Fire pits serve several purposes. They provide a gathering place for socializing, a calming and mesmerizing effect, ambiance, aesthetics, light, and heat. However, depending on a few different factors, a fire pit can accomplish these things to varying degrees.
Heat is perhaps the most important because it’s not relative. While concepts of mood and beauty can change from one person to the next, a rise in temperature is always a rise in temperature. So before you decide on a certain fire pit, it’s good to answer the question: Do fire pits keep you warm?
The fact is that fire pits do keep you warm— to widely varying degrees. Even a candle flame can give you some warmth. Not enough to keep you comfortable— but still. The heat generated by your fire pit depends largely on the fuel source you use (propane, natural gas, or wood). It also depends on the size of the flame, the size of the pit, and what kind of refractory materials you have in the pit to create radiant heat.
Let’s Talk About Heat
In order to understand and make an informed decision about building or purchasing a fire pit, it’s best to know a little something about heat. Most fire pit manufacturers talk in terms of BTUs, which are British Thermal Units. Luckily, you don’t need a degree in thermodynamics to understand BTUs.
The Definition of a BTU
A BTU is the amount of heat energy it takes to raise the temperature of one pound of water by a single degree (Fahrenheit) at sea level. Things get a little complicated when you take into account things like initial water temperature. For our purposes, this definition is just to give you a rough idea of what a BTU is because we’ll be discussing them in regards to fire pits.
Radiation vs Convection
Without going into too much scientific detail (as much as I may want to), let’s touch on the difference between radiant and convective heat transfer.
Nearly all of the heat you feel from a fire is radiant heat. This is because radiant heat is mostly made of visible light and infrared waves. When these photons hit your skin, you feel them as heat.
Convection heat, on the other hand, can travel in all directions— on the air. As a result, most convective heat from flames travels up into the air and is never felt by those situated around the fire. Of course, if the wind blows and the flames bend toward you, you’ll probably feel a gust of convection heat in your face.
This is a good way to lose your eyebrows and a reason why I don’t recommend trying to enjoy a fire on a windy day.
Which Types of Fire Pits Are Hotter?
Determining which types of fire pits are hotter is not the easiest thing to do. Many factors influence the amount of heat any given fire pit is able to produce. The size of the fire pit is the most obvious. Fuel type is another factor. Refractory material in the fire pit is another example. But, to give you a general idea of which fire pit will produce the most heat, we’ll take a look at each of the main types in turn.
Natural gas has a lower BTUs-per-cubic-foot rating than propane. What this means to you is that a natural gas fire pit will use more gas than a similar propane fire pit to achieve the same amount of heat. Natural gas is generally cheaper than propane, so how much you use the fire pit and how warm you want it will determine if you spend more money on natural gas than you would propane.
As a general rule of thumb, natural gas fire pits rated for the same BTUs as a propane tank will give off the same amount of heat. But you’ll burn more natural gas for that same heat.
A small natural gas fire pit will put out somewhere between 30,000 and 40,000 BTUs. A larger one can usually do up to 60,000.
Propane fire pits are rated similarly to natural gas pits. Small ones put out 30,000 BTUs while larger ones can go to 50,000 or 60,000 BTUs. Propane itself tends to be more expensive than natural gas. However, propane fire pits cost significantly less than their natural gas counterparts. Mainly because natural gas tables need to have a dedicated gas line installed by a professional.
The BTUs produced by wood-burning fire pits vary greatly depending on the type of wood you use. Seasoned wood produces more heat than green wood. If you gather your own firewood, it’s best to chop the wood now that you plan on burning next year. However, if you purchase firewood, it’s almost always already seasoned unless otherwise noted.
The kind of wood you used matters, as well. Oak produces more BTUs than Walnut, and Walnut produces more than Pine.
Firewood BTUs are measured per cord in the millions. A cord of firewood is 128-cubic feet. For example, a cord of seasoned, dry beech wood will produce around 27.5-million BTUs. As you can see, it gets a little difficult to determine how much heat your fire will put off without knowing the specific characteristics and amount of wood you’re using. You can look at a chart of firewood BTUs here.
But, the thing about wood-burning fire pits is that you can get them incredibly hot by adding more fuel to them. For this reason, wood-burning pits are considered to be the best bet if you’re looking for heating power alone. Of course, you’re limited by the size of the fire pit, but you can generally get more BTUs out of a wood fire pit that’s the same circumference as a gas fire pit.
How Hot Do Fire Pits Get?
The max BTUs you can get is typically 100,000 on an outdoor fire pit. But 60,000 BTUs is pretty toasty. The average BTUs for a household oven is somewhere between 16,000 and 17,000. Of course, this also depends on where you live. If you’re near the arctic circle, you may want to get as close to 100,000 BTUs as possible.
How Can You Make a Fire Pit Hotter?
Making a fire pit hotter is simple when you’re burning wood: either add more wood or get wood that burns hotter. Or both.
Natural gas and propane fire pits are a little different. Many— but not all of them— come with an air shutter. Here you can control the flow of primary air, which in turn controls the size and color of the flames. The more primary air, the smaller, bluer, and cleaner the flame burns. These small, mostly blue flames give off more BTUs than their larger, yellow brethren.
Best BTUs for Your Bucks
Below is one of each type of fire pit that you can choose from. They’re all highly rated and are capable of high BTUs. But keep in mind that the wood fire pit’s output depends on your efforts in regards to proper fuel for maximum heat.
At 45,000 BTUs, this rectangular natural gas fire pit can keep plenty of people warm. The pit itself is 60” by 27” by 17”, with a 30” long fire area. It comes with lava rocks for added radiant heat and has a great concrete look to it. Check out the Elementi Granville Fire Table.
50,000 BTUs from this inexpensive fire table is great value for your buck. The nice thing about this one is it has a built-in place to hide your propane tank, so you don’t have to worry about tripping over it or having it as an eyesore. Check out the Tacklife Propane Outdoor Companion.
Amazon Basics offers a nice, inexpensive wood-burning fire pit. It stands up off the ground so you can be closer to that radiant heat. The fire bowl is 22” in diameter. Pair this fire pit with some seasoned beech, mesquite, or applewood and you’ll be chasing away the cold. Check out this wood-burning fire pit.
Alternative to Fire Pits
If you’re just looking to provide you and your guests with maximum warmth in the cold months, you may consider an alternative to a fire pit. You won’t have the benefit of flames with these outdoor heaters, but you’ll stay plenty warm from the radiant heat they provide.
Stand-Up Propane Heater
At 46,000 BTUs, this propane heater stands 88-inches tall and comes with a cover. It’s designed for commercial use but it will do just fine on your back patio. Check out this Pamapic Patio Heater.
Determining just how warm fire pits can get involves many variables and no small amount of science. Now that I’ve gone through all the technical stuff, I’ll try to sum it all up here.
For more control and overall higher heat possibility, a wood-burning fire pit is the way to go. With the right wood that has been seasoned, you can keep warm as long as you have fuel to burn.
However, if wood-burning is illegal or banned where you live, propane fire pits require less upfront cost and better efficiency. Plus propane fire pits are portable, to varying degrees. The only issue is that you have to replace the tank every so often.
Natural gas fire pits are expensive to purchase and install. But, since this fuel is piped directly to your home, you don’t ever have to worry about running out.
Ignoring all other factors, natural gas and propane can provide you with the same amount of heat, given the fire pits are rated for the same amount of BTUs, but it’s hard to beat the power of wood in providing heat.