The adage that bigger is always better doesn’t apply when selecting an AC unit for your home. Your AC unit will function best and most efficiently when it’s properly sized for your home.
Factors Influencing AC Unit Size
Many factors should be considered when buying a new AC unit, including:
- Square footage and ceiling height
- Number of doors and windows (heat gain or loss)
- Number of occupants
- Manual J calculation result
A Manual J calculation will yield the most accurate result for the size unit you need. A simple formula is to determine the square footage of your home and multiply it by 25, which will yield the number of BTUs you’ll need.
Generally, you’ll need one ton for every 500 square feet you need to cool.
Buying a larger unit won’t help if your AC unit is in direct sunlight for at least a few hours daily, although your monthly energy consumption can increase by more than 10 percent, according to the U.S. Department of Energy.
If this applies to you, consider providing a cover to shade your unit or installing the unit in a different location.
Additional factors influencing the size AC unit you need include:
- Geographic location
- Quality of your ductwork
- Home construction materials
- Number of heat-generating appliances typically used
- Weatherproofing condition of the house
- Home features, such as sunroom, fireplace, and so forth
- Whether you need an AC unit or an HVAC unit
- Whether the unit is electric or gas
How Are AC Units Sized?
AC units are sized according to BTUs, which stands for British Thermal Units. That number indicates the energy required to remove heat from the room in an hour. Specifically, and according to the EIA, a BTU is the amount of energy required to raise the temperature of 16 ounces of 39° F water by 1° Fahrenheit (F).
If your AC unit is larger or smaller than you need, it will run less efficiently and increase your energy consumption. A larger unit will not cool the room more quickly. It will, in fact, take longer to cool because it’s running less efficiently. You may also experience increased humidity with an oversized unit. You can remedy the humidity issue by purchasing a dehumidifier, but that will increase your energy consumption. A unit that’s too large may cycle continuously throughout the day and wear out more quickly.
If the unit is too small, you’ll likely experience uneven and inadequate cooling. The unit may ice up and stop working.
The 20-Degree Rule
Experts agree that your AC unit should not be set at a temperature that’s more than 20 degrees lower than the outside temperature.
If you live in a very hot climate, this can be an issue, but buying a larger unit won’t help. If it’s more than 100 degrees outside, leave your unit set at 78 degrees for maximum efficiency, but don’t just buy a larger unit in the hopes that it will compensate for the heat. AC units can be single-stage or two-stage, so if you live in an area that has temperature extremes, you might need a two-stage unit.
Need A New AC Unit?
If your AC unit isn’t cooling as well as you’d like, or not at all, then contact One Hour Service Minds Air Conditioning & Heating for all your AC installation and repair needs in Melbourne, FL. We’ve been servicing our Melbourne neighbors since 1996 and we’re sure you’ll be happy with our service.
We vet and background-check all our service techs so you can feel comfortable allowing them into your home. We’re among the best in the area, so give us a call if you need a new AC unit or if you need maintenance or repair.