Stages usually mean an Air Conditioner can run at different cooling capacities by varying the speed of the compressor and fans, or in the case of a Heat Pump cooling and heating capacities.
Please note an important fact. It usually takes about 5 minutes or more for an air conditioning system to get up to full or selected capacity. It is like driving a car, stop and go driving uses a lot more energy than highway driving.
Make Sure Your Air Conditioner is the Correct Size
Here is another important fact. Americans a lot of the time think bigger is better. This is not so with air conditioning. If it’s too big it will start and stop too often leading to energy waste and poor humidity control. It can not remove humidity if it is not running. A system that is the correct size will cool most of the time on the very hot summer days and cycle more on cooler days.
Single Stage Air Conditioners
Single Stage runs at 100% capacities any time it is on. Once it reaches temperature set point it shuts off. When the thermostat calls for cooling again it starts again. This system will cool your house and the ones being sold today will most likely save you money if you are replacing a single stage unit. This is a good choice if you need a good, but lower priced system. This would be good if you know you are going to be moving within the next few years. You would probably not get a payback from going with higher priced unit. It would be a particularly good choice for rental properties.
Two Stage Air Conditioners
Two Stage air conditioning systems have on stage that operates at about 70% capacity and one stage the operates at 100% capacity. It will use the lower capacity first and if it can not cool enough will switch to the higher capacity. It will shift back down the lower capacity when it can. The idea is not to have too many starts and stops thus saving energy and better humidity control. As we know living in the Bryan/College Station area humidity can be brutal. If we can lower the humidity, we can set the temperature a degree or two higher and still be very comfortable.
Multiple Stage Systems…A Personal Favorite
Multiple Stage Systems are my favorite. Heil makes a 5 stage system that runs most of the time, thus less on and off. It tries to match the capacity to the head coming in. This is the most efficient way to cool and dehumidify. The homeowner can set the humidity he wants in the house on the thermostat.