How to Select The Right Size Air Conditioning System

Jan 20th, 2016 | News

How to choose the right size Air Conditioning systemOne thing that is very important for a homeowner to know is how powerful an air conditioning unit needs to be in order to cool down their home in the most efficient and cost effective way. Obviously, an air conditioning unit that is too small won’t heat the house sufficiently and may burn itself out trying to. A unit that is too powerful wastes energy and money. An air conditioner not only cools a space but lowers humidity. An overly powerful air conditioner does not take humidity out of the air effectively because it cycles on and off. Because of this, the homeowner is left with rooms that feel cold and clammy. How does a person know how to choose the right size Air Conditioning system?


Energy yields are reckoned in British thermal units, or Btus. A Btu is how much heat it takes to raise a pound of water one degree Fahrenheit. An air conditioner is sized by the Btus it can delver in an hour, or a Btuh. Ton describes the output from the air conditioner. One ton of cooling output equals 12,000 Btu.

A units SEER rating also helps a customer choose the right A/C system. The SEER, or Seasonal Energy Efficiency Ratio is the cooling output divided by the total electrical energy input over a season. Carrier Air conditioners sell units that range from 15 to 21 SEER.

About Air Conditioning Units

First, our technicians as Bradley Heating and Air Conditioning will assess a customer’s house to determine the Btuh coming into the house from sources other than the HVAC system. Heat comes first from the sun, then the roof, overhangs, windows, doors and exterior walls. The technician will also find the hot and cold spots inside the house and ascertain how many appliances there are, as these also give off heat. He or she will also need to know how many people live in the house in order to choose the right A/C system. This may be done for room air conditioning or central air conditioning.

With central air conditioning, once the heat gains are determined, our installer will check the house’s furnace blower, ductwork and plenum to see if they can handle the load of cooled air. If they can’t, some of these parts may need to be replaced or modified. The homeowner may want a zoned air conditioning system, to mention one instance. With a zoned system, the system cools only one or two rooms that are occupied while unoccupied rooms in the house are not cooled. This saves money.

According to Energy Star, a room that’s 100 to 150 square feet needs an air conditioner that yields 5,000 Btuh. From 400 to 450 square feet needs 10,000 btuh, while 700 to 1,000 square feet need 18,000 Btuh, or an air conditioner that delivers ton and a half to be cooled efficiently. A 2,000 to 2,500 square foot room needs 34,000 Btuh, which needs an air conditioner that delivers a bit less than three tons. Four thousand Btuhs should be added to these totals if the area to be cooled is a kitchen.

The Btuh can be reduced by about 10 percent if the room is in heavy shade, while the Btuh in a room that gets floods of sunlight should be raised by the same amount. If there are more than two people who are often in the same room, like a bedroom, 600 Btuhs should be added to the capacity.

The homeowner might also want a multi-speed condensing system, which tailors the energy output of the condensing unit to the needs of the house. Thermostats can also be installed that let the homeowner know if the system is operating on low or high speed. They can also be programmed to turn off and on automatically on a schedule. Some newer thermostats can even be operated remotely, through the homeowner’s I-phone.