An outdoor fire pit is a great way to enjoy your backyard or patio. They are perfect for entertaining guests or just relaxing on a cool evening. One thing you need to be aware of when using a propane fire pit is how much propane it uses.
An outdoor firepit uses between 1.86 and 2.78 lbs (0.22 to 0.33 gal) of propane per hour. The higher the firepit’s heat output, the higher the combustion rate. For instance, a 60,000 BTU/hr firepit consumes propane faster than a 40,000 BTU/hr pit.
This post will describe how to determine the amount of propane your fire pit uses in 6 easy steps. I’ll also mention the factors that can affect how much propane your fire pit uses and provide a table with approximate usage for different-sized propane tanks. Stay tuned!
How To Determine the Amount of Propane a Firepit Uses
Calculating how much propane an outdoor fire pit uses isn’t as complicated as most would think. With the right steps, you can easily determine the amount of propane used for your fire pit.
Here’s how to do that:
1. Determine the BTUs per Pound of Propane
The first step in calculating the amount of propane used by your fire pit is to determine the BTUs per pound of propane. In simple terms, BTU stands for British Thermal Unit and is a unit of measurement for the amount of energy released when burning fuel.
One BTU is the equivalent of burning one match, typically 1055 Joules. The higher the BTU per pound, the more fuel efficiency. A common BTU rating for propane is approximately 21,548 BTUs per pound.
The BTU rating is usually listed on the specification sheet that came with your fire pit. If you can’t find that sheet, you can also look up the BTU rating online or contact the manufacturer.
2. Determine the Capacity of the Propane Tank in Pounds
The next step is to determine the capacity of your propane tank in pounds (or gallons). You can find this information on the specification sheet or by contacting the manufacturer.
That said, it’s important to note that when determining tank capacity, you should measure it in full pounds or gallons. One gallon of propane weighs approximately 8.34 pounds, so if your tank has a capacity of 2.4 gallons, it would have a capacity of approximately 20 pounds.
3. Determine How Many BTUs the Tank Can Produce
Once you have the BTU rating and the capacity of your tank, you can calculate the maximum BTUs that your tank can produce. To do that, multiply the BTU rating by the capacity of the tank.
For example, if a propane tank has a capacity of 20 pounds (2.4 gallons) and a BTU rating of 21,548, the maximum BTUs it can produce is 431,000 (20 x 21,548).
Similarly, if a propane tank has a capacity of 40 pounds (4.8 gallons) and a BTU rating of 21,548, the maximum BTUs it can produce is 862,000 (40 x 21,548).
4. Determine How Many Hours Your Fire Pit Runs on One Tank
The next step is to estimate how many hours your fire pit will run on one tank. To determine that, you need to divide the number of BTUs the tank can produce by the BTUs per hour that your fire pit uses.
Additional methods of estimating the burn time of a propane tank include:
- Tracking your propane usage: Tracking how long it takes for your propane tank to be depleted is the more accurate method. However, it may take several days or months since that will require you to monitor and track the usage of your fire pit constantly.
- Asking for an expert’s opinion: If you purchased your fire pit from a retailer, they might have an estimate of the burn time for a specific size of the propane tank.
- Checking estimates on online forums or blogs: Remember that these estimates can vary and may not be as accurate as tracking it yourself or referring to the manufacturer’s estimation.
With any of these methods, you can have a better idea of how long your fire pit will run on one tank.
5. Divide 80% of the Tank’s Weight by the Number of Hours It Lasts
Now that you have determined the capacity of your propane tank and how long it will last, you can calculate how much propane your fire pit uses per hour.
To do that, take 80% of the weight of your propane tank and divide it by the number of hours it lasts.
Using the previous example, if a propane tank with a capacity of 20 pounds lasts for 10 hours, then your fire pit uses 1.6 pounds of propane per hour (80% x 20 pounds divided by 10 hours).
Knowing how much propane your fire pit uses per hour can help you determine the cost of using your fire pit and allows you to budget accordingly. Besides, it can also help you plan ahead and ensure that you have enough propane on hand for your outdoor gatherings.
That said, here’s a table that summarizes how much propane your fire pit may use per hour based on the capacity of your propane tank and the estimated BTU/hr rating:
|40,000 BTUs/hr||50,000 BTUs/hr||60,000 BTUs/hr|
|5 Pounds||1.86 pounds/ hour||2.33 pounds/hr||2.78 pounds/hr|
|20 Pounds||1.86 pounds/ hour||2.33 pounds/hr||2.78 pounds/hr|
|40 Pounds||1.86 pounds/ hour||2.33 pounds/hr||2.78 pounds/hr|
|60 Pounds||1.86 pounds/ hour||2.33 pounds/hr||2.78 pounds/hr|
|100 Pounds||1.86 pounds/ hour||2.33 pounds/hr||2.78 pounds/hr|
These estimates are based on the assumption that your propane tank is filled to 80% of its capacity.
For example, a 5-pound tank would be filled with 4 pounds of propane:
- A pound of propane gives 21,548 BTUs
- A 5-pound tank is usually filled with 4 pounds of propane
- Therefore, at 80% capacity, the tank gives 4*21,548 = 86,192 BTUs.
- At 40,000 BTUs/hr, the 5 pound tank runs for 86,192/40,000 = 2.15 hrs. Therefore, the fire pit uses 4/2.15 = 1.86 pounds of propane per hour
- At 50,000 BTUs/hr, the 5-pound tank runs for 86,192/50,000 = 1.72 hrs. Therefore, the firepit uses 4/1.72 = 2.33 pounds of propane per hour
- At 60,000 BTUs/hr, the 5-pound tank runs for 86,192/60,000 = 1.44 hrs. Therefore, the firepit uses 4/1.44 = 2.78 pounds of propane per hour
Note: The estimates above are based on an assumption that no external factors, such as wind and drafts, are present.
From the table, the propane combustion rate per hour only increases with the BTU output of your firepit. As you can see, it doesn’t vary with tank size. However, expect a larger tank to last longer at a specified heat output.
Factors That Determine How Much Propane Your Fire Pit Uses
Now that you know the steps in determining how much propane your fire pit uses, it’s also important to consider that there are factors that can affect this usage.
Wind and Drafts Can Reduce Burn Time
A roaring fire is a perfect way to enjoy a cool evening, but wind and drafts can quickly put a damper on your plans.
As anyone who has ever lit a candle knows, flames are sensitive to airflow. When the flow of air increases, the flame burns hotter and taller. The same is true for fires in a fire pit. If the wind picks up, the increased airflow can cause the flame to burn hotter and use more propane.
In addition, drafts from nearby doors and windows can also affect the burn time of your fire.
That said, high winds can increase the risk of embers flying out of the fire pit and starting a fire, so consider avoiding using your outdoor fire pit during windy conditions.
A Fire Pit With a High BTU Output Will Use More Propane
In the steps above, I mentioned that the BTU rating of your propane tank and your fire pit can affect how much propane it uses.
A higher BTU rating means that the fire pit can produce more heat. Thus, a fire pit with a high BTU output will use more propane than one with a lower BTU rating.
If you’re looking for a fire pit that will use less propane, consider one with a lower BTU rating.
Frequency of Use Can Affect Propane Usage
The more often you use your outdoor fire pit, the more propane it will use. That’s just a simple fact, as using your fire pit daily will deplete the propane tank faster than using it less frequently.
However, this also means that if you plan on using your fire pit regularly, investing in a larger capacity propane tank may be more cost-effective in the long run.
That said, if you’re just starting out with firepits, I recommend checking out this BALI OUTDOORS Propane Fire Pit (link to Amazon.com). It features a firepit table design that blends in perfectly with your outdoor furniture, and it has a BTU output of 60,000. Plus, it comes with fire glass for a more visually appealing flame. Additionally, you can check our post about the best tabletop and mini fire pits for indoors and outdoors.
While there’s no one-size-fits-all answer to how much propane your outdoor fire pit uses, following the steps above and considering any factors that can affect usage can give you a better idea of what to expect.
And with a little planning, you can enjoy cozy fires in your backyard for many seasons to come.