How long will a 20 lb propane tank last in a patio heater?
Nothing kills a patio night faster than a heater sputtering out at 9 p.m. If you've ever stood there shaking a tank to guess how much is left, you already know the guessing game isn't great odds. A 20 lb propane tank holds a fixed amount of energy no matter what it's hooked up to, so how long it lasts really comes down to one number: the BTU rating of your heater, and where you've got the dial set.
How Long Does a 20 lb Propane Tank Last With Different Types of Heaters?
Patio heaters aren't all built the same, and BTU output varies a lot between styles. Here's roughly what to expect from a full 20 lb tank, run continuously on the highest setting:
| Heater Type | Typical BTU Range | Runtime on High |
|---|---|---|
| Compact tabletop / mushroom heater | ~40,000 BTU | ~10.5–11 hours |
| Rolling patio heater (base-mount) | ~41,000 BTU | ~10 hours |
| Pyramid / glass tube heater | ~48,000 BTU | ~9 hours |
| Standing table-top patio heater | ~50,000 BTU | ~8.5 hours |
| Propane fire pit / fire bowl | ~60,000 BTU | ~7 hours |
These are worst-case numbers, meant for a heater cranked to max the entire time. In practice, most people run heaters on medium once the space warms up, which stretches things out considerably.
How Do You Calculate How Long a Propane Tank Will Last?
You don't need a chart to figure this out for your own setup. It's one formula, and it works for any heater once you know its BTU rating.
A standard 20 lb propane tank holds about 4.7 gallons of liquid propane. Propane carries roughly 91,500 BTU of usable energy per gallon, so:
4.7 gallons × 91,500 BTU/gallon ≈ 430,000 BTU per full tank
430,000 BTU ÷ 50,000 BTU per hour = 8.6 hours of continuous high heat from one full tank.
Drop it to a medium setting (roughly 30,000 BTU of actual draw) and that same tank stretches to around 14 hours.
One caveat worth knowing: most tanks aren't filled to a literal 20 lbs by weight — propane suppliers typically fill to about 80% capacity to leave room for the gas to expand in warm weather. So real-world runtime often lands a little under the theoretical max, which is exactly why the numbers above are meant as a solid estimate, not a guarantee down to the minute.
What Factors Affect Propane Tank Runtime?
Heater BTU Output
This is the single biggest lever. A 60,000 BTU fire pit burns through fuel roughly 50% faster than a 40,000 BTU tabletop unit, simply because it's pulling more gas per hour to produce more heat. If you're mainly heating a small balcony or a two-person seating nook, a lower-BTU unit like the 41,000 BTU Pyra Base heater stretches your tank noticeably further than something built for a large open patio.
Heat Setting
Most patio heaters don't burn at their rated BTU unless the dial is turned all the way up. Running on low or medium can cut fuel draw by 40–60%. If you're just taking the chill off rather than trying to sit outside in near-freezing temps, keeping the heater on medium is the easiest way to double your tank life without doing anything else.
Weather Conditions
Cold ambient temperatures slow how efficiently liquid propane vaporizes inside the tank, which can make a heater struggle to hit full output, especially once the tank drops below roughly a quarter full in freezing weather. Wind is the bigger practical issue, though: it strips heat away before it reaches anyone, so people tend to crank the dial higher to compensate, which burns fuel faster even though the BTU rating hasn't changed. A heater with a wider heat-reflector design, or one paired with some kind of windbreak, holds its warmth better in gusty conditions and needs less brute-force output to feel the same.
How Much Propane Does a Patio Heater Use Per Hour?
Flip the formula around and you get gallons burned per hour, which is handy if you're trying to figure out how many tanks to keep on hand for a long event.
| Heater BTU | Approx. Fuel Use | Approx. Cost per Hour* |
|---|---|---|
| 40,000 BTU | ~0.44 gal/hr | Low |
| 41,000 BTU | ~0.45 gal/hr | Low |
| 48,000 BTU | ~0.52 gal/hr | Moderate |
| 50,000 BTU | ~0.55 gal/hr | Moderate |
| 60,000 BTU | ~0.66 gal/hr | Higher |
*Propane prices vary by region and season, so exact per-hour cost will depend on local refill or exchange pricing.
How Can You Make Your Propane Tank Last Longer?
Run it on medium once the air warms up
Most people crank the heater to high just to get the initial chill off, then forget to dial it back. That first-five-minutes habit is where a lot of wasted propane goes.
Block the wind instead of fighting it
A heater working against a steady breeze burns fuel to fight losses it'll never win. Positioning against a wall, screen, or planter cuts down on how hard the burner has to work.
Match the heater size to the space
A 60,000 BTU fire pit is overkill for a small balcony, and running it on low the whole night to compensate is less efficient than starting with a right-sized 41,000 BTU unit like the Pyra Base Patio Heater in the first place.
Check connections for leaks
A soapy-water test on the hose and regulator (bubbles mean a leak) takes two minutes and can catch fuel loss you'd otherwise never notice.
Keep a backup tank on hand for long events
If you're hosting past the 8-hour mark on a 50,000 BTU unit, having a second tank ready means you're not scrambling mid-party. Some hosts running a bigger space find it easier to size up to a lower-draw model like the 41,000 BTU option for the same footprint instead of running a higher-output heater on low all night.
Store tanks upright and out of direct sun
When not in use, heat buildup affects tank pressure and, over time, the gauge accuracy if your tank has one.
FAQ
How long does a 20 lb propane tank last on a 50,000 BTU patio heater?
Roughly 8 to 9 hours on the highest setting. Since most 50,000 BTU heaters — including Pamapic's Pyra Mesa Patio Heater — reach comfortable warmth well before full output, keeping it on medium for most of the evening can push that closer to 13–14 hours from the same tank.
How long does a propane tank last on a patio heater?
It depends entirely on the heater's BTU rating and how high you're running it, but for most residential patio heaters (40,000–60,000 BTU), expect somewhere between 7 and 11 hours of continuous use on high, and noticeably longer on lower settings.
Can I leave a propane patio heater running overnight?
Manufacturer instructions for patio heaters, including CSA-certified units, consistently call for turning the heater off whenever it's unattended. Leaving any open-flame gas appliance running overnight unsupervised carries fire and carbon monoxide risks, and most safety features like tip-over shutoff aren't designed to replace someone keeping an eye on it. It's best to shut it off before heading to bed, even if the tank still has fuel left.
How do I know when my propane tank is empty?
The most reliable method doesn't need a gauge: pour warm water down the side of the tank, then run your hand down the same spot. The section still holding liquid propane will feel noticeably cooler than the empty section above it — that temperature line marks the fuel level. You can also weigh the tank; an empty 20 lb tank typically weighs around 17 lbs (its tare weight, usually stamped on the collar), and a full one weighs close to 37 lbs.
Conclusion
A 20 lb tank typically gives you 7 to 11 hours of warmth, depending on your heater's BTU output and heat setting. Lower output and a gentler setting stretch that even further.
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