How to calculate the right size central air conditioner for your house
To get a ballpark size estimate for your house. First, the old-school equation: ((House square footage times 25, divided by 12,000) – 0.5) = required tons. So for instance, a 1,500 square foot home would look something like this
1) 1,500 X 25 = 37,500
2) 37,500 / 12,000 = 3.1
3) 3.1 – 0.5 = 2.6 So you’d need a 2.5 or a 3-ton sized central air conditioning unit.
Energy Efficiency Considerations
Select a central air conditioner with as high a SEER2 as is practical within your budget. The annual cooling efficiency of a central air conditioner is affected by the manufacturer's choice of features and components. The SEER2 of central air conditioners ranges from a minimum of 10.0 to a maximum of about 23.0.
An ENERGY STAR® qualified central air conditioner must have a SEER2 (Seasonal Energy Efficiency Ratio) rating of at least 14 or greater. More efficient compressors, larger and more effective heat exchanger surfaces, improved refrigerant flow and other features are largely responsible for recent improvements in the efficiency of central air conditioners.
Advanced reciprocating, scroll and variable-speed or two-speed compressors, when combined with the current best heat exchangers and controls, permit SEER2s as high as 23.0. Central air conditioners with the highest SEER2s always use variable-speed or two-speed high-efficiency compressors.
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