You may have reached this by looking for what the difference is in cost and what someone means when they say staged or variable speed in relation to A\C. Before replacing your unit, let’s discuss what these terms mean in hopes of making a better choice.
Staged – particularly single staged – means that an air conditioning or furnace unit has one speed. All the way ON or all the way OFF. When the temperature sensor trips to meet the programmed number, the unit turns all the way on until it is reached and then turns itself off. A Two-Stage system would be more like a High and Low gear in a car. If your home’s air conditioning unit is 10 or more years old, chances are it is a Single Staged system. They are the least energy efficient because naturally, they can only draw power at one rate- all ON or all OFF.
Multiple Stage equipment is more like changing gears on a bike. They are not as able to incrementally change as a variable speed compressor, but they will have two “stages” – think around 10 “stages” that have different power outputs. Multi-speed, or variable speed, air conditioners ramp up or down in tiny increments depending on the “load” or how much cooling is needed to get the job done. These refer to the compressor or blower and its ability to match the needs of the environment as opposed to just turning full on or being off. You only have one system year round, so having a variable speed compressor lets your system appropriately adjust. If the temperature is milder, it may not take as much cooling to get to your set temp, and this translates to savings in energy usage as the machine doesn’t need to run at full blast only.
You should notice a difference in energy usage and sound. When a variable speed unit starts blowing at a slow speed and increases as the heating or cooling needs to increase, it is quieter than what you are probably used to. Also, air is continually being cleaned with a variable speed blower. Single-stage systems will come on more frequently, for less time but with a large power pull when it starts up and runs. It tends to wear out the system earlier due to being hard on working parts to go from 0 to Full Blast and also uses more energy to cycle more often.
Variable speed systems run for a longer period, using less energy and more evenly heating or cooling your home.