Exact matches only
Search in title
Search in content
Search in excerpt
Search in comments
Filter by Custom Post Type
Back to Garage Heater Comparison Last update:

Garage Heater Sizing - Power/Size Ratio Calculator

Determining the right size garage heater is important because the right size saves money. If the heater is too little, it will burn out and need replacement before the cold season ends and there will be a higher cost of operation since it will be continuously running. If it's too big, the expense will be more than necessary.

Mr. Heater 40, 000 BTU Propane Garage Heaters

There is a simple way to decide the thermal output our garage heaters requires to perform well. We can measure the width and length of our garage and multiply these two numbers. If the garage is 30 feet wide by 30 feet long, the squared footage is 600 feet. With this figure, we can search the Internet for models that offer a garage heater to accommodate 600 square feet. Many brands will list the heating areas their models cover.

There are simple calculations we can follow to make sure we are purchasing the right garage heater for our garage. First, we need to measure the square footage of garage floor by multiplying the length by the width of the interior. For instance, a 20 x 24-foot measurement would be calculated by square footage: 20 x 24 equals 480 square feet.

Second, we multiply square footage by a height of ceiling telling us total cubic footage of heated space requirements. An average ceiling height is eight feet with a square footage of 480 so figure 8 x 460 equals 3840 cubic feet.

Third, the lowest winter temperature is subtracted from the temperature we want to maintain in the garage for the winter. This determines the garage heaters temperature need to rise or generate. In other words, if the low temperature is 47 degrees F, and we wish to sustain a temperature in the garage of 68, we need to calculate the difference between 68 degrees and 47 degrees which is 21.

Four is figuring the number of BTU's need to raise the inside temperature of the garage to where we want it. We will determine the garage's insulation to arrive at the last variable of the equation: total cubic feet times insulation quality times desired rise in heat/means 1.6 BUT's needed, means or stands for the division operator. For this formula, 5 means no insulation, 1.5 little insulation, 1 average and 0.5 excellent. If we use to average the formula would be 1 s 3840 times 21 / 1.6 equals 50,400 BTU's.

Five is adding 10% to requirements of BUT's to keep a safety margin for extremely frigid temperatures. This addition yields BTU requirement of a minimum 55,440.

Additional Considerations

Dyna-Glo 5000W Electric Garage HeaterFor the 600 square foot garage that we mentioned above, we want garage heaters that are able to handle an area slightly larger than our garage’s actual size, perhaps around 700 square feet. Should there be a very cold day, this additional coverage adds extra protection. Also, we should consider insulation. If our garage doesn't have adequate insulation, we will want to consider a unit capable of covering a larger area to make up for the heat loss because of less or no insulation.

The temperature in a garage is altered by many factors including leaving a car or cars outside for a long time in freezing weather and then bringing them into the garage. This will indeed affect the temperature in the garage. Even opening the garage door as a significant effect, dropping the inside temperature in a garage rapidly. If we want the temperature to recover quickly, buying larger garage heaters is probably the way to go. The difference in cost for a bigger unit is usually minimal.

We also need to make sure that the garage heaters we are purchasing are cUL (safety standards of the Canadian Electrical Code) and UL (safety standard established by Underwriters Laboratories (UL)) and approved by the Occupational Safety and Health Administration (OSHA) approved and listed with ETL (safety standard established by Underwriters Laboratories).

Having these certifications guarantees that the heater conforms to the set of nationally recognized safety standards in order to protect consumers and homes.

Websites To Help Determine Garage Heater Size

There are several useful websites that help us decide what size heater we need for our garage.

Ultimate Garage Heaters ( has calculations for hot water, natural gas, electric and infrared garage heater. The site asks us to state the type of energy or fuel source we want information on. Once selected, we are guided through the specifications and recommendations for the size of our garage.

Best Garage Heaters ( detailed information on how to determine what size garage heater we need, along with tips on how to efficiently heat our garage.

Doityourself ( offers information on what size garage heater will heat our garage, as well as ways to determine what it will cost to heat our garage.

Newair ( gives information on garage heater sizes by using a basic rule using watts and space square footage. It takes into account special considerations and suggests a final formulation to determine an adequate size for a heater to adequately heat the squared footage we wish to cover. isn't only about garage doors. This site tells us how to take measurements and gives details on what a space heater will service per square feet insulated or not insulated. It also gives recommendations on different types and brands of garage heaters.

Disclosure: Some of the links in this post are 'affiliate links.' This means if you click on the link and purchase the item, I will receive an affiliate commission.
1 Stern2 Sterne3 Sterne4 Sterne5 Sterne (1,396 Ratings. Average: 4.70 von 5)