What size Infrared Heater do I need? 

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infrared heater size

When choosing an infrared heating system for your garage, patio, or indoor space, there are various factors you need to consider. For instance, you’ve to look for a product from a reputable brand and style that matches your interiors. More importantly, you’ve to ask yourself; what size infrared heater do I need? 

Since infrared heaters are available in different sizes, you might end up with a unit that is either too big or too small. If the heating system is too small, you will not get enough heat to keep your space warm. And if it’s too big, you’ll be wasting energy and overheating the space. 

Therefore, it’s important to find the right infrared heater size if you want to keep your space comfortable, without running up huge energy bills. Hopefully, this guide will help you select the right heater size that will meet your space heating needs! 

Infrared Heater Wattage 

A wattage is a unit of measure that shows the maximum power output of a heater. Interestingly, the total recommended wattage of an infrared heater is usually lower than that of other heating solutions like storage heaters and radiators. This shows that infrared heaters have better energy efficiency than conventional heating systems. 

The first step to ensuring that your room is heated effectively is choosing an infrared heating system that meets your required wattage. However, if you’ve to choose between a heating system of a lower or higher wattage than your recommended total, always select higher. Choosing a lower wattage heater will force it to work harder to heat your space, thus shortening its lifespan and reducing its efficiency. On the contrary, powerful heaters heat the space with ease, and you can even fit them with a thermostat. That way, the thermostats will automatically switch off the heater when the room reaches the desired temperature, giving you comfortable heat at optimum efficiency. 

In addition to choosing the right infrared heater wattage for your system, make sure you position the units in a way that heats every part of the room. This is because infrared heaters heat directly, so they’ll not heat parts that are out of their heating span. Combining small heaters offer a better heat distribution as opposed to one large IR heater! 

Infrared Heater BTUs 

BTUs is an acronym for British Thermal Units per hour. It represents the amount of heat needed to increase 1 pound of water by 1 deg F.

Unlike electric models, gas-powered infrared heaters are rated according to their BTU output. In general, the higher the BTU output of a certain heater, the larger the space it will heat. Also, higher-rated BTU heating units are more costly to buy and operate as they require more energy. Therefore, it’s important to determine your heating requirements as accurately as possible to reduce your expenses. 

How to estimate the infrared size for your space 

There are 2 ways to estimate the ideal infrared heater size that will meet your heating needs. 

  • Assume that 10 watts will be sufficient to heat 1 sq ft of floor space. 

For instance, if you want to heat a 22 X 24 ft garage, you need to calculate its floor area first, which will be 528 sq ft. Next, multiply the floor area by 10 to get the required wattage. That is 528 X 10 = 5230 W. Therefore, an electric infrared heater with a wattage of about 5600W will provide sufficient heat to keep your garage warm. 

However, if you want to heat the space with a gas-powered heater, you can multiply the wattage by 3.41 to estimate the heater size in BTUs. In this case, 5280 W X 3.41 = 18,000 BTUs. 

  • Calculate the number of watts/ BTUs needed to match the desired temperature increase in the space you intend to heat. 

Although this technique is more complicated, it’s more precise than the above method. 

First, determine the temperature increase and measure the volume of the room you want to want. To use the example we used earlier, let’s assume that the 22 X 24 ft garage has a height of 8 ft. Therefore, the total volume of the space will be; 22 X 24 X 8 = 4224 Cu. Ft. 

In addition, you need to estimate the level of insulation in the space you want to heat. Walls in houses in warm climates need an insulation level (R-value) of about 13 – 15. While homes in very cold climates need insulation of 25 – 30. The recommended level of insolation varies from one region to another, as demonstrated by this table on Energy Star. 0.5 is used for spaces with strong insulation, 1 for average insulation, 1.5 for weak insulation and 5 for no insulation. 


After getting all the figures we’ve stated above, use the formula below.

BTU = (Insulation X Temperature increase X Volume)/ 1.6. This will help you find the number of BTUs needed to heat a specific space with an IR heater. 

Getting back to our 22 X 24 ft garage with average insulation and the desired temperature increase of 25 deg F, that will be; 4224 X 25 X 1 = 66,000 BTUs. Divide this figure by 3.41 to convert it to watts. That is 66,000/ 3.41 = 19,354W. 

Unfortunately, since most infrared heaters have low wattage, it’s almost impossible to find an electric IR heater with a rating of 19,354 W. Therefore, you’ll either need multiple electric IR heaters or a gas IR heater to heat your space to the desired temperature. Alternatively, you can increase the level of insulation in the space to minimize the amount of energy needed to heat it.

How much space can you heat with a 1500W Infrared Heater? 

As mentioned earlier, manufacturers usually rate electric heaters by the BTUs of heat they put out and watts consumed. The 120V, 1500W unit is one of the most commonly used infrared heaters for heating small spaces. But, exactly how much space can it heat? 

To start, this unit produces about 5,100 BTUs of heat and consumes 1500W of electricity per hour. When determining the size of an electric IR heater, the unit should consume about 10 watts of power to heat a space of 1 sq ft. 

Since 1 W of electricity generates 3.41 BTUs of heat, 10W of power is equivalent to 34 BTUs of heat output per square foot. Therefore, a 1500w IR heater producing 5100 BTUs generates enough heat for a space with a floor area of 150 sq ft. This is equivalent to a 12 X 12.5 FT, 11 X 14 FT, or a 10 X 15 FT room with a standard 8 ft ceiling. 


In addition to checking the heat output of the infrared heater, it’s important to check its physical size. This will help you choose a heater that will fit in your space. For that, you should carefully measure the space you intend to install the heater and confirm the dimensions of each unit. And if the room you intend to heat with the units has limited wall space, consider investing in a ceiling-mounted IR heater. At the same time, consider other factors like the room layout and personal preferences on aesthetics before you settle on a specific heater! 


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