“How much gas does a gas fireplace use?” is one of the first questions we hear once people start running their fireplace every evening. The answer is easier to figure out than most people think. Every gas fireplace has a BTU rating, and with that one number you can estimate exactly how much natural gas or propane it burns per hour.
Below, we walk through the math our team uses, give real examples, and share the habits that help you get the most comfort out of every BTU.
How Much Gas Does a Gas Fireplace Use? The Quick Answer
A gas fireplace uses gas based on its BTU input rating, which tells you how much energy it burns per hour on its highest setting.
- Natural gas: divide the BTU rating by 100,000 to get therms per hour.
- Propane: divide the BTU rating by about 91,500 to get gallons per hour.
So a fireplace rated at 30,000 BTUs per hour uses about 0.3 therms of natural gas or about 0.33 gallons of propane per hour on high.
Where to Find Your Fireplace’s BTU Rating
Look for the rating plate, usually behind the lower grille or on the inner frame of the unit. It lists the model number and the maximum BTU input per hour, often for both natural gas and propane. You’ll also find it in your owner’s manual.
For example, the Hearth & Home Technologies DV Linear Gas Fireplace we carry has a BTU input of 16,500 per hour. Larger traditional fireplaces and inserts often run higher.
The Math: Converting BTUs to Gas Use
TheU.S. Energy Information Administration lists these standard conversions:
- 1 therm of natural gas = 100,000 BTUs
- 1 cubic foot of natural gas ≈ 1,036 BTUs
- 1 gallon of propane ≈ 91,452 BTUs
Your gas bill shows usage in therms or CCF (hundred cubic feet). One CCF is roughly one therm, so the math works the same either way.
Gas Fireplace Usage by BTU Rating
Here’s how much gas a fireplace burns per hour on its highest setting, based on common BTU ratings.
|
BTU Input per Hour |
Natural Gas (Therms per Hour) |
Propane (Gallons per Hour) |
|
15,000 |
0.15 |
0.16 |
|
20,000 |
0.20 |
0.22 |
|
25,000 |
0.25 |
0.27 |
|
30,000 |
0.30 |
0.33 |
|
35,000 |
0.35 |
0.38 |
|
40,000 |
0.40 |
0.44 |
These numbers reflect full output. Most fireplaces let you turn the flame down, which lowers gas use.
How to Estimate Monthly Gas Use
Use this simple formula:
BTU rating ÷ 100,000 × hours per day × days per month = therms per month
Example: A 30,000 BTU fireplace running 3 hours a night for 30 days:
- 30,000 ÷ 100,000 = 0.3 therms per hour
- 0.3 × 3 hours = 0.9 therms per day
- 0.9 × 30 days = 27 therms per month
For propane, swap 100,000 with 91,500 to get gallons. Multiply the result by the rate on your utility bill or propane statement to estimate your own usage cost.
Putting It in Perspective: Two Common Scenarios
Numbers make more sense when you see them in real life. Here are two patterns we see often.
The evening ambiance user. You run a 25,000 BTU fireplace for about two hours most evenings, usually on a medium flame. At full output that would be 0.25 therms per hour, but running on medium brings it lower. Over a month, that adds up to well under 15 therms of natural gas for most of these households.
The zone heating user. You run a 35,000 BTU insert with a blower for six hours a day in the main living area and turn the furnace thermostat down elsewhere. At full output that’s 0.35 therms per hour, or roughly 2 therms per day. Over a month, that lands around 60 therms. In exchange, the fireplace is doing real heating work in the room you use most, which can reduce how hard your furnace works across the rest of the home.
Your own usage will depend on your settings, your home, and how often you light the fire. The formula above lets you plug in your exact numbers.
What Affects How Much Gas Your Fireplace Uses
Flame Height
Running on low uses less gas than running on high. Many remotes let you adjust flame height, and some modulate automatically.
Thermostat Mode
A remote with thermostat mode turns the fire off when the room reaches your set temperature. Your fireplace only burns gas when the room needs heat.
Hours of Use
This is the biggest factor. A fireplace you run for ambiance a few nights a week uses far less than one running all day as a primary heat source.
Pilot Type
A standing pilot burns a small flame around the clock, even when the fireplace is off. Electronic ignition systems, like the IntelliFire ignition on many Heat & Glo units, light the pilot only when you call for heat. That eliminates the gas a standing pilot uses all season. Not sure which you have? Our guide onhow to light a gas fireplace explains how to tell.
Efficiency and Venting
Sealeddirect-vent gas fireplaces deliver more of their heat into the room than older open designs. A more efficient fireplace means more warmth from every therm.
Maintenance
A clean burner and properly adjusted pilot burn more completely. Our factory-trained technicians tune both during every service visit.
Getting More Heat From Every BTU
Gas use is only half the story. What matters is how much of that heat you actually feel.
- Add a blower. A blower moves warm air into the room instead of letting it collect near the fireplace. See whether agas fireplace insert with blower is worth it.
- Use zone heating. Run the fireplace in the room you’re using and lower your main thermostat. Our guide towhether gas fireplaces heat a room explains how.
- Choose the right size. A fireplace that’s too large for the room cycles on and off or gets turned down constantly. Ourgas fireplace sizing guide helps you match output to space.
- Upgrade an old unit. Older fireplaces with standing pilots and less efficient designs may be worth replacing. Seereplacing an old gas fireplace.
Natural Gas vs. Propane Use
Propane holds slightly less energy per gallon than natural gas does per therm, so a propane fireplace uses a bit more fuel by volume for the same BTU rating. Your fireplace must be set up for the fuel you have. If your home runs on propane, ourpropane fireplace inserts guide covers your options.
A Note on Safety
Well-maintained gas appliances primarily produce carbon dioxide and water vapor as the normal byproducts of complete combustion. Carbon monoxide only forms when combustion is incomplete, such as when a burner doesn’t get enough air or the appliance malfunctions. Keep working CO alarms on every level of your home, as theU.S. Consumer Product Safety Commission recommends, and schedule an annual tune-up.Heat & Glo’s care and maintenance resources also stress regular professional service.
Want your fireplace running as efficiently as possible?Request service from Fireside and our factory-trained technicians will clean, adjust, and tune it for the season.
Frequently Asked Questions
How much gas does a gas fireplace use per hour?
Divide the BTU rating by 100,000 for therms of natural gas, or by about 91,500 for gallons of propane. A 30,000 BTU fireplace uses about 0.3 therms or 0.33 gallons per hour on high.
Does a gas fireplace pilot light use a lot of gas?
A standing pilot burns a small amount of gas around the clock. Fireplaces with electronic ignition light the pilot only when needed, which avoids that ongoing use.
Does turning the flame down save gas?
Yes. Lower flame settings burn less gas per hour than running on high.
Does a propane fireplace use more fuel than natural gas?
By volume, slightly. Propane contains about 91,452 BTUs per gallon, so a propane fireplace uses a bit more than one gallon for every 100,000 BTUs.
Where do I find my fireplace’s BTU rating?
Check the rating plate behind the lower grille or on the inner frame, or look in your owner’s manual.