Gas Fireplace Efficiency

Gas Fireplace Efficiency Explained (With Real Examples)

In Gas Fireplaces by James O'KellyLeave a Comment

Gas fireplaces use gas as the source of fuel in order to produce heat for a home and ‘efficiency’ refers to the ability for a fireplace appliance such as gas to convert that fuel into usable heat.

With a few different types of gas fireplace available there can be a wide range in their efficiencies, and so are gas fireplaces efficient overall?

Natural vent gas fireplaces in the form of inserts can typically be found to have efficiency ratings of around 50-60%, while gas logs sets may be lower than this. Direct vent gas fireplaces can typically average between 60-80% efficiency and ventless gas fireplaces can be around 99% efficient.

Our own gas fireplace is a natural vent insert model, which we discuss in more detail below including what the official efficiency rating of our gas insert is.

Are Gas Fireplaces Efficient?

The efficiency rating that you can expect from a gas fireplace often comes down to what type of gas fireplace it is.

  • Ventless gas fireplaces are typically the most efficient from of gas fireplace. Ventless gas fireplaces don’t have any form of external ventilation and so the fuel must be burnt cleanly enough in order to be able to safely put waste air back into the room. As a result, ventless gas fireplaces can be found to be almost 100% efficient and the efficiency rating may not be found stated anywhere on a ventless gas fireplace because they’re designed to be so efficient.
Ventless Gas Fireplace
For safety purposes, ventless gas fireplaces can be the most efficient form of gas fireplace
  • Direct vent gas fireplaces are typically the second most efficient form of gas fireplace. Direct vent models vent both clean and waste air externally and are able to produce heat for a home from burning gas very efficiently. Expect to find direct vent gas fireplaces with efficiency ratings of 70% on average but can be as high as 80% or low as 60% depending on the model.
Direct Vent Gas Fireplace
Modern direct vent gas fireplaces can be very efficient
  • Natural vent gas fireplace inserts vent waste air externally but take fresh air from inside the home. As a result, natural vent gas fireplace inserts can lose more heat up the chimney compared to direct vent gas fireplaces and be less efficient as a result. Expect a natural vent gas fireplace insert to have around 50%-60% efficiency but again this can vary depending on the make and model, and its age.
Gas Fireplace Real Flames
Natural vent gas fireplaces aren’t as efficient as other types
  • Gas fireplace logs are installed inside masonry open fireplaces much like natural vent gas fireplace inserts but can be found to be least efficient form of gas fireplace because much of the heat can be lost up the chimney. Gas logs will still be more efficient than the wood burning fireplace that that they sit inside, however.
Clean Gas Fireplace
Gas logs can be the least efficient form of gas fireplace

Other factors can influence how efficient a gas fireplace is, including the make and model.

Gas Fireplace Efficiency Example

Our own gas fireplace is a natural vent insert version. It was already installed in the masonry fireplace in the living room when the house was bought.

Gas Fireplace Insert
Our own gas fireplace is the natural vent type and so isn’t the most efficient form of gas fireplace you can buy

As this is a natural vent gas fireplace, we can’t expect it to be quite as efficient as other direct vent or ventless gas fireplaces but can expect it to be more efficient than gas logs, and far more efficient than the wood burning fireplace it replaced.

For new gas fireplaces, the efficiency rating of a particular gas fireplace may be displayed on the product page of the website or on the box.

For gas fireplaces already installed it may be possible to find the efficiency rating on the fireplace itself. Gas fireplaces are typically found with a rating plate found somewhere on the unit that details information about that specific fireplace.

For example, the rating plate for our gas fireplace can be found to the left of the controls inside the burner assembly at the base of the unit.

Gas Fireplace Burner Assembly
Identifying the location of the rating plate may tell you the efficiency rating of that gas fireplace, or point you in the direction of where you can find out
Gas Fireplace Data Plate
The rating/data plate for our own gas fireplace is located in the same compartment as the controls

The rating plate may display the efficiency rating, but if not it can probably be found within the owner’s manual.

If you don’t have the manual then you can use the information displayed on the rating plate to find an electronic copy of the right manual for your gas fireplace.

The efficiency rating of our gas fireplace isn’t shown on the rating plate but can be found in the manual.

The efficiency rating for our particular gas fireplace insert is as follows:

  • Useful energy efficiency at nominal heat output: 57.9%
  • Useful energy efficiency at minimum load: 57.9%

The efficiency of our gas fireplace falls within the average 50%-60% range expected for natural vent gas fireplaces.

However, this gas fireplace is fairly old and when we eventually replace it we expect the newer model to be more efficient.

Gas Fireplace Efficiency vs Other Types Of Fireplace

When compared with other forms of fireplace and stove, gas fireplaces on a whole can be considered to be very efficient forms of fireplace.

We have a range of fireplaces and stoves in the family, including:

  • Traditional open wood burning fireplaces
  • Gas fireplace
  • Pellet stove
  • Wood burning stove
  • Multi fuel stove
  • Electric fireplace
Pellet Stove & Wood Stove
Our pellet stove and wood burning stove, both of which can be as less or more efficient than a gas fireplace depending on which type of gas fireplace you’re comparing

Comparing our gas fireplace to our other fireplaces and stoves in terms of stated ‘efficiency’ ratings:

Gas Fireplace57.9%
Pellet Stove87.8%
Wood Burning Stove71.6%
Multi Fuel Stove78.9%
Open FireplaceTypically around 10%
Electric Fireplace100%
The efficiency ratings of our own range of fireplaces and stoves

Although our gas fireplace is lower in terms of efficiency it should be noted that we do own a natural vent gas fireplace insert, which are typically less efficient compared to the other main types of gas fireplace including direct vent and ventless.

A direct vent gas fireplace would typically have an efficiency of around 70%, which would be similar to our forms of wood burning stove.

A ventless gas fireplace can provide a similar efficiency rating as an electric fireplace of up to 100%.

Gas Fireplace Pilot Light Efficiency

More modern gas fireplaces are often much more efficient compared to older models as a result of the use of intermittent pilot ignition systems rather than the conventional standing pilot ignitions.

With intermittent pilot ignitions, the pilot is turned on and off as required.

With the more conventional standing pilot ignition system, the pilot flame stays on between fires.

Gas Fireplace Ignition
A gas fireplace that uses a standing pilot light (like ours) can be less efficient than those that use intermittent pilot ignition systems

Our gas fireplace uses the older standing pilot ignition and we leave this pilot flame on throughout winter.

Using a gas fireplace with such an ignition system can lead to wastage of gas over time (albeit small amounts but can add up over time), thus making these types of gas fireplaces less efficient than those that use an intermitted pilot ignition where the pilot starts and cuts off on demand.

We’ve discussed standing and intermittent pilot flames in more detail in another article.

Further Reading

Are Gas Fireplaces Worth It?

Do Gas Fireplaces Use A Lot Of Gas?

How To Know If You Have A Gas Fireplace

What’s Inside A Gas Fireplace

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