2-stage cooling is a method of cooling that can better manage the cooling of your home while outdoor temperatures are changing. It can also better maximize indoor comfort and energy efficiency. 2-stage cooling systems are typically the most energy efficient systems out there.
 
2-stage cooling can be done by having one unit with two compressors, one small and one large. The small one is typically capable of putting out about 50% the capacity of the larger one. The second way to have 2-stage cooling is to have a single scroll unloading compressor. This compressor can unload its capacity down to about 66% of maximum capacity. Both these methods of getting 2-stage cooling allow the unit to run at a lower stage when the high stage is not needed. By doing this, energy is saved. It is the same principle that is used in car engines that have the ability to drop out cylinders when they are not needed.
What is 2-stage heating?
2-stage heating has the same principle as 2-stage cooling. It allows the unit to adjust itself based on the amount of heating that is necessary. 2-stage heating is a good way to save on heating costs.
 
A heat pump system would have two different sized compressors, a small and a large one. The compressor that is used at a given time would depend upon the need. If only a small amount of heating is necessary, the smaller compressor would be used to save energy. The large compressor would only be used when a large amount of heating was needed.
 
A gas furnace that is 2-stage has a modulating gas valve that regulates gas flow depending upon the need.
What is “variable speed”?
Variable speed refers to an indoor motor that changes speed. This type of motor increases speed and airflow from start up to full capacity over a span of 8 minutes. This results in quieter start-up and shut down of the system. This motor is also about 5 times more efficient than a conventional indoor fan motor.
What does “ton” mean when referring to air conditioning? Example: I have a 4-ton air conditioning unit on my home.
Air conditioning units are sized in tons. One ton is equal to 12,000 BTU’s of total capacity. So, for example, a 4-ton air conditioning unit has a total capacity of 48,000 BTU’s while a 2-ton machine only has a total capacity of 24,000 BTU’s.