High-efficiency air conditioners cost more initially, but result in the
lowest energy bills and often have additional energy-saving features.
High-efficiency air conditioners make sense for those who want to make a
long-term investment in a central air conditioner, live in
an area with high electricity rates or long air conditioning seasons, or
are willing to pay more at the time of purchase to reduce use of
electricity for social/environmental reasons. Most models are two-stage
units, which cool efficiently with less on/off cycling. All use the more
environmentally friendly coolant R-410A instead of R-22 (Freon).
Adco will determine the correct size by estimating your cooling and
heating loads, which are specified in either British Thermal Units
(BTUs) per hour or tons. (12,000 BTU/hr is equivalent to one ton.) Load
is computed based on the size of your house, the climate in your area,
and other factors such as shade, glass area and ventilation. If your air
conditioner is undersized, it won't cool effectively. But if it's
oversized, it will cool in short blasts and then turn off. This
increases temperature variability and doesn't reduce humidity as
effectively. Make sure your contractor does a Manual J cooling-load
calculation, however, and not just a rule-of-thumb estimate based on
house size.
Units with high SEER specifications often cost more to buy and but less
to operate. Be sure to find out about local utility and government
rebates. They may offset all or most of the cost difference between a 13
SEER air conditioner and a high-efficiency model.
Scroll compressors have fewer moving parts than the older, reciprocating
compressors, and are more reliable. Scroll compressors are also quieter
and more efficient. However, because of their smaller volume, they are
less forgiving if liquid refrigerant flooding should occur due to
overcharging of the system. Compressors are the most expensive
components in air conditioners, but most air conditioners have ten-year
limited warranties. Reciprocating compressors are still used in some
budget models, but are no longer common.
Some cheaper models still use R-22 refrigerant (often called Freon).
Freon damages the atmosphere's ozone layer and is being phased out. R-22
units will not be manufactured after 2009 and the refrigerant will
eventually no longer be available. Most air conditioners now use R-410A,
which in the short run is more expensive.
Look for sound-dampening features such as vibration isolation for the
compressor and insulation. Also, louvers or heavy-duty wire grids and
caps protect the unit from weather and impacts from sports or lawn
equipment. If noise concerns you, ask prospective contractors for the
decibel ratings of the units they are proposing.
Costs can vary significantly depending on what systems, if any, already
exist in your home. If you have no ductwork, or your ductwork is old and
leaky and needs replacement, the project cost will be more than what
you'll pay if a new air conditioner can be connected to the existing
ductwork.
Consider a two-stage air conditioner for maximum comfort and efficiency.
These high-end units use two compressors and fans. They cost about 30
percent more than a single-stage air conditioner.
