What is a Split Duct Unit? They are units that can act as both Air Source Heat Pump and Central Air Conditioner Equipment These units are rated in British Thermal Units (BTU). BTU is the amount of heat required to raise the temperature of 1 pound of liquid water by 1 degree F at a constant pressure of one atmosphere. As with calorie, several BTU definitions exist, which are based on different water temperatures and therefore vary by up to 0.5%. A BTU can be approximated as the heat produced by burning a single wooden match or as the amount of energy it takes to lift a one-pound weight 778 feet.
So now you have figured out what size you need, what next. You should look at efficiency. Efficiency can be measured by Seasonal Energy Efficiency Ratio (SEER). The higher the SEER, the less energy it uses. Divide the BTU's by the SEER to determione how much power the unit will draw. A 9,000 BTU unit with a SEER rating of 30, will draw 300 watts of electricity. Compare that to a unit with a SEER rating of 20, that unit will draw much more electricity - 450 watts.
The Energy Efficiency Ratio (EER) is a better way to measure efficiency for a cooling device. It is the ratio of output cooling (in BTU) to input electrical power (in Wh) at a given operating point. EER is generally calculated using a 95 degrees F outside temp and an inside (actually return air) temp of 80 degrees F and 50% relative humidity. The EER is a more realistic measurement of energy efficiency in warmer climates due to the high demand and higher cost of peak hour electricity. Again, the higher the number, the more efficient the unit.
People often think of Mitsubishi as being the industry leader. But a check of the ENERGY STAR website does not have one unit listed. The units that consistantly have the highest ratings are Fuijitsu. But don't take our word for it, check the site yourself.