Your air conditioner should be the right size for your home. If it’s too big or too small, it will not provide the comfort you are wanting for your home. Fortunately, identifying what you need for your home is not a matter of guessing, but simple math.
Why People Think Bigger Is Better
Many people simply think a bigger system will either make their home cooler or will cool their home more quickly. This makes sense given the size of the system is measured in how much it can cool in an hour. However, this shows a little misunderstanding of how air conditioners work.
When your air conditioning is running, it not only produces cold air but also acts as a dehumidifier. Removing moisture from the air with your air conditioner takes a little time. When your system is oversized, it will not run long enough cycles to lower the humidity.
Oversized systems also pose problems with the function of the system. If the system is too large, it actually causes the system to run shorter cycles more often. This is extremely hard on the components, reducing their expected service life.
It also drives up your utility costs because you are running a larger system. This means that when your system is too big, you end up paying a lot more and not being as comfortable.
How Is Air Conditioner Size Measured?
Air conditioner size is not measured in terms of inches, but BTUs. This stands for British thermal unit and is a measure of the energy required to raise 1 pound of water by 1 degree Fahrenheit.
For air conditioning, the BTU rating is an indication of how much cooling the system can provide in one hour. The greater the BTU rating, the more cooling it can provide, but it uses more energy to achieve that desired cooling.
Start With Your Home Size
The best way to determine how much cooling capacity your air conditioner need is to start with the home’s size. This is generally measured in square feet, which is relatively easy to calculate. The geometrical formula is simply to multiply the width by the length of your space to get square feet.
However, most of our homes are not perfect squares or rectangles, which makes it a little more tricky. Start by determining which areas of your house are serviced by the air conditioner. These areas are going to have vents or registers and will be on the same level as other areas serviced.
Note that even if you shut off your vents in a room, the air conditioner will still work to cool those spaces. This is because the air still circulates through those rooms, so the temperate is raised. Closing your vents actually causes the air conditioner to work harder and increases the pressure in your ductwork.
Be sure to consider your attic, garage, and basement as well. If there is a vent in the space, you need to include that in the calculation.
Multiply to Get BTUs
The next step is to determine how many BTUs are needed to cool that space. While there is no specific formula for this, the general rule of thumb is 20 BTUs per square foot you are cooling.
So, if your home is 1,500 square feet, you’ll need an air conditioner with 30,000 BTUs. This is the starting point, but your specific need may be adjusted up or down depending on several factors.
Consider Other Factors
Your environment will influence how many BTUs you need for your air conditioner. For instance, if your home is mostly shaded throughout the day, you can probably reduce your need for BTUs by about 10%. However, if you have no shade covering your home, you may need to increase it by about 10%.
Likewise, the number of people in your home during the heat of the day will influence how many BTUs you need. The 20 BTU rule of thumb accounts for about two occupants. For every additional occupant, you will need to increase your estimate by about 600 BTUs per person.
Remember that this calculation is just an estimate to roughly determine the size of unit you will need. The best way to ensure you have the right size is to work with a trusted and experienced air conditioning professional.
People around Wheat Ridge have turned to Coffman & Company for our air conditioning expertise for over 35 years. Our customers also trust us for heating services, cooling services, and water heater maintenance and repair.