There are many types of ac systems, but generally the efficiency of your hvac system will come down to staging and proper air conditioning installation. Equipment staging or speed simply refers to the speed of your compressor in your outdoor unit, not to be confused with the speed of the indoor unit. Generally speaking there are 3 types of staging in modern equipment; single, dual, and variable. Single stage equipment is in the lower efficiency units, dual is slightly more efficient, and variable is the most efficient of the 3.
Single stage hvac systems are the most common of the three types of ac systems. They are simple enough to understand, they are either at 100% or 0. It is a simple on or off. Single stage units are the most affordable and most common unit on the market, but provide little in the way of efficiency. The upside of single stage air conditioning installation is mainly price related. Not only are they more affordable to put in, but the parts for these units tend to be simpler and less. expensive to replace. On the downside they do little to reduce the cost of operation. Due to the lack of being able to adjust for different heat loads on the house throughout the day and different seasons they are not well suited for tightly built, well insulated homes. For more info on this please see our insulation section and spray foam considerations.
Their operation from the thermostat is generally controlled by room condition only.
Dual stage hvac systems are a step up in a lot of ways from single stage units. They give you some variance in system size by having a low and high stage. These types of ac systems allow them to adjust to the conditions in the home and control the run time to more efficiently cool. Generally the majority of your runtime is done well below the peak load so the dual stage allows for essentially a smaller system to run when necessary. With proper air conditioning installation they will run longer than single stage systems in an effort to provide a more comfortable home while saving electricity by eliminating the constant on and off of a short cycle.
Variable Speed Systems are often confused with variable speed indoor units. A variable speed hvac system not only has a variable speed indoor fan but a variable speed outdoor unit. These types of ac systems often do have variable speed indoor units but not all variable speed indoor units have variable speed systems. When considering air conditioning installation make sure to clarify with your contractor if the fan or the system is variable speed. The compressor on the outside of a variable speed system will vary with any changing condition often being capable of going from .01 tons to 5 tons. Obviously this is a huge step up in efficiency and comfort from even the dual stage system. They run longer than a single or dual stage system; however, it is not a bad thing as they will still use less power while controlling humidity and temperature to more precise levels. I have many customers in Granbury and Glen Rose who love not only the savings they get from the unit but the quiet operation of these types of systems.