Installing or replacing a central air conditioner is one of the most significant home improvements you can make in terms of comfort. It’s worth doing homework. We only need to consider the following 7 points.
1. Select Staging or Variable Speed Compressors
First, we need to select the type of air conditioner. According to efficiency, air conditioners are divided into single-stage, two-stage, and variable-speed compressors. What you choose will determine your level of A/C efficiency and comfort.
Single-Stage: A single-stage unit can either be off or on at full capacity. It will operate at full capacity regardless of how much cooling is required. Because air conditioning systems are sized to provide adequate cooling on the hottest day of the year, this means single-stage systems often provide more cooling than is required. This reduces the efficiency of the system and can lead to uncomfortable conditions.
Two-stage: Two-stage compressors help address this mismatch of cooling needs and system output. A unit equipped with a two-stage compressor will have two distinct levels of cooling output, typically called the low and high stages. The high stage will have sufficient capacity to maintain comfortable temperatures in extreme weather, while the low stage will allow for efficient operation during mild conditions.
Variable Speed: Variable-speed compressors are the full-out extension of two-stage compressors. Rather than having specific output levels at which to operate, a variable speed unit can produce any output within a range. This range will vary from model to model and will enable the unit to match the required cooling or heating load in real time and maximize comfort and efficiency.
Two-stage and variable-speed units often have a higher rated efficiency than single-stage models, but even if all three of these units had the same rated efficiency, the longer cycles of a two-stage unit would save approximately 3 percent over a single-stage model, and a variable-speed model would offer savings of roughly 7 percent.
2. Select Air Conditioner Efficiency Ratings
Air conditioner efficiency is rated in SEER2 (Seasonal Energy Efficiency Ratio). An air conditioner’s SEER2 rating is arrived at by dividing the total cooling output from a piece of equipment in BTUs by the energy it consumes in watt-hours. Most central air conditioners today have a SEER rating between 13 and 20, with those at the higher end of this range considered very energy efficient.
It’s important to note, however, that the efficiency of a system and its SEER2 rating depend on all the components in the system and not just the condenser. The SEER2 rating for a condenser is primarily used for marketing and product differentiation, and you should always use the rating for a complete matched system when comparing options.
Consider the Local Climate
In climates that are both hot and humid, the SEER will need to be higher since the air conditioner will be running more often to cool and dehumidify the air.
3. Select the Size of the Air Conditioning Unit in BTU
One thing that may be confusing when you are shopping for a new central air conditioner is how the size is referenced. An air conditioner’s cooling capacity is measured in a size known as British thermal units per hour (BTU). This is sometimes referred to as “tons,” which doesn’t refer to the weight of the unit, but the BTU/hour, or cooling power. One ton of cooling power equals 12,000 BTU/hr.
Your HVAC contractor should inspect the interior and layout of your home, as well as the raw square footage. They will use this information to make a recommendation for the proper-sized AC system.
If your central air conditioning system is too large, it will cycle on and off throughout the day, which can waste electricity. When the central air conditioner is too small, it will not be able to cool your home sufficiently.
Make sure your central air conditioner system is sized correctly. There is more to consider than just the square footage of your home! Be sure to choose a contractor who will size your central AC system according to Manual J, a standard developed by the Air Conditioning Contractors of America (ACCA).