How Much Heat Do Patio Heaters Give Off

How Much Heat do Patio Heaters Give Off?

You’ve invested a lot of time, effort, and money into creating and perfecting your patio. With great evenings spent outdoors with friends, family, and guests you’d like to extend your time on your patio as much as possible before the mercury drops close to zero. You may have asked your local DIY shop experts and done some research into ways to keep you and your guests tasty warm to enjoy the outdoors that bit longer and you’ve learned that patio heaters are the answer. Now you’re wondering how much heat do patio heaters give off – and we have the answer for you.

Patio Heater
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 Patio heaters give off heat in a range typically from 5,000 BTU to 50,000 BTU. A typical full-size free-standing patio heater has a rating of 40,000 BTU which can sufficiently heat an uncovered patio area of 65 sq ft to 100 sq ft by raising the temperature in that area by 10 to 20 degrees Fahrenheit.

Patio heaters are available in a wide variety of designs, are powered by different fuel sources, and are available across price ranges to suit any style and budget. Many factors affect the heat ranges of patio heaters in their performance and efficiency. The size of your patio area and the arrangement of your patio furniture plays a significant role in determining the type of heater and the heat range you will need. By reading further, you’ll learn about everything that affects how much heat patio heaters give off.

How do Patio Heaters Work?

To learn how much heat patio heaters give off, you need to first understand how heat is measured and how patio heaters work. When researching for patio heaters, you will have seen them advertised with something like “20,000 BTU” and wondered what that is. BTU stands for British Thermal Unit: this is the standard measurement unit for heat. It is calculated as the energy required to heat or cool one pound of water by 1 degree Fahrenheit at sea level. Think of it in another way: 1 BTU is equivalent to 1 standard matchstick’s heat output. For patio heaters, BTU indicates the amount of heat that the heater emits: the higher the BTU number, the greater the heat output.

How Patio Heater Works
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Here is a caveat, however. Not all patio heaters of the same BTU rating emit the same amount of heat. It is due to the design, materials, and efficiency of patio heaters that determines the amount of heat it emits, more so than its BTU rating. This is down to how they emit their heat: most heaters function by blowing hot air around it (which sees the heat dissipate quickly between you and the heater), while radiant heaters heat nearby objects (such as people and furniture) as the heat travels through the air in much the same way as sun’s rays do (minus the harmful UV rays and other dangerous effects).

Types of Patio Heaters

As we have established, there are different types of fuel sources and designs of patio heaters. Each fuel source brings benefits and drawbacks, while the design of patio heaters determines how much heat it gives off and how much of an area it can heat too.

Different Types  Of Patio Heater
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The most common types of fuel sources for patio heaters are propane gas, natural gas (such as LPG), wood-burners, and electrically-powered. Most households feature propane gas-powered or electric-powered patio heaters as these are the most typically available sources for most areas.

Manufacturers stick to four designs and styles: free-standing patio heaters; tabletop patio heaters; mounted patio heaters; and, hanging patio heaters. Most patio heaters are made from stainless steel or aluminum. If you live near any water areas such as lakes, dams, or the sea, you’ll need to bear this in mind to search out a coated stainless steel patio heater.

As we have mentioned, the design and fuel source of patio heaters affects their heating ranges and efficiency. A patio heater with a high BTU rating isn’t recommended for heating small patio spaces: propane and natural gas emit toxic and poisonous vapors that are harmful to people and if those gases are confined to a small space they will be unable to ventilate the area sufficiently to avoid dangerous health consequences.

What size patio heater do you need?

This is the most often asked question regarding patio heaters and the answer isn’t as straightforward as you may think. There are several factors to consider:

Size of Patio Area

The rule of thumb regarding patio heaters and the size of patio areas is that 1 heater can heat 1500 to 2000 sq ft of a covered patio; 1 heater can heat 100 sq ft of an uncovered patio.

Positioning of Patio Heaters

You might not be able to heat your entire patio area – nor would you want to if you only have people seated in one corner of the entire area. By placing patio heaters only in areas where people meet or where your seating is arranged will boost the effectiveness of the patio heater and reduce wasted resources heating areas where there is no foot traffic.

Number of Patio Heaters

To determine how many patio heaters you will need to heat your patio, you will first need to calculate the size of the area you want to be heated, such as around a table, seating, or barbecue grill. As we have established, a patio heater with a high BTU might be able to theoretically heat a large area but its heat range varies according to the design and overall efficiency of said patio heater. It is wiser to rather make use of two patio heaters of lesser BTU ratings to focus heat ranges rather than use one patio heater with a high BTU rating but the heat dissipates before it reaches people.


Patio heaters’ performance and efficiency are affected by wind. The placement of and design of a patio heater determines its wind-resistance, in the way it can heat a surrounding area when there is a light breeze. To counteract that, many people use a wind-breaker device to ensure the heater is as unaffected by the wind as possible.

How much heat do patio heaters give off?

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Now that we have outlined the various factors that determine the performance and efficiency of patio heaters, we can list the heat range that different types of patio heaters give off:
1) Free-Standing patio heaters typically give off 40,000 BTU which can heat a patio area of 2000 sq ft. These types of patio heaters are popular thanks to their heating performance, their fuel source commonly used is propane gas, and being mobile units that are easily wheeled or carried to areas where they are required.
2) Mounted patio heaters are commonly installed to ceilings and walls. These are permanently fixed and are mostly infrared heaters powered by electricity and they free up floor space thereby making them ideal for small patio areas. As they are often smaller in size to free-standing patio heaters, most people use 2 or 3 in strategically placed positions to direct the heat to seating areas and where most people assemble on their patios. These types of heaters are also fitted with control options for users to vary the heating according to their needs and the air temperature around them. Typically speaking, these types of heaters have a BTU rating from 10,000 to 30,000.
3) Tabletop patio heaters are tiny and are designed for heating very small and specific areas. Having said that, some models available have a heat rating of up to 30,000 BTU.
4) Hanging patio heaters are used most in covered patio areas and under gazebos. These range in heat performance from 10,000 to 30,000 BTU.

Most patio heaters are equipped with control options. These are usually 2- or 3-stage control systems that regulate the heat output and improve their usage efficiency. Single-stage heaters are either fully on or fully off; 2- and 3-stage heaters have controls to vary the heat output in degrees, such as 30-, 50-, or 100-percent on, and fully off.

How to Calculate the Size of Patio Heater Needed?

To calculate the size of the patio heater needed to heat your patio to keep you and your guests toasty warm in cooler evenings and temperatures, you can follow this proven guide:

Calculate the Size of Patio Heater Needed

Step 1:
Measure the area of the patio that you want to be heated. Remember, you don’t need to heat the entire patio, but only the areas where people are seated or where most people meet. Measure the length, width and estimate a height of say 6 or 8 ft. Multiply the length, width, and height of your area you wish to heat to calculate the cubic feet of that specific zone.

Step 2:
Estimate the average temperate range that you’d like to increase that area by, for example, the air temperature drops from 70 degrees Fahrenheit to 50 degrees Fahrenheit, and you’d like the area heated to 70 degrees. Your temperate range increase will be 20 degrees Fahrenheit.

Step 3:
You will then need to calculate the BTU needed to heat that area to your temperature. To do that, take the cubic feet measurement in the first step, multiply it by 0.133 and multiply that by the temperature increase you estimated in step 2. The result will be the BTU needed for example 40,000.


Learning about the different types of patio heaters, how they emit heat, and the best way to calculate how many patio heaters you need to heat an area will make for better-informed decisions when shopping for patio heaters. Remember that it isn’t always the best method to buy and use the heater with the highest BTU rating, but rather to use a patio heater that is perfectly suited to warming a certain area as efficiently and effectly as possible.