A Comprehensive Guide to Terrace Heaters and Their BTU Output

Terrace heaters, also known as outdoor heaters or patio heaters, are a popular choice for extending the use of outdoor spaces during colder months. These heaters work by radiating heat from a fuel source, such as propane or natural gas, and are commonly used in residential and commercial settings. One of the most important factors to consider when selecting a terrace heater is the BTU output, which determines the amount of heat generated and the heater's efficiency.

What is BTU?

BTU stands for British Thermal Unit, which is a unit of energy commonly used to measure heat. One BTU is defined as the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit. In the context of terrace heaters, BTU output refers to the amount of heat generated by the heater over a specific period, typically measured in BTUs per hour (BTU/hr).

Factors that Affect Required BTU Output

The required BTU output for a terrace heater will depend on several factors, including:

Outdoor Space Size: The larger the outdoor space, the higher the BTU output required. As a rough estimate, you should aim for a minimum of 10,000 BTUs per hour for every 100 square feet of outdoor space. For example, if you have a 500 square foot patio, you would need a heater with a minimum output of 50,000 BTUs per hour.

Ambient Temperature: The colder the ambient temperature, the higher the BTU output required to achieve a comfortable temperature. For example, a heater with a 40,000 BTU output may be sufficient to heat a patio to a comfortable temperature on a mild fall evening but may not be sufficient on a freezing winter night.

Desired Temperature Increase: The greater the desired temperature increase, the higher the BTU output required. For example, if you want to raise the temperature of your patio by 20 degrees Fahrenheit, you will need a higher BTU output than if you only want to raise it by 10 degrees Fahrenheit.

Heater Efficiency: The efficiency of the heater will affect the amount of heat generated for each unit of fuel consumed. Higher efficiency heaters will require a lower BTU output to achieve the same level of heat as lower efficiency heaters.

Types of Terrace Heaters

There are several types of terrace heaters available on the market, each with its own unique advantages and disadvantages. The most common types of terrace heaters are:

Propane Heaters: Propane heaters use propane gas as a fuel source and are available in both freestanding and tabletop models. Propane heaters are easy to use and offer a high degree of mobility since they do not require a natural gas line. However, propane heaters require propane tanks, which need to be refilled or replaced periodically, and may be less cost-effective in the long run than natural gas heaters.

Natural Gas Heaters: Natural gas heaters use natural gas as a fuel source and are typically mounted to a permanent gas line. Natural gas heaters are more cost-effective than propane heaters in the long run and require less maintenance since they do not require propane tank refills. However, natural gas heaters may be less mobile than propane heaters, and installation costs may be higher since a gas line needs to be installed.

Electric Heaters: Electric heaters use electricity as a power source and are available in both freestanding and wall-mounted models. Electric heaters are easy to use and do not require any fuel or gas lines. However, electric heaters may be less cost-effective in the long run than gas heaters since they consume a higher amount of energy to generate the same amount of heat.

Infrared Heaters: Infrared heaters use infrared radiation to heat objects directly, rather than heating the air around them. Infrared heaters are available in both electric and gas-powered models and are highly efficient, requiring less energy to generate the same amount of heat as traditional heaters. Infrared heaters are also less affected by wind and can be more effective in outdoor settings than other types of heaters.

Normal BTU Output for Terrace Heaters

The normal BTU output for terrace heaters can vary greatly depending on the type and model. Residential terrace heaters typically have a BTU output ranging from 30,000 to 50,000 BTUs per hour. Commercial-grade heaters may have a much higher output, up to 200,000 BTUs per hour or more.

Propane heaters typically have a BTU output ranging from 30,000 to 50,000 BTUs per hour, while natural gas heaters can have a higher BTU output of up to 75,000 BTUs per hour. Electric heaters typically have a lower BTU output, ranging from 5,000 to 10,000 BTUs per hour, while infrared heaters can have a BTU output ranging from 9,000 to 40,000 BTUs per hour.

Choosing the Right BTU Output

Choosing the right BTU output for your terrace heater is essential to ensure that you can comfortably use your outdoor space during colder months. As mentioned earlier, the required BTU output will depend on several factors, including the size of your outdoor space, the ambient temperature, the desired temperature increase, and the heater's efficiency.

To determine the required BTU output for your terrace heater, you can use the following formula:

BTU/hr = Area of outdoor space (in square feet) x Temperature increase (in degrees Fahrenheit) x 10

For example, if you have a 500 square foot patio and want to raise the temperature by 20 degrees Fahrenheit, the required BTU output would be:

BTU/hr = 500 x 20 x 10 = 100,000 BTUs per hour

It's also important to consider the heater's efficiency when selecting the BTU output. Higher efficiency heaters will require a lower BTU output to achieve the same level of heat as lower efficiency heaters. Look for heaters with a high AFUE (Annual Fuel Utilization Efficiency) rating, which indicates the percentage of fuel that is converted into usable heat.

Final Thoughts

Terrace heaters can be a great addition to any outdoor space, allowing you to enjoy your patio or deck even when the temperature drops. When selecting a terrace heater, it's important to consider the BTU output to ensure that you can generate enough heat to keep your outdoor space comfortable. By considering the factors that affect required BTU output, choosing the right type of heater, and selecting a heater with a high efficiency rating, you can enjoy your outdoor space year-round.

Recource links 

1. "What is a BTU?" by Energy.gov: https://www.energy.gov/energysaver/home-energy-audits/sizing-heating-and-cooling-systems/what-btu
2. "How to Calculate the BTUs for Your Room" by The Spruce: https://www.thespruce.com/how-to-calculate-btu-for-your-room-1152765
3. "What is a BTU and How Many Do You Need?" by AC Direct: https://www.acdirect.com/what-is-a-btu
4. "Understanding BTUs and Air Conditioning Efficiency" by Energy Star: https://www.energystar.gov/products/heating_cooling/air_conditioning_central/understanding_btu_and_eer
5. "What is a BTU and How Do You Choose the Right Fireplace?" by Heat & Glo: https://www.heatnglo.com/shopping-tools/blog/what-btu-and-how-do-you-choose-right-fireplace