EN/US · unofficial estimator
How much does a gas fireplace cost to run?
GasFireCost turns fireplace BTU/hr, hours of use, and your $/therm or $/gallon into live hourly, daily, monthly, and seasonal cost. Fuel math only — no OEM or utility affiliation.
Running cost calculator
US default $1.47/therm. Using default.
Default 720 hours (hours/day × 180 days).
Per hour
$0.59
Main burner
Per day
$2.35
4 h on
Per month
$70.56
Per season
$423.36
720 h
Fuel use: 0.4 therms/hour of burner time (40,000 BTU/hr after assumptions).
GasFireCost is unofficial. It estimates fuel cost from BTU ratings and the rates you enter. It does not include taxes, utility customer charges, tank rental, or installation. No affiliation with OEMs or utilities. Verify rates with your utility or propane supplier. See methodology.
- Month
- $70.56
- Season
- $423.36
How to estimate running cost
- Choose natural gas or propane.
- Enter fireplace BTU/hr (or tap a 20k–50k preset).
- Set hours per day, days per month, and season hours.
- Keep the US default rate or tap Edit rate to match your bill.
- Read per-hour through per-season totals and copy a share link.
What the numbers mean
Natural gas is billed in therms (100,000 BTU). Propane is billed in gallons (91,500 BTU in this calculator). Cost per hour is fuel burned by the main burner times your rate. Month and season scale that by the hours you enter. A standing pilot is optional extra fuel.
The 75% efficiency toggle is an assumption for vented units: if you treat the BTU figure as heat to the room, fuel input is BTU ÷ efficiency. If your rating is already fuel input, turn the derate off.
Typical running cost by BTU (US defaults)
Same formula as the calculator: fuel units × rate ÷ efficiency. Defaults: 75% efficiency, $1.47/therm natural gas, $2.67/gallon propane, 4 hours/day × 30 days for monthly. Full side-by-side: Natural gas vs propane fireplace.
| BTU/hr | $/hour | $/month (4 h × 30) |
|---|---|---|
| 20,000 | $0.39 | $47.04 |
| 30,000 | $0.59 | $70.56 |
| 40,000 | $0.78 | $94.08 |
| 50,000 | $0.98 | $117.60 |
| BTU/hr | $/hour | $/month (4 h × 30) |
|---|---|---|
| 20,000 | $0.78 | $93.38 |
| 30,000 | $1.17 | $140.07 |
| 40,000 | $1.56 | $186.76 |
| 50,000 | $1.95 | $233.45 |
Frequently asked questions
How much does a gas fireplace cost per hour?
With the site’s US defaults (30,000 BTU/hr, 75% efficiency assumption, $1.47/therm), a natural gas fireplace is about $0.59 per hour. The same unit on propane at $2.67/gallon is about $1.17 per hour. Your bill depends on nameplate BTU, local rates, and hours used.
What does a gas fireplace cost per month?
At 4 hours per day for 30 days, the default natural gas example is about $71 per month, or about $140 on propane. Cut hours in half and the main-burner cost halves. A 24-hour pilot adds a smaller, steadier monthly amount.
How much does a standing pilot light cost?
A 600–1,000 BTU/hr pilot running 24 hours uses about 0.14–0.24 therms per day on natural gas, or roughly $6–$11 per month at $1.47/therm before the main burner. Enable “pilot light on” in the calculator and set BTU/hr from your manual.
Is GasFireCost affiliated with a utility or fireplace brand?
No. GasFireCost is an unofficial estimator. It is not a utility, OEM, dealer, or billing tool. Figures are planning estimates. Confirm rates, therm factors, and appliance ratings with your utility, propane supplier, and the fireplace manual.
Is a therm the same as a CCF on my gas bill?
Not always. A therm is 100,000 BTU. A CCF is 100 cubic feet of gas, which is close to one therm but the exact heat content varies by utility. If your bill is in CCF or MCF, convert using the therm factor printed on the bill, then enter $/therm in the calculator.
How many BTU are in a gallon of propane?
This calculator uses 91,500 BTU per gallon as a round US planning number. The US Energy Information Administration’s HD-5 propane conversion is 91,452 BTU per gallon (higher heating value). The difference is under 0.1% and does not change a household estimate in a meaningful way.
Why is efficiency set to 75% by default?
Many vented gas fireplaces deliver roughly 70–80% of nameplate heat to the room; the rest leaves with exhaust. The derate is an assumption, not a lab rating. If your BTU/hr is already the input (fuel) rating, turn the derate off so cost tracks fuel burned, not heat delivered.
Is natural gas cheaper than propane for a fireplace?
Usually, on a per-BTU basis, yes — at these US defaults natural gas is about half the hourly cost of propane for the same fireplace. Propane can still be the practical fuel where there is no gas main. Compare with your actual $/therm and $/gallon, not national averages.
What are “season hours”?
Season hours are the total hours you expect the main burner on across a heating season. The default is 4 hours/day × 180 days = 720 hours. Edit that field if you only use the fireplace on weekends or for a shorter winter.
How does GasFireCost estimate fireplace running cost?
It converts your fireplace BTU/hr into therms (natural gas) or gallons (propane), multiplies by the fuel rate you enter, then scales by hours per day, days per month, and seasonal hours. An optional efficiency derate treats the BTU figure as heat output. A standing pilot, if enabled, is extra fuel on top of the main burner.