Fire Pit BTU 101: Understanding Heat Output for Your Outdoor Space
Fire pits are a great way to add ambiance, warmth, and a touch of class to your patio, deck, or outside entertainment space. Fire pits are rated in BTUs similar to popular fire pits, which determines their heating effectiveness. What BTU rating should you look for when selecting a fire pit for your home?
Takeaway: A good BTU for a fire pit is between 40,000 and 50,000 BTU for a small to medium space and up to 200,000 BTU for a large outdoor space. The right BTUs will depend on the size of the space being heated, how sheltered the space is, and how cold your atmospheric temperatures get.
Fire Pit tables are a good choice for extending the time you can make use of your outdoor space, especially in the cooler months. Understanding the BTU rating standard and how it pertains to fire pit will help you make the right choice for your outdoor area.
What BTU Should You Look For In A Fire Pit?
Many of us are familiar with the BTU rating of home appliances such as air conditioners and indoor heating systems, but what about outside heating appliances?
What is the method to establish the right capacity fire pit to suit your outdoor heating and entertaining requirements? The key to making the right fire pit choice is understanding the BTU rating and how you can interpret this standard for a gas fire pit.
What Is A BTU?
BTU is an acronym for British Thermal Unit and measures heat or energy. When the BTU was developed, it was calculated as the amount of heat needed to raise the temperature or 1-pound of water by 1°F.
The BTU has become the accepted standard when rating the heating power of appliances that output heat as one of their primary functions.
We have more detailed information on BTUs in a previous article, “Propane vs. Natural Gas Fire Pits — Everything You Need to Know.”
The BTU rating of your gas fire pit will affect its heating power and the height of the flame. Fuel type is an important consideration when investigating BTUs for fire pits since different fuels will provide different BTUs with varying levels of efficiency.
BTU In Relation To Flame Height
The fire pit flame height, as well as the flame appearance, will be affected by the BTU and several other factors.
A tall flame is usually associated with a higher heat output, but the height of the flame is not the only factor affecting the BTU output.
The color of the flame will be an indicator of the heat being generated by the flame. An orange flame may look great and deliver a better ambiance, but a blue flame will generate better heat output.
The higher the BTU rating of the gas fire pit, the larger the flame you will get from the burner. However, the amount of air mixed into the gas prior to the burn will affect the color of the flame and thus the final heat output or BTU of the fire pit.
BTU & Fuel Types
The type of fuel used in a fire pit or any other heating appliance will affect the BTU rating since fuels burn with different intensities.
Most fuel types will offer a range of BTUs since the quality of the fuel can change, or you can increase or decrease the number of burners to achieve a different BTU rating.
Wood Burning Fire Pit BTUs
Wood burning fire pits will have a wide range of BTUs because the amount of heat the table can put out will depend on the type of wood burned and the size of the space in the table where the wood can be burned.
Hardwoods will generate a higher BTU than burning softwoods on the fire pit. The larger the space to burn wood on the fire pit, the larger the fire you can make, and the more BTUs can be generated. Consequently, you can expect a wood-burning fire pit to generate anywhere from 30,000 BTUs to 100,000 BTUs.
Natural Gas Fire Pit BTUs
Natural gas typically has a lower BTU than other gases because it burns with a lower intensity and, therefore, less heat generation.
Natural gas is piped to some homes in certain areas and may be a viable option for some people. The main disadvantage with piped natural gas is the lack of portability of the fire pit since a pipe is laid to bring the gas to the table. The BTU ratings for natural gas-fueled fire pits are typically between 30,000 and 60,000 BTU.
Bioethanol Fire Pit BTUs
Bioethanol fire pit produce a real flame, but the flame does not burn as hot as other fuels. The result is a lower BTU rating for tables that burn this fuel.
This limitation makes bioethanol fire pits more appropriate for indoor use than outdoor use. The BTU rating for bioethanol fire pits ranges from 20,00 BTU to 28,000 BTU.
Propane Fire Pits BTUs
Propane is a popular fuel for gas fire pits and fire pits because it is relatively cheap compared to other gas fuels, burns with more intense heat, and has a clean-burning flame.
One of the main attractions of propane-fueled fire pits is portability. The propane is usually supplied via a gas cylinder, which can be hidden from view on the side of the propane fire pit, but allows the fire table to be moved to where it is needed.
Propane fire pits have the added advantage of generating between 40,000 and 150,000 BTU, making them efficient and effective for heating a wide range of spaces.
How Many BTUs Is Good For A Fire Pit?
When you are working out how many BTUs your outdoor fire pit should have, there are several factors you should consider.
The size of the outdoor space you need to heat will be the main consideration because more BTUs are required to heat larger spaces.
Other factors you should consider are your general climate temperatures, how sheltered the space is, and how close you sit to the fire table.
Is 30,000 BTU Good For Fire Pit?
A fire pit that generates 30,000 BTU is on the lower end of the BTU rating for fire pits, but they have value for certain heating requirements.
A 30,000 BTU fire pit will generate enough energy to heat a 350 sq ft area. This would be ideal for an indoor application assuming you’re using bioethanol as your fuel source, but outdoors, the space would need to be well sheltered from the wind, and preferably with a roof for the heating to be effective.
In this low BTU range, you have a choice of fuel types, depending on the location of the fire pit and your preference.
Wood would be a good fuel choice for an outdoor fire pit of 30,000 BTU, provided your local regulations allow for open fires. Natural gas is a good option for a constant supply and propane for better portability. Bioethanol is a good choice for a clean-burning fuel, but at 30,000 BTU, it would be expensive to run.
Bioethanol is more expensive because the manufacturing process is more costly, and the flame does not burn as hot as natural gas or propane. This results in burning more bioethanol than propane or natural gas to heat the same space.
Is 40,000 BTU Good For A Gas Fire Pit?
40,000 BTUs is a good average output table that will offer very good heating for indoor or outdoor applications.
Even though a 40,000 BTU gas fire pit has only 10,000 BTU more than a 30,000 BTU table, it has almost one and a half times the heating capacity the latter. The stronger flame produced by the 40,000 BTU table generates a heat output that feels warmer much faster.
A 40,000 BTUs can effectively heat a 550 sq ft area, and its heating capacity is less affected by wind and lack of roof cover over the space.
A fire pit with 40,000 BTU output is generally more appropriate for an outdoor space than an indoor space unless you have a large room you want to heat. If you use this fire pit indoors, you should stick to using bioethanol as the fuel source due to its safer emissions.
When you get up to this level of BTU output, your fuel choice becomes more limited, especially factoring in the fuel costs.
Wood-burning fire pits capable of generating 40,000 BTU would only be safe for an outdoor installation. Bioethanol is out of the question as a suitable fuel for this size fire table since it cannot generate this level of BTU output.
The best fuel choice for a 40,000 BTU fire pit would be either natural gas or propane, with propane being the most popular choice from a portability and cost aspect.
Is A 50,000 BTU Fire Pit Table Warm?
A fire pit generating up to 50,000 BTU will be very warm if you sit close to the table and can heat up an area between 675 sq ft and 700 sq ft.
The distance from the 50,000 BTU fire pit at which you will feel comfortably warm on a cold evening outdoors is between 8 and 10 feet. You will still be able to feel the heat further away from the table, but it will be less effective at keeping you comfortably warm.
From the gas-fuelled fire pit options, a natural gas source would work, but, at 50,000 BTU, it is reaching the upper level of its heating capacity.
Propane would be the best fuel choice for a fire pit at this level of heat output. It is a cheaper and a more effective heating option.
40,000 Vs. 50,000 BTU Fire Pit
Choosing the right BTU gas fire pit can make the difference between a disappointing heating experience and a warm, snug entertainment area.
The 40,000 and 50,000 BTU versions are the most common gas fire pit heat outputs. Comparing these two fire pits may help you make the right choice.
Sheltered heating area
550 sq ft
675 to 700 sq ft
Outdoor heating range
Up to 8 feet from the table
Up to 10 feet from the table
Natural gas or propane
$500 - $1,700
$500 - $1,900
Given that you can purchase a 50,000 BTU fire pit for a similar price as a 40,000 BTU fire table, you may consider going with the higher capacity BTU, but this is not always the best choice.
In a small space, a 50,000 BTUs may become too warm, making the space uncomfortable and difficult to find a happy medium.
A 50,000 BTU fire table would be a more appropriate choice for an outside space with less shelter, but a 40,000 BTU version would make more sense for a smaller or well-sheltered outdoor space.
A 50,000 BTU fire table would have a higher running cost than its 40,000 BTU counterpart. A 40,000 BTU fire table could use more fuel than a 50,000 BTU table if you are using it to heat a space that is too large. In this case, you will be running the table in its highest setting permanently to heat up the large space, which will use more fuel in the long run.
What Is The Highest BTU Fire Table?
The highest BTU fire tables can generate up to 200,000 BTU, which would cover an area of about 3,000 sq ft.
These large output fire tables are necessary for large outdoor spaces and locations that have very cold temperatures. These units would overwhelm small spaces, and the cost of fuel for these fire tables can become high, depending on the frequency of use and how high the burners are turned.
In most cases, people want to sit close to a fire table to experience the cozy ambiance, which would be difficult to do with a 200,000 BTU fire table!
Fire tables are not purely functional but offer a classy and elegant means to heat an outdoor space such as a deck, patio, or entertainment area.
Choosing a fire table with an appropriate BTU rating for your outdoor area will give the most effective heating while keeping the running costs to a minimum.