If you're getting ready for a chilly night on the patio, you probably need to know how long does propane tank last in outdoor heater units before the flame flickers out and everyone heads back inside. There is nothing quite as mood-killing as a patio heater dying right in the middle of a good conversation or a backyard dinner party.
The short answer is that for most standard full-sized patio heaters using a 20-pound tank, you're looking at anywhere from 8 to 12 hours of burn time. But honestly, that's a bit of a range, and a lot depends on how you're using the thing. Let's break down why that number fluctuates and how you can avoid being the person who runs out of gas at the worst possible moment.
The standard 20-pound tank timeline
Most people use the classic 20-pound propane tank—the same kind you'd hook up to a backyard grill. When you fill one of these up at a swap station, it's usually holding about 4.7 gallons of liquid propane.
If you've got a typical freestanding patio heater, it probably puts out around 40,000 to 45,000 BTUs (British Thermal Units) per hour when it's cranked up to the highest setting. Since a gallon of propane holds about 91,500 BTUs, you're basically burning through a gallon every two hours or so. Do the math, and that brings you to that 9-to-10-hour mark.
Now, if you're using a smaller tabletop heater, those are usually way less powerful—maybe around 10,000 BTUs. In that case, that same tank could last you 30 or 40 hours. But for the big ones that keep the whole deck warm, 10 hours is the gold standard you should plan for.
Why the BTU rating changes everything
You'll see the "BTU" number plastered all over the box when you buy a heater. Think of BTUs like the horsepower of your heater. The higher the number, the more heat it pumps out, but the more fuel it chugs to do it.
Most full-sized commercial-style heaters sit in that 40,000 to 48,000 BTU range. If you bought a heavy-duty model because you live somewhere like Chicago or Maine, it might even go higher. If you leave that thing on "High" the entire night, you're going to hit the lower end of the lifespan—maybe only 8 hours.
However, most of us don't actually need it on full blast once the area is warmed up. If you turn the dial down to "Medium" or "Low," you can easily stretch that tank to 15 hours or more. It's all about finding that sweet spot where you aren't shivering but you aren't melting your eyebrows off either.
Environmental factors you can't ignore
It isn't just about the machine itself; the world around you plays a huge part in how long that gas lasts.
The Outside Temperature Propane is stored as a liquid under pressure. When it gets really, really cold outside—we're talking well below freezing—the pressure inside the tank drops. This can actually make the heater less efficient, and you might find yourself turning the dial higher just to get the same amount of warmth you'd get on a mild autumn evening.
The Wind Factor Wind is the enemy of the outdoor heater. If it's breezy, that heat is getting blown away before it ever reaches you. You'll instinctively turn the heater up to compensate, which drains the tank faster. Plus, if it's windy enough to blow out the pilot light, you're losing gas every time you have to relight it. If you can, tuck your heater into a corner or behind a windbreak to keep that heat focused where it belongs.
Ways to stretch your propane further
If you don't feel like running to the gas station every other weekend, there are a few tricks to make that tank last a bit longer.
- Warm up the space first: Start the heater on high for about 10 or 15 minutes to get the immediate area warm, then dial it back to the lowest comfortable setting.
- Check the seals: Use some soapy water on the connection point between the tank and the regulator. If you see bubbles, you've got a leak. Even a tiny leak can waste a surprising amount of gas over a few days.
- Use reflectors: Some heaters have adjustable hoods or reflectors. By directing the heat toward your seating area rather than letting it escape into the sky, you can stay warmer on a lower setting.
- Positioning is key: Don't put the heater in the middle of a wide-open yard if you don't have to. Placing it near a wall (at a safe distance, of course) helps trap some of that ambient heat.
How to tell when you're running on empty
There's nothing worse than the "did it just get colder?" realization. Since most propane tanks are solid metal, you can't exactly see through them to check the level.
One of the easiest ways to check is the warm water trick. Take a cup of hot (not boiling) tap water and pour it down the side of the tank. Then, run your hand down the metal. The part of the tank that has liquid propane inside will feel cold to the touch, while the empty part at the top will feel warm from the water. Where it switches from warm to cold is your fuel line.
You could also buy a pressure gauge that screws in between the tank and the heater. These aren't 100% perfect because they change based on the outside temperature, but they give you a much better "red zone" warning than just guessing.
Lastly, there's the weight. A standard 20lb tank weighs about 17 pounds when it's empty (this is called the "tare weight," usually stamped on the handle). When it's full, it weighs around 37 pounds. If you can pick it up with one finger, you're probably about to have a very cold night.
The bottom line on tank life
So, how long does propane tank last in outdoor heater setups? If you're planning a party that's going to go late into the night, just assume you'll get about one full evening out of a single tank if you're running it at a decent clip.
If you use your heater for just an hour or two every night while you have your evening coffee, you can probably go a week or two without a refill. The best move is to always keep a spare tank in the garage. Propane doesn't "go bad," so having a backup is the only real way to ensure you aren't left in the cold when the conversation is just getting good.
Just remember to turn the valve off completely when you're done. It sounds obvious, but a slightly open valve is the number one reason people find themselves with a "mystery" empty tank the next time they go to use it. Stay warm!