Air conditioner size calculator
Cooling load is the heat you have to remove: through the fabric, through the glass, from people and from everything plugged in.
W/m2
About 100 to 130 W/m2 for a typical office or living room.
W
W/m2
Cooling capacity needed
15 048BTU/h
- In kilowatts
- 4.410
- In tons of refrigeration
- 1.254
- With a 10% margin
- 4851
- Solar gain through glass
- 1000
- Heat from occupants
- 360
- Load per square metre
- 176.4 W/m2
Show the working
- Floor area = 25
- Base load = 110
- People = 3
- Heat per person = 120
- Equipment load = 300
- Sunlit glazing = 4
- Solar gain = 250
- fabric = 25 * 110 = 2750
- Heat from occupants = 3 * 120 = 360
- Solar gain through glass = 4 * 250 = 1000
- total = 2750 + 360 + 300 + 1000 = 4410
- Cooling capacity needed = 4410 * 3.412141633 = 15 047.5
- In kilowatts = 4410 / 1000 = 4.41
- In tons of refrigeration = 4410 / 3516.8528420667 = 1.253 96
- With a 10% margin = 4410 * 1.1 = 4851
- Load per square metre = 25 > 0 ? 4410/25 : 0 = 176.4
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- total = fabric + occupants + equipment + solar gain
- 1 ton of refrigeration = 3516.85 W
Oversizing an air conditioner is worse than undersizing: it short-cycles, never runs long enough to dehumidify, and leaves the room clammy.
Solar gain through unshaded south-facing glass can exceed the entire fabric load.