Three types of air conditioners:
The central air conditioner comprises a fan, a compressor and a cooling coil, all of which are housed in a module outside the home. Central air conditioning uses a duct system to distribute cooled air forced from the heating system. It is the most expensive and longest-lasting (more than 15 years) air-conditioning system, providing uniform fresh-air circulation throughout the home. If you don't have forced-air heating, you can turn your attention to a mini- or multi-split air-conditioning system. These systems include a wall-mounted outdoor compressor and a condenser supplying up to three air diffusers. If well maintained, split-system air conditioners can last up to 10 years. If you only have one or two rooms to cool, or if you expect to move any time soon, a room air conditioner – a window unit, a built-in wall unit or a mobile unit you can move from one room to another – may be your best option. A room air conditioner can be expected to keep you cool for at least five years.
Some central air conditioners and mini- or multi-split systems feature a heat pump and are therefore reversible. By drawing heat from outdoors and pumping it into your home, a reversible air conditioner can also serve as a heating system – but only as a backup in the spring and the fall. At temperatures lower than 7oC, it no longer provides the performance you need!
Seasonal energy efficiency ratio (SEER)
To purchase an energy-efficient air conditioner, look for a unit with a minimum SEER ratio of 12. Better yet, opt for an Energy Star model, which consumes at least 20 percent less energy than a conventional unit. And while heat pumps are not eligible for the Energy Star program, Inverter technology – in contrast to conventional reversible air-conditioning systems – gives you the option of varying compressor speeds based on the ambient temperature in your home.
Where a conventional air conditioner stops when the desired temperature is reached, this technology lets the user reduce compressor speed to a minimum. The result? The unit operates on a continuous basis but at a carefully regulated speed – with no costly peak consumption periods.
Some air conditioners are equipped with dual compressors: Approximately 40 percent of the energy is consumed by a smaller compressor, and the primary compressor consumes the remaining 60 percent. When the desired temperature is reached, the primary compressor shuts down and the secondary compressor takes over with its lower consumption ratio. Consumers therefore spend less on energy than they would with a conventional machine, which always operates at 100-percent capacity.