conditioners have come a long way from the days of fans and
window units. Early air conditioners were noisy, inefficient
and costly to operate. Today's central air units have made great
strides in all three areas.
The cost to install a central air conditioner will vary greatly
depending on the size of your home and the amount of work
that needs to be done. If the air conditioner can be attached
to duct work, the cost will be much less than if new duct
work has to be added, particularly if the ducts have to be
run through walls (thus requiring drywall repair and replacement).
There are ductless systems available, but they're not widely
used in the United States, where most homes have duct work,
or at least the space for it. The duct-free systems tend to
be more expensive, but it may be worth comparing price if
you have to have ducts added anyway.
When considering a new air conditioning system, there are
two factors, or gauges of measurement, to consider:
Energy efficiency. The U.S. government has created a set
of standards, known as the Seasonal Energy Efficiency Rating
(SEER), which manufacturers use to test their central air
conditioning systems. The systems are then assigned a SEER
rating. The higher the rating, the lower the operating cost,
because the higher rating indicates a system which uses less
electricity. Government standards require new systems to have
a SEER rating of at least 10, but many newer models boast
a rating of 18 or more. Be aware that the higher the SEER
rating, the higher the price. However, many HVAC experts and
homeowners feel that the additional cost will be paid back
in long-term energy savings, particularly in climates where
an air conditioner is used year-round.
Cooling capacity. This is not as easy to define as the SEER
rating. Cooling capacity refers to the number of "tons"
of cooling, with one ton equal to 12,000 Btu per hour. This
is harder to gauge, because the "tons" will vary
hour to hour, morning to night, depending on the weather and
the home's cooling needs. A general rule of thumb is that
the larger the capacity, the higher the cost to pay for the
equipment, and the more electricity needed to run it.
Determining what cooling capacity your home requires is tricky,
and it's wise to go over your home's environment with your
contractor so they can help you make an informed choice. Factors
involved include the size of the home, level of insulation,
amount of direct sunlight (particularly from windows which
face east or west, which let in the most light and heat),
and whether the house is in the open or shaded by trees. If
anything, an undersized air conditioning system is better
than one that's too big. An overly large system will run more
often but won't dehumidify the home as efficiently as a smaller
Note: many power companies can put a device (often called
a "saver switch") on your central air conditioner
at no charge. This switch operates during peak energy consumption
hours (usually during the work week), and it turns the air
conditioner off for a few minutes every hour. This may raise
the overall temperature in the home by a degree or two, but
it provides considerable cost and energy savings. It's well
worth the slightly warmer temperature.