It costs approximately 80 cents to $11 an hour to operate a gas fire pit, depending on the Btu rating of the appliance and the type of gas it uses. Propane is more expensive than natural gas at about 65 cents per 1k Btu versus 12 cents per 1k Btu for natural gas.
What the Heck Is a Btu?
If you aren’t familiar with “energy speak”, let’s do a little decoding first so the following will make more sense to you.
Btu (British thermal unit) is a measurement for heat energy. One unit represents the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. (If you want to get really technical, it’s actually one pound of liquid water at its greatest density, approximately 39 degrees Fahrenheit.)
HOW HOT is one Btu? The U.S. Energy and Information Administration likens one Btu to the energy released by a burning match.
Using Btu as a measurement tool is a good way to translate different fuels into the “same language” so they can be compared on an equal basis.
Therm (TH) is the industry standard of measurement for natural gas. One therm is equal to 100,000 Btu and roughly equivalent to 100 cubic feet of natural gas.
Propane is typically measured in gallons. One gallon of propane is equal to about 91,600 Btu.
Using Btu allows us to compare the costs of these fuels, which are sold using different methods of measurement.
Comparing the Cost Per Hour of Propane vs. Natural Gas
The cost of operation depends on a number of factors that we’ll discuss later in this article, but you will find a good baseline below.
The Btu rating for an appliance denotes the maximum heat output for that device. (You should be able to find the Btu rating for your appliance on the attached tag.) The following calculations are based on running that device at its maximum output for an hour.
|Fuel Type||Fire Pit Btu Rating Cost Per Hour|
|65,0000 Btu||90,000 Btu||125,000 Btu||165,000 Btu|
|Natural Gas||$0.80/hour||$1.10/hour||$1.53/hour||$ 2.02/hour|
|Propane (refillable tank)||$4.23/hour||$5.86/hour||$8.14/hour||$10.74/hour|
How to Calculate Your Actual Cost
The above numbers represent a ballpark cost. If you want to get into the nitty-gritty and know exactly how much it costs to run a particular appliance using the going rate for gas products in your area, we’ll show you how to do that.
Even if you aren’t a “numbers” person, you should be able to follow along. If you get lost; we’re always happy to help.
Grab your natural gas bill and a calculator. Look for the total therms (TH) listed on your bill for the month. We want to find the cost per Btu, so we have to “translate the language.”
Step One – Converting from TH to Btu
1 TH = 100,000 Btu
So we’ll first need to multiply the number of therms listed on your bill by 100,000.
Let’s say you used 250 TH for the month. Your equation would look like this:
250 x 100,000 = 25,000,000 Btu (used for the month)
Step Two – Finding Cost per Btu
What was your cost for this month? Let’s say it was $300 for the 250 TH.
We’ll now divide 300 by the number of Btu to get the cost per Btu.
300 ÷ 25,000,000 = .000012 cents (per Btu)
Step Three – Finding Hourly Cost for Your Natural Gas Unit
To find the cost of running your appliance, we’ll need to know the Btu for your burner. If you’re not sure what the rating is, you can find it on the tag.
Let’s say it has a rating of 65,000 Btu.
You’ll multiply the cost per Btu times the rating. So keeping with our example, it will look like the following:
65,000 x .000012 = .78 (cents per hour)
Now you have some idea of what it will cost to enjoy an evening of fun around the fire pit. If you have the flame turned up to its maximum, you are spending about 80 cents an hour to run your natural gas fire pit. If you have the flame turned down, this cost will be less.
1. Converting A Tank of Propane to Btu
A portable tank of propane is sold by weight, not by gallon. And, it’s important to note that a 20-pound tank is not likely to have 20 pounds of gas in it. Propane expands with heat, so most refilling stations only put 15 pounds of gas in a 20-pound tank to allow for expansion.
For this example, we’re going to assume the tank is 15 pounds and that means it has approximately 3.5 gallons of gas in it. (To get an accurate measure of your costs, you should check with your refilling station to find out what they use as their maximum fill.)
One gallon of gas equals approximately 91,600 Btu.
91,600 x 3.5 = 320,600 Btu (per 15-pounds of gas)
2. Calculating Cost Per Btu
If the tank cost $21, we can determine the cost by dividing the total cost by the total number of Btu.
21 ÷ 320,600 = .0000655 cents (per Btu)
3. Finding Hourly Cost for Your Propane Unit
Using the Btu rating for your burner, we can now calculate the hourly cost.
65,000 (Btu rating) x .000065 = 4.22
The hourly cost to use this propane fire feature for one hour is $4.22.
An additional number you may be interested in, is how many hours of operation can I get from one tank of gas?
We simply divide the total Btu per tank by the btu rating of your appliance.
320,600 (total btu per tank) ÷ 65,000 (Btu appliance rating) = 4.9 hours. So, you’ll get approximately 5 hours of enjoyment per tank.
How to Reduce Operating Costs
-Thoughtful Design. Bigger isn’t always better. Think through how you plan to use your fire feature—large parties or intimate gatherings? Also, consider the space you have available for it. If your seating area only accommodates a small grouping, you won’t need a mega burner. Size your gas fire feature according to your outdoor space and how you plan to use it.
-Reduce Flame Size. You don’t have to crank up the flame as high as it will go to have a good time. A lower flame gives off plenty of heat and still creates a nice atmosphere while helping to reduce fuel usage.
-Turn Off the Tank. If using propane, be sure to turn off the gas with the knob located on the top of the tank whenever it’s not in use. This will prevent accidental leakage, which can slowly empty your tank. It’s a quick and easy step. Not only will it save money, but it will also save you from the disappointment of gearing up for an evening of entertainment only to discover there is no gas in the tank.
-Add Heating Pads. Consider getting a few heated, stadium seating pads for your chairs. There are styles that can be heated in the microwave and stay warm for several hours allowing maximum flexibility. It’s a low-cost option to help keep you and your guests comfortable in cold weather without boosting the flames.
EXTEND the season! Spring and fall can offer up some pretty chilly nights. In this kind of weather, whatever side of your body is not facing the fire, can feel like it’s freezing. Heated seating pads can solve the issue of uneven heat distribution allowing you to enjoy your fire pit well beyond the summer months.
Call Us with Your Questions
If you’re having difficulty calculating the appliance size that would be best for your space and entertainment goals, please contact us. Our highly trained support staff would be happy to walk you through the design options.