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There’s a lot to consider when buying a heater for your outdoor space.
It would be great if the only concern was looks, but it’s much more than that. One of the biggest concerns is the amount of fuel you can expect to use.
Today I’ll be answering the question how much propane does an outdoor heater use. Plus some other useful information.
Most portable propane patio heating units have a 20lb tank and hold about 4.7 gallons of propane, but for safety reasons, they’re only filled to 80% capacity—about 16 lbs. 20lb tanks can last up to 10 hours, and refills can cost between $3.25 to $4 per gallon.
Read on, and I’ll cover more about the usage and cost of propane heaters.
How Long Will A 20lb Propane Tank Last?
First off, that’s a bit like asking how long is a piece of string.
I’m going to delve into some math here to explain, so bear with me.
There is no single answer to this question because there are variables that need to be taken into account. If you were paying attention to what I said above, you’ll get a hint. I said a 20lb propane tank can last up to 10 hours, not that it will.
Many, but not all propane patio heaters will have heaters that produce in the area of 40,000 BTUs (British Thermal Units) per hour. So if that’s the case for your heater, you can expect your fuel to last about 10 hours—if you have it set to the highest setting. If you aren’t using the highest setting, it will last longer.
But what if your patio heater puts out 50,000 BTUs? Will your tank still last 10 hours? Nope!
A 50,000 BTU tank will burn faster, and a 30,000 BTU tank will take longer.
Calculate How Much Propane Your Heater Will Use
Let’s figure out how much propane an outdoor heater uses.
- Find out the weight of your empty tank. It may be called tare weight and should be somewhere on a label on the tank.
- Subtract the tare weight from the weight of a full tank.
- Divide the total weight of the full tank by 4.24 which is the weight in pounds of one gallon of propane.
- One gallon of propane burns 92,000 BTUs in an hour. If you have a 50,000 BTU patio heater, each gallon will burn for 1.84 hours. (92,000 BTUs per gallon/50,000 a 50,000 BTU rated heater = 1.84)
The above calculation will provide you with the burn rate of your propane heater.
Now, to calculate how long it will burn for, you need to do the following.
Assuming your heater is rated at 40,000 BTUs a 20lb tank will burn for:
- 2.3 x 4.24= 9.752 hours
Assuming your heater is rated at 60,000 BTUs a 20lb tank will burn for:
- 2.3 x 4.24= 6.5 hours
Okay, I ended up doing the math for you after all!
Propane vs Electric Heaters – Running Costs
Now that you have a clearer idea of how much propane your outdoor heater will use, it might lead you to another question.
What about electric heaters? Would it be more cost effective to go that route instead of propane?
On the surface, if you were to do a comparison of the price you pay locally for electricity per kilowatt hour and the cost of propane, it may seem as though electricity is cheaper.
However, dig a little deeper and you will see the answer is more complex. Because the cost is dependent on the appliance in use. Since we’re interested in heaters, let’s focus on that.
Assuming you run a 2,500 watt electric heater for 8 hours a day, you’re looking at about 20kWh. The same heater would use .068 gallons of propane in that time frame, which is the equivalent of 8530 BTUs per hour.
In the above scenario, a propane heater is 20% cheaper to run.
But here’s another math problem for you. The upfront costs of a propane heater—any gas heater, really—can be double the cost of an electric heater. However, assuming the heater doesn’t die on you a few months after you purchase it, in the long term, the propane heater will still save you money.
What Size Propane Heater do you Need?
Most patio heaters will measure heat in BTUs and will list the heating area of feet around the heater.
When buying propane heaters, you need to consider the size of the tank as well. Smaller tanks are going to need to be replaced more often, and if you’re buying a heater with greater BTUs, it will probably have a bigger tank.
Tanks sizes on patio heaters typically range from 20 to 40 pounds.
Don’t assume the bigger tank and greater BTUs are going to be the answer. If you have a tiny patio to heat, buying something designed to heat a huge space will work against you. Figure out what means the most to you and then find a balance between space and power when choosing your heater.
You can do that by taking the total number of BTUs and dividing it by 40 if you live in a more temperate climate or 30 in colder climates. This calculation will help you determine how well the heater will cover your square footage.
Since I live in a cold climate, I would, for example, do this.
40,000 BTUs / 30 = 1,333 square feet.
That’s a very big patio.
How Many BTUs Does Your Patio Need?
No matter how amazing your patio looks, it’s size matters. A larger patio needs a larger amount of heat. Here’s a quick table to give you a rough idea.
|100-150 sq. ft. or ~9-14 sq. meter||5,000 BTUs|
|150-250 sq. ft. or ~14-32 sq. meter||6,000 BTUs|
|250-300 sq. ft. or ~32-28 sq. meter||7,000 BTUs|
|300-350 sq. ft. or ~28-32.5 sq. meter||8,000 BTUs|
|350-400 sq. ft. or ~32.5-37 sq. meter||9,000 BTUs|
|400-450 sq. ft. or ~37-42 sq. meter||10,000 BTUs|
|450-550 sq. ft. or ~42-51 sq. meter||12,000 BTUs|
|550-700 sq. ft. or ~51-65 sq. meter||14,000 BTUs|
|700-1,000 sq. ft. or ~65-93 sq. meter||18,000 BTUs|
Are Propane Patio Heaters Worth It?
In a word, yes!
Propane patio heaters come with several benefits:
- They’re easy to set up and easy to maintain
- You can choose permanent or portable models
- They’re available in a full range of sizes from small hanging heaters to full-sized, free-standing models
- Most portable styles house the propane tank inside the base of the heater
- Full range of safety features
- Propane is non-toxic so it won’t harm the water and soil in your yard—hooray for you gardeners!
- You can choose to have one professionally installed for permanent use
I’ve thrown a lot of math and numbers at you, but by now you should have a solid answer to the question how much propane does an outdoor heater use.
Assuming you’re running your propane heater at full heat, a:
- 40,000 BTUs patio heater with a 20lb tank will burn for 9.752 hours
- 50,000 BTUs patio heater with a 20lb tank will burn for 7.80 hours
- 60,000 BTUs patio heater with a 20lb tank will burn for 6.5 hours
And since propane burns efficiently it costs less to run your heater than it would if it were an electric heater. So even though it costs more to purchase a propane patio heater, in the long run, it will be cheaper.
Keep all that in mind when you’re narrowing down your choices, and you’ll be loving your nice warm patio on those cool autumn nights.
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