Choosing your air conditioning system can be an overwhelming task.
Even with the help of a reputable HVAC contractor, there are a wide variety of choices available on the market today. Some research on your own will not only make you more knowledgeable but will also help you ask the right questions so that you can make an educated decision. Selecting the right air conditioning system is crucial to saving you money on energy costs and repairs; to keep your family comfortable, and to meet your needs.
Perhaps one of the most important factors to consider when choosing a new air conditioner is the efficiency rating. Air conditioner efficiency is rated in SEER, short for Seasonal Energy Efficiency Rating. In essence, a SEER rating indicates how much cooling the unit provides for a unit of electricity that is consumed. The higher the number the more efficient the unit and accordingly the less it will cost to provide cooling.Before 1992, most units manufactured had a 6 SEER rating. In order to reduce energy usage, the U.S. Department of Energy established minimum efficiency standards for air conditioners. For our region, current Federal regulation mandates a minimum of 13 SEER. To understand the concept and relative scale of SEER rating, a 12 SEER unit consumes half of the electricity compared to a 6 SEER unit. A 13 SEER unit is 30% more efficient than a 10 SEER unit.
Obviously, the higher the efficiency of the unit (higher SEER), the more the initial cost will be. However, when making a decision, cost savings from the lower use of power consumption should not be ignored as, in the long term, they will outweigh the difference in upfront costs. Although this kind of analysis is specific to each home with many variables to consider including your local utility cost keep in mind that a 16 SEER unit is about 25% more efficient than a 13 SEER unit.
No. of Stages
Most older systems have a single stage of operation, which means they are either on operating at full capacity or they are off. The air conditioner communicates with the thermostat and based on the set temperature, it will run until the set temperature is satisfied. Once the indoor air temperature matches the thermostat temperature, the unit will shut off and the cycle continues.
The two-stage air conditioner can operate at two levels depending on the demand for the equipment. So on very hot days, when demand is maximum, the unit will operate at 100% of its capacity (similar to a single stage system). The second stage of operation kicks in when the demand on the unit is not very high. The capacity at which the second stage operates varies between manufacturers but on average it is about 75% of the total capacity of the system. Although the exact dollar savings are difficult to assess when the unit is operating at 75% of its capacity, it would be consuming 75% of the power it would have consumed if it was a single stage unit. Also, keep in mind the fact that the air conditioner will operate at the reduced capacity for the majority of the time.
Some manufacturers also offer air conditioners with modulating (variable) capacities. A leader in this field is Trane which offers Trane’s TruComfort™ variable speed system, with 700 stages starting at 30% of the system’s capacity. This system offers maximum comfort as having 700stages nearly eliminates temperature fluctuations. The system glides along as if on cruise control, barely sipping electricity for much of the day. It also runs at lower speeds for longer periods of time.
Another important factor to consider when searching for an air conditioner is the noise level it produces. Remember that noise level is measured in decibels (db) and keep in mind that the sound level of whispering in a quiet library is about 30 db’s; sound level of a normal conversation at 3 feet is about 60 db’s, and that of a lawn mower, at 3 feet, is 107 db’s. Multi-stage units offer lower noise levels at lower stages of operation since they would be operating at less than 100% of their capacity. Finally, keep in mind that high noise levels may mean many sleepless nights for you and perhaps your neighbors.
Although this is the single most important thing to consider when buying a new air conditioner, I have listed it last as none of the above factors will matter if the air conditioner is not properly sized. The proper size of the air conditioner depends on many factors including the home area (square footage), orientation with respect to the sun, type and construction material used including insulation, location, windows, and other factors. Prior to final selection, you should insist on load calculations be performed. It is essential that load calculations and equipment sizing be performed by a Professional to ascertain that the designed unit will adequately cool your home without being too large or too small.For more details on AC sizing, refer to How do I determine the size of the air conditioner that I need?