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Can a Gas Fireplace Heat a Room?

Gas fireplaces can heat a room. With a heat output ranging from 8,000 to 60,000 BTUs, a gas fireplace can be the right solution for a variety of heating needs.

However, there’s more to the story than just that. Depending on the circumstances, a gas fireplace may not be the best solution for heating a room. And even if you do choose a gas fireplace for your heating needs, there are certain drawbacks you’ll want to know. Let’s dive in a little more deeply.

Do Gas Fireplaces Heat Up a Room?

Although gas fireplaces do warm up the room they’re in to some degree, they often need a furnace’s help to make the room fully comfortable for an extended period of time. So for heating up a room, a gas fireplace is not as effective as a primary heat source, such as central heat.

It does make a great, warm, cozy supplementary heat source, though. Let’s take a look at the full capabilities of a gas fireplace. How does it compare to other heat sources? Where might it fit into your heating strategy?

What’s the Heat Output from Gas Fireplaces?

The heat output of gas fireplaces is between 8,000 and 60,000 BTUs, depending on the model—as much as 8,000 to 60,000 matches. 

Heat output is measured in British Thermal Units, or “BTUs”. One BTU equals the amount of heat you need to raise the temperature of one pound of water up one degree Fahrenheit. This is roughly as much heat as one lit match produces. 

In contrast, a gas central heating system can produce substantially more—about 40,000 to 140,000 BTUs per hour. An oil furnace is similar, giving off between 60,000 and 160,000 BTUs. Even a less-potent electric furnace can produce 34,000 to 85,000 BTUs. And most boilers produce 75,000 to 180,000 BTUs per hour.

The thing is, though, more BTUs are not always better. It’s important to match the BTUs of your heater to the size of your heated space. While you might think that extra BTUs would be helpful—if you double the BTUs of your heater, your room would heat twice as fast, right?—but actually, you will just over-heat your room.

So the extra BTUs of a central heating system doesn’t necessarily mean that central heating is better for your specific needs.

It takes about 20 BTUs to heat about one square foot. You can use this figure to calculate how many BTUs your heater will need to produce in order to heat your space.

For example, a 40,000 BTU gas fireplace would be perfect for a 2,000 square foot space. A 40,000 BTU central heating system would perform just as well. However, in a 1,000 square foot space, you would want a heater that produces 20,000 BTU. You could find a gas fireplace perfect for this task. But there may not be a central heating system available that is small enough. Conversely, if you were heating a 5,000 square foot space, you could use a 100,000 BTU central heating system, but you probably wouldn’t find a gas fireplace potent enough for this situation.

This is one reason why a gas fireplace might not be enough to heat up a room. Now we’ll look at some others.

Reasons Why Gas Fireplaces Might Not Heat Up the Room

Some reasons why your gas fireplace might not heat up the room it’s in include:

  • The fireplace is improperly sized—it is not built to heat this large a space.
  • The chimney is dirty and clogged, restricting airflow to the fire, the strength of the fire, and the efficiency of the fireplace.
  • You are trying to heat a large space or multiple rooms without air flow. A fireplace primarily heats the space directly in front of it; if you are trying to heat not just a room, but a whole home, the fireplace’s heat won’t travel well unless you introduce extra air movement.

Some things you can do to get more heat from a gas fireplace include:

  • Install an appropriate fireplace–with the appropriate BTU output—for the space you intend to heat. (For more on how to size your fireplace, scroll up and read the preceding section about fireplace BTUs.)
  • Clean your chimney and propane vents regularly and professionally. In addition to increasing the efficiency and heat output of your fireplace, it also reduces the risk of chimney fires and the risk of harmful gasses leaking into your home.
  • Use a fireback: a cast-iron slab that absorbs some of the convection heat that your fireplace would otherwise waste and radiates it back into the room, even after the fire is out.
  • Use a chimney fan, which helps pull air out of your chimney, thereby increasing the draft, increasing your fire’s potency, and creating more heat for your home.
  • Use room-to-room fans in a larger space to help the hot air around the fireplace circulate to the rest of your house. You don’t even need any special equipment here, just put any directional fan between rooms and orient it to blow air from one room to the next—and if you have more fans, do the same throughout your house. Orient all the fans to work together to create a path for the air to flow through all of your home.

Is It Cheaper to Run a Gas Fireplace or Central Heat?

Now let’s talk about costs.

Gas central heat is usually cheaper than a gas fireplace. There is a common myth that while central heat would warm a whole house more cheaply, a gas fireplace would warm just one room more cheaply—but this is not true.

If you were trying to heat only one room using central heat, but you left the heat on in every single room, yes, this would be less efficient and more expensive than only running a fireplace because you would be needlessly heating unused rooms.

However, these days, most central heating systems allow you to control their output on a room-by-room basis. So if you want to heat only one room using central heat, you can turn off the heat in the rest of your house, and your gas central heat will be cheaper than a gas fireplace would have been.

Talking about cost gets more complicated when we introduce other kinds of furnaces, such as electric. To compare the cost of a gas fireplace and an electric central heating system, we would have to know the price of electricity in your area. Electricity prices can vary wildly. In general, central heating tends to be cheaper than a gas fireplace, but you’ll have to check your area’s particular electricity costs to know for sure.

Lastly, there is one more consideration that is important to keep in mind. So far, we’ve been discussing the cost of running your heating system, as if it is already in place. However, if you don’t have a heating system in your home yet, you might want to be cautious about adding central heating. Installing a central heating system in your home is incredibly expensive.

If you don’t currently have central heating in your home, adding it may not, in the end, turn out to be cheaper than just running a gas fireplace.

If you already have a gas fireplace, there is one last safety question we should address:

Can You Leave Your Gas Fireplace on Overnight?

Do not leave your gas fireplace on overnight while you sleep. This is very dangerous. Depending on how it’s burning oxygen, your fireplace could release carbon monoxide—which is odorless, invisible, and deadly.

You wouldn’t know the carbon monoxide was filling your home, and it could poison and kill you.

There are a few other good safety measures to always practice:

  • Properly, professionally, and regularly maintain your fireplace—including cleaning the chimney and vents.
  • Have smoke and carbon monoxide detectors in your home and regularly test them to make sure they’re working.
  • Open the flue so that excess carbon monoxide can be vented outdoors.

If you do leave your fireplace running overnight, make sure to take these precautions: make sure your fireplace is properly maintained, make sure you have a carbon monoxide detector and a smoke detector in the same room as your fireplace, and make sure you leave the flue open. But the recommendation is that you never leave your fireplace running overnight, even with these other precautions in place.