How to Determine the Size of the HVAC You Need

One of the most important things that affect the efficiency of an HVAC system is its size. If your HVAC is too small for your home, it will work too hard trying to heat and cool properly, but to no avail.

An oversized HVAC system, on the other hand, will cool or heat your home faster; however, it won’t run long enough for the dehumidification process to take place. Plus, you will have inconsistent heating or cooling throughout your home.

We cannot emphasize enough the importance of choosing the appropriately-sized HVAC system. It will operate efficiently, save you money, and help maintain a comfortable temperature year-round.

Here is an easy to follow step-by-step guide to determine the approximate size of your HVAC.

  • Calculate the Square Footage of Your Home: If you do not know the total square footage of your home, you will have to measure every room. Draw a rough sketch of your home. Label all of the rooms you need to measure including hallways. Measure the length and width of every room. To get the total square footage of a room, multiply its length by its width. For instance, if a room is 12 feet by 20 feet, its total square footage is 12*20 =240 sq. ft. Add the square footage of each room to find the total for your home.
  • Determine the Base BTU: The British Thermal Unit (or BTU) is a unit of heat. To determine the base BTU for HVAC sizing, multiply your home’s total square footage by 25 (the approximate amount of energy required to cool a square foot of an average-sized home). If your home’s total square footage is 1,000 sq. ft., the BTUs you need are 1000*25= 25,000 BTUs
  • Account for High Ceilings: If your ceiling is over eight feet, multiply the base BTU by 1.25

Once you calculate the base BTUs for your home size, you can determine the size of cooling and heating units you need. To determine AC tonnage, divide your base BTU by 12,000. So, if your base BTU is 25,000 BTUs, you need (25,000/12), which comes to about two tons.

A furnace with an 80 percent efficiency would need a BTU output of around 25,000*0.8 = 20,000 BTU.

These are basic calculations. When sizing your HVAC, there are several factors to take into account, including the number of people in the building, the number and placement of windows, and the amount and type of insulation.

South Placer Heating and Air is a reputable air conditioning company in Roseville. We take the guesswork out of sizing HVAC units. We will use the Manual J Calculations to accurately estimate the size of HVAC you need. To consult one of our professionals, call (916) 246-2089.