Fireplace running cost FAQ

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.

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.

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.

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.

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.

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.

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.

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.

GasFireCost only does gas and propane fuel math. An electric unit is billed in kWh. Roughly, 1 kWh is 3,412 BTU, so a 5,000 BTU electric heater uses about 1.5 kWh per hour. Multiply by your electric rate for a separate estimate; this site does not mix the two fuels.

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.

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.

Yes. Use Copy share link on the calculator. The URL stores fuel, BTU, hours, days, rate, pilot, efficiency, and season hours as query parameters so someone else can open the same scenario.