Heater Size Calculator For Garage

Determining the right heater size for your garage is crucial for maintaining a comfortable temperature and preventing damage to your vehicles and belongings. An oversized heater will waste energy and increase your heating costs, while an undersized heater will struggle to keep the space warm. To ensure optimal performance and energy efficiency, it's essential to calculate the required heater size based on your garage's specific dimensions and insulation level.

To calculate the heater size for your garage, follow these steps:

1. Determine the Volume of Your Garage

Begin by calculating the volume of your garage in cubic feet. Multiply the length, width, and height of your garage to obtain the volume. For instance, a garage measuring 20 feet long, 15 feet wide, and 10 feet high has a volume of 20 x 15 x 10 = 3,000 cubic feet.

2. Determine Insulation Level

The insulation level of your garage plays a significant role in heat retention. Well-insulated garages require less heating than poorly insulated garages. The insulation level is typically measured in R-value, which indicates the resistance to heat flow. The higher the R-value, the better the insulation.

If your garage is well-insulated with an R-value of 19 or higher, multiply the volume by 10 BTUs per cubic foot. If your garage is moderately insulated with an R-value between 11 and 18, multiply the volume by 15 BTUs per cubic foot. If your garage is poorly insulated with an R-value of 10 or less, multiply the volume by 20 BTUs per cubic foot.

3. Consider Heat Loss

Heat loss occurs through walls, ceilings, windows, and doors. To account for heat loss, add 1,000 BTUs for every 100 square feet of exterior wall space, 500 BTUs for every 100 square feet of ceiling space, and 250 BTUs for every window and door.

4. Example Calculation

For example, let's calculate the heater size for a garage measuring 20 feet long, 15 feet wide, and 10 feet high with an R-value of 15. The volume of the garage is 3,000 cubic feet.

Moderately insulated: 3,000 cubic feet x 15 BTUs per cubic foot = 45,000 BTUs
Exterior wall space: 20 feet (length) x 15 feet (width) x 2 (sides) = 600 square feet x 1,000 BTUs per 100 square feet = 6,000 BTUs
Ceiling space: 20 feet (length) x 15 feet (width) = 300 square feet x 500 BTUs per 100 square feet = 1,500 BTUs
Heat loss total: 6,000 BTUs (exterior walls) + 1,500 BTUs (ceiling) = 7,500 BTUs
Total required heater size: 45,000 BTUs (insulation) + 7,500 BTUs (heat loss) = 52,500 BTUs

Based on this calculation, a heater with a capacity of approximately 52,500 BTUs would be suitable for this garage.

Note that this calculation provides an estimate of the required heater size. Factors such as the climate, desired temperature, and the presence of additional heat sources can influence the actual heater size needed. It's always advisable to consult with an HVAC professional for a more precise assessment and heater selection.