Ventless Gas Fireplace

How Much Gas Does A Gas Fireplace Use?

In Gas Fireplaces by James O'Kelly2 Comments

Gas fireplace technology has progressed over recent years allowing gas fireplaces to run more efficiently and use less gas compared to older models.

How much gas a gas fireplace uses can depend on the type of gas fireplace, the age of the fireplace, how often it’s used and what heat setting it’s on, but do gas fireplaces use a lot of gas in general?

An average 40,000BTU gas fireplace burning natural gas will typically use 1 therm of gas, equivalent to 100 cubic feet of gas, every 2 and a half hours. A 40,000 BTU gas fireplace burning propane will typically go through 1 gallon of propane in just over 2 hours.

How much gas a gas fireplace uses will be down to a range of factors and so we’ve explained in more detail below using our own gas fireplace as an example:

  • What types of fuel gas fireplaces use and how much is used per hour.
  • What other factors can affect how much gas a gas fireplace uses.

How Much Gas Does A Gas Fireplace Use?

The amount of heat a gas fireplace produces can vary between around 10,000BTUs to 70,000BTUs, but can be more or less than this depending on the type and model of gas fireplace. You can expect a standard gas fireplace to be around 30-40,000BTUs.

A gas fireplace heat output might be shortened, to 30kBTU for 30,000BTU for example, for simplicity purposes.

BTU is a standard measurement of heat, and is short for British Thermal Unit. A 40,000BTU gas fireplace will therefore consume 40,000BTUs worth of gas every hour.

Depending on where you live, gas fireplaces may be rated in kW rather than BTUs.

There are typically two fuel options when it comes to using gas fireplaces, and each have their own fuel usage conversions for when working out how much gas a gas fireplace uses.

  • Natural Gas
  • Propane

100 cubic feet of natural gas is equivalent to 100,000BTUs, or 1 Therm.

1 gallon of liquid propane is equivalent to 91,500 BTUs.

We have a gas fireplace insert installed within a living room fireplace. It’s a traditional natural vent gas fireplace and is connected up to the house gas main and therefore uses natural gas as the fuel.

Gas Fireplace
Our gas fireplace, and the one we use as an example throughout this article

As this is a relatively old model of gas fireplace it utilizes a standing pilot light.

This means that the gas fireplace burns a small amount of fuel constantly so that it’s always on, and the flames and heat can be brought to full strength immediately.

A standing pilot light can be common among older models of gas fireplace that don’t have an electrical connection. For example, our gas fireplace isn’t connected up to the mains electrics and so must generate its own spark to start the flames.

However, newer models of gas fireplace may use an Intermittent Pilot Ignition (IPI) system where the fireplace is connected to the house electricity supply, using a standard electrical outlet plug for example, and the pilot can be started as an when required.

This means that more modern gas fireplaces may not be using gas at a constant rate and can use less gas overall compared to older versions of gas fireplaces.

Gas fireplace efficiency can also play a role in how much gas a gas fireplace uses. More efficient gas fireplaces that convert gas to useable heat better may not need to be run at higher heat settings and therefore use less gas compared to less efficient gas fireplaces.

Factors that can influence how much gas a gas fireplace uses can include:

  • The type of fireplace (natural vent, direct vent or ventless)
  • Fuel type (natural gas or propane)
  • Standing pilot or intermittent pilot light
  • Efficiency of the fireplace
  • Maximum heat output available.

Natural Gas Fireplace Gas Usage Example

To help explain how much gas a gas fireplace uses we’ll use our own gas fireplace as an example.

The specifications for our own particular gas fireplace are as follows:

  • 6.2kW max energy input
  • 3.5kW max energy input
  • Pilot rate 210W

The units for working out how much gas a gas fireplace uses are:

The rate of use of natural gas is typically provided in Therms.

1 Therm is equal to 100,000BTUs.

1 Therm is also equivalent to 100 cubic feet of natural gas.

The maximum energy input for our natural gas fireplace is 6.2kW, which is equivalent to 21,150BTUs/hour. The minimum energy input of 3.5kW is equal to approximately 11,950BTUs.

Therefore, if we were to run our gas fireplace on maximum heat setting it would be using approximately 21 cubic feet of natural gas per hour.

It would therefore take approximately just under 5 hours for our particular model of gas fireplace to use 1 Therm of energy, or use 100,000 BTUs worth.

If you know the average gas rate cost for your local area then you can work out how much it typically costs to run as gas fireplace.

Our gas fireplace is an older model and may produce less heat and use less gas compared to the average modern gas fireplace. Expect an average gas fireplace to use more gas than ours.

How Much Gas Does A Gas Fireplace Pilot Light Use?

A typical standing pilot light on a gas fireplace with an energy usage of 210W or 715BTUs will consume approximately 0.715 cubic feet of gas per hour, or 17 cubic feet of gas per day.

If a gas fireplace uses a traditional standing pilot light then you’ll need to take into account that it will be on continuously until you turn the gas fireplace off completely.

A gas fireplace pilot light will use far less gas compared to the normal burner on a gas fireplace, but as gas fireplace pilot lights stay on continuously this usage can add up.

For example, our own particular model of gas fireplace has a pilot light, which has a 210W energy usage, equivalent to around 715BTUs.

Our gas fireplace would use approximately .17 Therm of energy per day if the pilot light was left running continuously without the gas fireplace being used for heating purposes.

Gas Fireplace Pilot Light
Our gas fireplace uses a traditional standing pilot, where small amounts of gas are used consistently but this can add up to large amount over time

Not all gas fireplaces will have standing pilot light and many new gas fireplaces use an intermittent pilot light that only turns on when required. These gas fireplaces will typically require electricity in order to achieve this but can be more efficient than gas fireplaces with standing pilot lights, which are often seen as wasteful.

Do Gas Fireplaces Use A Lot Of Gas?

Modern gas fireplace units with intermittent pilot ignition systems, improved energy usage and increased efficiency at being able to transfer heat to a room will typically use less gas compared to an older model of gas fireplace with the equivalent energy input rating.

Standing pilot lights, commonly found on older models of gas fireplace, won’t use much energy per hour compared to a gas fireplace on full heat setting, but the amount of gas used can add up over time.

Gas Fireplace Controls
More modern gas fireplaces (compared to ours) may use an intermittent pilot light rather than a standing one, which can save gas in the long run

However, many modern gas fireplaces use intermittent pilot lighting to help keep wastage of fuel to a minimum.

An average 40,000BTU gas fireplace on full heat will use approximately 10 Therms of energy per day.

Depending on the age of a gas fireplace and its maximum heat output, a gas fireplace can use a relatively large amounts of gas if used at max settings for a number of hours per day.

However, gas fireplaces be a very cost-effective form of heating, especially if using natural gas rather than propane.

Further Reading

Are Gas Fireplaces Worth Buying?

Do Gas Fireplaces Need To Be Vented?


  1. extremely detailed explanation, very useful as we are about to buy a new gas fireplace. thank you.

  2. Thank you so much for the time you put into this informative article. I am trying to save money this year with my gas bill and have a question that seems like a no brainer but I’m new to my gas fireplace and need some advice. Last year I ran my gas fireplace with the flame as low as I could and assumed it would made a difference in the amount of gas it used. It seems logical but this year it is so cold I wondered if turning the flame up would increase my gas consumption. I have an older gas fireplace that still works great for me but was wondering about the flame. Also thank you for the info on the pilot light. I left mine on all through the summer because I wasn’t confident on how to restart the light. Thanks for your help.

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