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The best way to save money on a NewAir Garage Heater is to buy one the right size for the space you want to heat. Too small, and it will run up your power bill trying to heat a space beyond its capacity. Too big, and you’ll waste money on heating power you can’t use. Garage heaters also become physically larger as they increase in size, and a large heater in a small space is cumbersome and difficult to mount. Fortunately, estimating the right size garage heater that you need is easy with a few simple measurements and a bit of math.

How to Estimate Garage Heater Size

There are two ways to estimate the size of your garage heater. The simplest way is to follow the rule of 10 watts per square foot of floor space. A 22 ft. x 24 ft. garage has 528 square feet, so the easiest way to estimate the required wattage is to multiply by ten. 528 x 10 = 5230 watts, so a unit like the NewAir G56 Electric Garage Heater (5600 watts) would be more than enough to keep it warm. Since electric garage heaters are rated according to their wattage and gas garage heaters are rates according to BTUs, you can estimate the required size of a gas heater by multiplying by the wattage by 3.41. 5280 x 3.41 = 18,005 BTUs.

(Insulation * Volume * Temperature Rise)/1.6 = BTU

The other way is to estimate the size of your garage heater is to calculate the number of BTUs or watts required to match the desired temperature rise in your garage. It’s a more complicated, but more precise method. Start by determining your desired temperature rise, then measure the volume of the space you want to heat. A 22 ft. x 24 ft. garage with 8 foot ceilings has a total of 4224 cubic feet of air (22 x 24 x 8 = 4224). Next, estimate the degree of insulation in your garage. The recommended degree of insulation, what’s considered average for a home, varies considerably from region to region. Walls in rooms in extremely cold climates require an R-value of 25-30, while walls in rooms in extremely warm climates only require an R-value of 13-15. Check the recommended R-value of your region by clicking here. The degree of insulation should be rated based on how far above or below it is from the recommended average. Use a rating of 5 if your space has no insulation, 1.5 if it has weak insulation, 1 if it has average insulation, and 0.5 if it has strong insulation. Once you’ve assembled all your figures, you can calculate the number of BTUs required by plugging them into this formula:

How to Size a Garage Heater

The formula for our hypothetical 22 x 24 garage (Average insulation, 4224 sq. ft., and a 25°F desired temperature rise) would be:

(1 * 4224 * 25)/1.6 = 66,000 BTU

To convert that into watts, divide by 3.41.

66,000/3.41 = 19,354 Watts

Since it is unlikely we could find an electric garage heater rated for 19,354 watts, you would either need to install a gas heater or multiple electric heaters to heat the space to your desired temperature. The only other option would be to increase the degree of insulation and therefore reduce the amount of energy required to heat it. For example, if you doubled the insulation in our 22 x 24 garage, you’d only need a garage heater half the size as before.

(0.5 * 4224 * 25)/1.6 = 33,000 BTU

33,000 BTU/3.41 = 9677 Watts

If you’re not certain how to improve the insulation in your garage, read How to Reduce the Energy Costs of Your Garage Heater to see some simple tips on how to increase its R-value.

Garage Heater Size Calculator

Fill in the inputs section to find out what size space heater you need. If you don't know what climate you live in, see the section 4, the climate zone section above.

Heater Types

There are two types of garage heaters: gas heaters and electric heaters. NewAir garage heaters are all electric and operate according to the principle of Joule heatin n, also known as resistance heating. Electricity is passed through a metal conductor, where it’s transformed into heat and released into the surrounding air. The amount of heat generated is proportional to the square of the current multiplied by the electrical resistance of the metal. NewAir electric garage heaters are radiant heaters. Though they’re assisted by a fan, they warm primarily through the emission of infrared rays, which are absorbed directly by you and the objects in your garage, making them extremely useful in spaces with poor insulation. 

Benefits of Electric Garage Heaters

- 100% Efficient

- Fast Heating of Enclosed Spaces

- Simple Thermostat Control

- Reliable

- No Waste Fumes

- Compact

- No Open Flame

- Lightweight

In a gas heater, propane or natural gas is fed through a gas valve inside the heater and ignited by a sparker or pilot flame. The burning fuel warms a heat exchanger, which activates a fan that blows air through it and out into your garage. The heat from the exchanger warms the air as it passes through, and transfers it to you. Some heaters use a low-intensity infrared tube instead of a fan. The tube absorbs heat and emits infrared rays, similar fashion to a NewAir electric garage heaters.

Benefits of Propane and Natural Gas Heaters

- Powerful

- Natural Gas Heaters Don’t Need

- Adjustable Louvers to Direct Heat

- Fast Heating

- Large Size Selection

- Large Coverage Area

- Durable

- Cheaper to Operate

Gas heaters have one major advantage and several disadvantages compared to electric heaters. On the one hand, they’re far more powerful than electric heaters and often the only feasible way to heat large garages in exceptionally cold climates. On the other hand, they’re not as efficient as NewAir electric garage heaters, where 100 percent of the electricity used is emitted as heat. Gas heaters burn off some of their fuel as waste fumes like carbon monoxide. Up to 20 percent of the gas is burned off, depending on the model, and has to be vented in order for the heaters to be used safely indoors. Ventilation equipment may not only be time consuming and expensive to install, but it also robs some of the warmth from the heat exchange. It’s pulled up through the vent along with the waste fumes.

Additional Considerations

Determining the correct garage heater size is not the only consideration that needs to be taken into account when making a purchase. You should also pay attention to whether the unit you’re purchasing is UL approved, cUL approved, or ETL listed. These certifications ensure the unit conforms to the nationally recognized set of safety standards put in place to protect homes and consumers.

UL Certification

UL refers to the set of safety standard established by Underwriters Laboratories (UL) and approved by the Occupational Safety and Health Administration (OSHA) to assess the safety features of Transient Voltage Surge Suppressors (TVSS) and Surge Protection Devices (SPD). Compliance to UL safety standards has been made mandatory by the National Electrical Code (NEC), the regional standard for the safe installation of electrical wiring and equipment in the United States. Appliances with the UL sticker have had product samples checked by UL technicians, certifying that they are in compliance with the laboratory’s safety requirements. All NewAir garage heaters are UL certified.

cUL Certification

cUL refers to the safety standards of the Canadian Electrical Code, issued by the Canadian Standards Association. Though cUL standards are similar to UL standards, the two are not interchangeable. All NewAir garage heaters are cUL certified.

ETL Certification

Products that contain the ETL mark have been certified by the Edison Testing Laboratories (ETL) and conform to their safety standards. Like the UL, ETL is a Nationally Recognized Testing Laboratory (NRTL) and part of OSHA. They provide independent verification that an electrical product conforms to appropriate standards for home use. Standards set down by UL and ETL are very similar, and any product certified by either laboratory has been demonstrated it is safe for use in North America. The NewAir G56 Electric Garage Heater is ETL certified.


In order to determine the correct heating capacity you require, there are a few terms that are beneficial to know.

Wattage (Watts)

A unit of power equivalent to one joule of energy per second. Watts measure the rate of energy conversion or transfer over time and is determined by multiplying amperage (the amount of electricity used by a machine) by voltage (the electric pressure required to move a charge between two points). NewAir heaters carry 120 volts of current and are rated up to 5600 watts. The general guideline when sizing heaters is 10 watts for every square foot of space. For example, the NewAir G56 Electric Garage Heater has a wattage of 5600 watts, which means it can easily and effectively heat an area of up to 560 square feet.

BTU (British Thermal Unit)

A British Thermal Unit is the amount of energy required to heat one pound of water by one degree, roughly 1055 joules, or roughly the amount of energy required to completely burn a four-inch wooden match. One watt equivalent to approximately 3.41 BTU.

Temperature Rise

The amount of heat required to raise the internal temperature of a structure to your desired level. Subtract the temperature outside from your desired temperature outside to calculate temperature rise. For example, if the average temperature outside your garage was 40°F, and you wanted to heat your garage to 65°F, the formula would be 65°- 40° = 25°F, the desired temperature rise.


R-value measures thermal resistance, how well a material resists heat flow. The higher a material’s R-value, the more effective it is as an insulator. Fiberglass insulation, the most common insulator used in residential buildings, has an R-value of 2.9-3.8. R-value is important when calculating heater size because it determines the degree of heat loss and the size of heater needed to maintain a comfortable temperature in your garage.

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