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What else should I know about air conditioners before I buy one?
Home » HVAC » Air Conditioners » What else should I know about air conditioners before I buy one?In choosing an air conditioner or when considering an upgrade, you must consider the BTU and (S)EER.
¤ BTU (British Thermal Units) ¤
Technically, a BTU is the amount of heat required to raise the temperature of one pound of water by 1ºF, or 0.45 kilograms of water by 0.56ºC. (1 BTU = 1055 Joules)
When an air conditioner refers to a "ton" for BTU, 1 "ton" equals 12,000 BTU.
This is how much energy an air conditioner has. Its energy will determine how much distance it can cool.
A rough estimate of the size needed per room is as follows:
Room Size BTU Needed
100 to 250 sq. ft. 5,000 to 6,600 BTU
250 to 350 sq. ft. 6,600 to 7,700 BTU
350 to 450 sq. ft. 7,700 to 10,000 BTU
450 to 550 sq. ft. 11,000 to 13,500 BTU
550 to 700 sq. ft. 13,500 to 15,000 BTU
If you get a central air conditioning system, you must consider the size of your house to determine the needed BTU.
¤ EER (Energy Efficient Rating) ¤
The higher this number is, the better. You want an air conditioner that rates at least 13; the energy star rating begins at 10.7. (EER = BTU rating ÷ wattage)
In looking at air conditioners, consider the EER the same as the SEER (Seasonal Energy Efficient Rating). They are slightly different in actuality, but they are used interchangeably.
This rating has no bearing on how well a particular air conditioner cools. This rating refers to the amount of energy the air conditioner uses while cooling. Therefore, a high EER will mean a difference in your electricity bill. Even a change of one number higher can bring significant savings.
To determine how much you would save per year with a certain EER rating, multiply the approximate number of hours you will be using the air conditioner times how much a kilowatt-hour (kWh) costs in your area.
From EER:
# hours operated X cost per kWh = savings per year
From SEER:
unit capacity in BTUs/hr X # hours operated
SEER #
X cost per kWh = savings per year
1000 Watts per kilowatt
Whatever type of air conditioner you buy, remember the EER rating! You might save more money by paying a little more up front.
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- What else should I know about air conditioners before I buy one?