How much does it cost to run a gas fireplace per hour?
Take the fireplace's BTU input, divide by 100,000, and you have therms of natural gas burned per hour at full flame — multiply by the per-therm rate on your bill and that's your number. Our best-selling Napoleon Ascent 36, at 26,500 BTU, burns just over a quarter of a therm an hour wide open; on propane, figure roughly a gallon per 91,500 BTU.
The counter math we do for customers
Every gas fireplace has an input rating on its plate and in its manual — that's gas consumed, not heat delivered. Natural gas is billed in therms, and a therm is 100,000 BTU, so a 40,000 BTU unit like the Heat & Glo 6000CLX burns four-tenths of a therm each hour at maximum. Propane holds about 91,500 BTU per gallon, so a 30,000 BTU unit like the Kozy Heat Springfield 36 — the one we spec for propane-country cabins — draws about a third of a gallon per hour flat out. Your utility or propane rate does the rest; we can't quote that number for you, but your bill can.
Why your real cost runs under the nameplate
Almost nobody runs a fireplace pinned at maximum all evening. Modern burners modulate — the Valor H5 tops out at 24,000 BTU but turns down to 9,000, roughly a third of the fuel for a fire that's still very much alive — and thermostatic units cycle themselves down as the room warms. Figure your realistic cost from a mid-range flame, not the max, and the per-hour numbers get pleasantly smaller.
The WNC fuel wrinkle
On the natural-gas mains through Asheville, Hendersonville, Fletcher, and Arden, per-hour cost for a sealed unit is genuinely modest. Out in propane country — Fairview, Candler, Brevard, and the cabins — propane costs more per BTU, so full-flame hours bite harder; that's exactly where modulating, high-efficiency units earn their keep. Either way, an hour of fireplace beats an hour of heating the whole house when you only need one warm room. More on the fuels in our [natural gas vs. propane guide](/guides/natural-gas-vs-propane-in-wnc), or call (828) 545-0525.
Related questions
- How much will a gas fireplace add to my monthly gas bill?
- How do I calculate what my gas fireplace costs to run from its BTU rating?
- How much propane does a gas fireplace use per hour?
- Is it cheaper to run my gas fireplace or my furnace?
- What's the cheapest type of fireplace to run?
- How much does a gas fireplace cost installed?
Still deciding? Talk to a real installer.
Free assessments across Western North Carolina — no pressure, straight answers.