How to Determine the Amount of Residential HVAC Per Square Foot

Properly sized heating and cooling units will make your home comfortable all year round. Unfortunately, many homes have air conditioners and heaters that are too large or too small for their space. An air conditioner that is too large will cycle for short periods of time and not remove the humidity in the air, while a small unit won’t cool down your home properly. A large heater will short cycle, turning off frequently, and an undersized unit won’t heat your home fully.

Measuring tape

Instructions

- 1
  Measure the all the rooms in your home that the HVAC unit needs to heat and cool. Be sure to measure the hallways and bathrooms as well.
- 2
  Calculate the square footage of each room in your home. Multiply each room’s individual length by the width to find out the square footage of the room. For example, a room that’s 10 feet by 15 feet would have a square footage of 150 square feet.
- 3
  Add the square footages of each room in your house together for the total square footage.
- 4
  Determine how big your air conditioning unit should be based on the square footage. For every 450 to 500 square feet of space, you need 1 ton of cooling to keep your house comfortable.
- 5
  Determine the size of your heater. Multiply the number of square foot by the number of British thermal units needed to heat that area. In warm climates, you’ll only need 20 to 25 BTUs. In mild climates, you’ll need 30 to 40 BTUs. In cool to cold climates, you’ll need between 40 to 50 BTUs for proper heating.

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