How Long Does A 20lb Propane Tank Last On A Grill

Grilling can be one of the best and most enjoyable ways of cooking. You’re outdoors, the sun’s shining (hopefully), food’s sizzling, and there are no pots and pans to clean. And then the unthinkable, no sizzle, no flame, no propane.

In general, a 20lb propane tank will give you about 18-20 hours of grill time, depending on how you’re cooking and how big and powerful your grill is. And 20 hours sounds like an eternity until your flame sputters and dies. 

If you always have a spare tank on hand then I salute you and your preparedness. For the rest of us, let’s further explore how long a 20lb propane tank will last so we’re never caught in such a nightmare situation again.

Your Grill’s BTUs And Its Effect On Propane Usage

How long a 20lb propane tank will last depends largely on the size and power of your grill, as well as how you use it. 

As you may suspect, a large 4 burner grill will go through propane much faster than a single burner camp stove.

The reason for this is all about BTUs, or how much heat and energy your grill is producing. BTU stands for British thermal unit. Now, I’m no physicist so I won’t be dissecting energy transfer, but 1 BTU is the amount of energy required to raise the temperature of 1 pound of water by 1 degree.

In general, grills are measured by their BTU output per hour. There are small, single burner grills that produce less than 9,000 BTUs, and larger more powerful options that put out close to 50,000 BTUs. 

And while 50,000 may sound like a lot, it pales in comparison to a 200,000 BTU wok burner.

All that is to say, BTUs rely on propane to produce heat. So, more BTUs = More Power = More Propane Usage.  

How To Calculate Your Grills “Burn Rate”

Gas grill with white tank on outdoor patio

Now that we know that more BTUs burn through more propane, let’s figure out how much propane your grill goes through per hour. We call this the burn rate.

The magic number to remember here is 21,594. That’s how many BTU-Hours 1lb of propane contains. So, if you were cooking on a grill that happened to have 21,594 BTUs, you would get 1 hour of cooking from that 1lb of propane.

That means for a 20lb propane tank you would be looking at around 20 hours of cook time.

21,594 is a very specific number and it’s unlikely that your grill actually has that exact same number of BTUs. But, all you need to do to find your burn rate is divide our magic number (21,594) by the number of BTUs your grill has.

Burn rate for a 40,000 BTU grill:21,594/40,000 = .54hrs/lb

That means you get about a half-hour of cooking time per pound of propane. If you’re cooking with 20lbs of propane, multiply your burn rate (.54) by 20 and you can expect to get about 10.8 hours of cooking time on high.

Burn rate for a 20,000 BTU grill: 21,594/20,000 = 1.08hrs/lb

Just over an hour of cooking time per pound. Or, about 21.6 hours on a 20lb propane tank (1.08×20=21.6)

Burn rate for a 200,000 BTU wok burner: 21,594/200,000 = .11hrs/lb

That’s just 2.2 hrs (.11×20=2.2) of high heat cook time from a 20lb propane tank, yikes.

So, all you need to do is look in your owner’s manual, online, or directly on your grill to find out how many BTUs you’re working with. Then, you can easily find out how long a 20lb propane tank will last for you.

Prolong The Lifespan Of Your Propane Tank

closed white propane tank

Propane itself doesn’t expire or “go bad”, so taking care of the tank itself and cooking smart will help you get the most use out of yours.

Propane tanks are safe and durable, with their one major enemy being rust. Since most tanks are painted or coated with some form of rust protection, it’s no problem to keep them outdoors and in the elements.

To get the longest life possible, you should try to keep your tank covered and out of direct sun and high levels of moisture. If you notice a lot of rust forming, it’s best to get it inspected or replaced so that it doesn’t develop a leak.

When it comes to cooking, you should always turn your propane off at the tank as well as on the grill. This will help avoid any propane loss during periods when the grill is not in use.

And while you should always preheat your grill before cooking, you should always have your mise en place ready so that you’re set to cook as soon as the grill is hot. Having your grill on while nothing is cooking, is the quickest way to waste precious propane.

Propane Usage For Common Cooking Tasks

grilling steak on a gas grill

When you calculate the burn rate for your grill, it’s generally referring to high heat cooking, or the max number of BTUs available. So grilling at a lower temp will give you more cook time.

If you’re searing steaks or cooking burgers, you’re probably cooking on high heat and burning through about 1lb of propane an hour. Luckily, high heat cooking tasks are often fairly quick. So, even though you’re burning through propane at a rapid rate you might only be cooking for 10 or 20 minutes.

On the other hand, when using medium, low, or indirect heat for things like roasting a whole chicken, or smoking a brisket you might be able to cut your burn rate in half because you’re using half the number of BTUs.

That might mean 1lb of propane could now last two hours instead of one. But, you’re also looking at much longer cooking times. 

So no matter what kind of cooking you’re doing, it’s important to think about temperature and cooking time, to estimate how much propane you’ll be using.

Final Thoughts

Smoker with Fresh Smoke Coming Out of BBQ Cooker on Outdoor Deck

While 18-20 hours of grill time is a good rule of thumb for a 20lb propane tank, a lot depends on what you’re cooking and how big your grill is. 

Just remember that high heat grilling uses more propane but usually involves shorter cook times. While medium and low heat grilling uses less propane but involves longer cook times. And it never hurts to have an extra tank at the ready.

Frequently Asked Questions

How Much Propane Does A Grill Use Per Hour?

On average, a medium-size grill will go through about a pound of propane per hour. Higher heat cooking will use more propane, while lower heat cooking will use less.

Does Propane Go Bad?

Propane does not go bad as long as it is in a properly sealed tank. 

How Much Does It Cost To Refill A 20lb Propane Tank?

An empty 20lb propane tank will generally cost somewhere between $12-$20. Propane prices can fluctuate greatly but are often between $2-$4 per gallon with a 20lb propane tank holding about 4.7 gallons. 

About the author

William is a classically trained chef, who spent years cooking in top NYC restaurants before bringing his talents home to Colorado. Now a stay-at-home dad, William has brought his passion for professional cooking home, where he continues to cook and bake for his wife and daughter.