What Size AC Unit Do I Need?
Selecting the right-sized AC unit for your home makes a big difference in how comfortable your home is when the summer heat is in full effect. Many homeowners are surprised to learn that there are several other factors that impact your air conditioning needs beyond your home’s square footage.
First, let’s look quickly in more detail at why deciding on the perfect-size AC matters.
Why Choosing the Right AC Matters
No matter which type of AC unit you choose for your home, getting the right size is essential to getting the most out of your air conditioning without wasting energy. AC units are anything but one-size-fits-all.
Issues with an Oversized AC Unit
An oversized AC unit:
- Can cause cold spots throughout the home.
- May not dehumidify your home’s air effectively. This is the result of the AC unit cooling your home quickly and not running long enough to affect humidity levels.
- Can experience frequent short cycles that can decrease the lifespan of your unit, require more AC maintenance, and result in a less comfortable environment for your family.
Issues with an Undersized AC Unit
An undersized AC unit:
- May cause hot spots throughout your home because they are too weak to effectively cool every room.
- May dehumidify your home too effectively by running for long periods to gradually lower temperatures by removing more humidity than necessary.
- May raise your energy bills due to the long running cycles needed to lower indoor temperatures to the desired setting.
- Can reduce the lifespan of your AC unit and cause more breakdowns and service calls.
Finding the Right AC Size for Your Home: Things to Consider
In most cases, homeowners should work with a trusted HVAC professional like One Hour Heating & Air Conditioning to find the right-size AC unit for their square footage. There’s more to selecting the right AC than knowing how big your home is.
Some important variables in AC unit selection include:
- How much direct sun your home receives
- Your number of windows and their energy efficiency
- The efficiency of your air ventilation
- The quality of your insulation
- Home heating elements like fireplaces or wood stoves, that influence heating or cooling loss
Several of these factors are considered by HVAC technicians when they use something called the Manual J calculation to help them decide the best-sized air conditioner for a homeowner.
The Manual J Calculation
The Manual J calculation is used by HVAC technicians to identify the heating and air conditioning needs of a home or commercial building. Like any formula, the key to this calculation is working with accurate information. HVAC technicians take precise measurements throughout the home, often conducting tests to assess the efficiency of insulation or the quality of seals on doors and windows.
The basic elements of the calculation include:
- Square footage of the home or facility
- An evaluation and rating of the insulation
- The number of occupants
With this information, HVAC technicians can attribute a set number of BTUs (British Thermal Units). BTUs measure how much heat will raise the temperature of water. In this case, it’s a way of accounting for heat sources like people, windows, and doors.
Calculating the AC Unit Load
The AC load is the total amount of output required to cool a home. The calculation looks like this:
- (square footage) x (ceiling height) x 20 BTUs
- (number of occupants) x 100 BTU
- (number of entry doors) x 1,000 BTU
- (number of windows) x 1,000 BTU
By adding the total number of BTUs from all of these equations, your technician will have the total AC unit load required for your home and be able to recommend the right-sized AC unit.
How Are AC Units Measured?
AC units are measured in tons. Small residential air conditioning systems are 1 to 1.5 tons. AC unit sizes increase by half-ton increments while the largest residential units are 5 tons. Homes larger than 4,000 square feet may have to look at custom HVAC solutions to meet the needs of that much space.
Find the Right AC Unit for Your Home: Call Today
At One Hour Heating & Air Conditioning, we take the time to measure, test, and calculate your AC unit needs to keep your home comfortable. With expert HVAC technicians and decades of experience with air conditioner installation and other cooling services, we’re ready to help you enjoy summer like never before. Call (800) 893-3523 or request an estimate today.