
The Short Answer: 18 to 20 Hours of Grilling
A full 20-pound tank runs a mid-size gas grill about 18 to 20 hours. That's the number to remember. For most families, that works out to somewhere between 15 and 20 cookouts before you're back for a fill.
Here's the math behind it. A 20-pound tank holds roughly 4.6 gallons, near 430,000 BTU; the Department of Energy tracks propane's energy content if you want the fine print. Burn that through a 30,000-BTU grill on medium and you get close to 18 hours. Crank a big four-burner rig on high and it can vanish in ten.
Why Your Tank Empties Faster Than the Chart
Those chart numbers assume one thing: medium heat, steady. Real cooking isn't that polite. You sear on high, you preheat fifteen minutes every time, and half the burners run wide open while you crowd the grates.
Wind steals heat too, and a lid you keep lifting bleeds gas with every peek. Preheat, then dial it down. That alone stretches a tank by hours. In our Valley summers people crank everything to fight the ambient heat, honestly that's the fastest way to drain a tank before Labor Day.
Tank Size Changes the Whole Picture
Bigger tank, longer runtime. Simple as that. The standard 20-pounder covers most backyards, but a 30-pound or 100-pound tank makes sense if you grill constantly or feed a patio heater and a fire feature through winter.
Cook a lot? A spare 20-pounder or a bigger tank saves you the mid-week refill run. Matching the tank to the grill helps too, and the Phoenix grills we carry run from compact two-burners to big entertainers, so we can point you to a setup that fits how you actually cook.
How to Tell How Much Propane Is Left
Don't guess. Guessing is how the burner quits with raw chicken on the grates. Two methods actually work, and neither needs a fancy gauge.
Weigh the tank: the tare weight is stamped near the collar as 'TW,' usually about 17 pounds, and a full tank runs near 37, so the difference is your gas. Or pour warm water down the side and feel for the cool line where the propane sits. Clip-on gauges? Hit or miss, so we keep a backup tank around and suggest you do the same.
Arizona Heat and Your Propane Tank
Our heat doesn't burn propane faster, but it changes how you store it. Heat matters here. A tank baking in a closed trunk is a real hazard: pressure climbs and the relief valve can vent.
Keep tanks upright, shaded, and off scorching concrete; never leave one in a hot truck bed across town. The NFPA's propane safety guidance covers the rest in two minutes. When it hits 115 in July, don't leave the tank in the car. Same goes for the dog.
When to Refill So You're Never Caught Empty
Refill at about a quarter tank. Don't wait for empty. It's a gamble you lose on game day, so keep one full tank in reserve and rotate the two.
One more tip: a refill beats a swap cage most days, because you pay for the gas you actually get and we check the tank for rust and dings while it fills. Bring it in for a propane refill in Chandler and we'll have you back on the patio in minutes. Track your grill hours and you'll always know when you're due.
Conclusion
So how long does a propane tank last? Around 18 to 20 hours for most grills, less if you cook hot. Weigh it, keep a spare, refill before empty. Stop by Brooksies in Chandler for propane, firewood, and BBQ supplies, and we'll top you off fast.