How long will a 100 lb propane tank run a gas fireplace?
A full 100 lb cylinder holds about 23 gallons — roughly 2.1 million BTU — so a fireplace burning 30,000 BTU an hour runs about 70 hours wide open. In real terms, that's two to four weeks of typical evening use, but only a matter of days if the fireplace is your main heat running around the clock.
Doing the numbers
A 100-pound propane cylinder filled to the safe 80% carries around 23 gallons, and propane gives about 91,000 BTU per gallon — call it 2.1 million BTU in the tank. Divide by your fireplace's burn rate: a 30,000-BTU unit on high uses that much in roughly 70 hours of actual flame time. Almost no one runs a fireplace continuously, though. A few hours most evenings through a WNC winter, and one 100 lb cylinder commonly lasts a few weeks to a month. Lean on it hard during a cold snap and it empties much faster.
Where a 100-pounder hits its limit
Two 100 lb cylinders are a common setup for a single fireplace at a cabin, but they have a ceiling. In deep cold, one small cylinder may not vaporize fast enough to feed a hungry fireplace — the same frost-and-fade you see on a grill tank, scaled up. That's why suppliers often manifold two cylinders together or step you up to a stationary 120- or 250-gallon tank if the fireplace runs a lot. If you find yourself swapping cylinders constantly, that's the signal to size up.
Sizing it for how you actually live
The honest answer to how long depends entirely on your BTU rate and your habits, and we'd rather size the fuel supply to your real use than guess. During an assessment we look at the fireplace you're running, how hard you lean on it — ambiance most nights, or backup heat when the power's out after a storm — and coordinate tank capacity with your propane supplier while we handle the licensed line. Call (828) 545-0525.
How we can help
Related questions
- What size propane tank do I need to run a gas fireplace?
- How long will a 500-gallon propane tank last if I use my fireplace regularly?
- Do I need a bigger propane tank if I add a gas fireplace?
- How much does it cost per hour to run a propane fireplace?
- Can propane freeze or stop flowing in very cold weather?
- How do I know if my house has natural gas or propane?
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