Deciding on what size air conditioner you
need is not as simple as it looks, but here are some of the
factors that we suggest our customers consider. Take for instance
an air conditioning unit rated by the manufacturer at 9000
BTUs, which based on normal conditions will cool an area up
to 300 square feet with an average ceiling height of 8 feet.
However, there are additional factors that can affect how
much cooling is necessary to reduce the air temperature in
the room to a satisfactory level and maintain it there.
For instance, you would need to add approximately
600 to 800 BTUs for each person in the room. Also, if you
have computers running, motors, or lights on, it will add
to the heat given off in a room and thus increase your cooling
demands. In addition, if the room allows a great deal of sunlight
to come in, this will add to the amount of cooling you will
need. We recommend turning off unnecessary lights and leaving
the shades down on windows on hot days. Ceiling fans can also
make for your feeling cooler, although the temperature may
remain the same.
Another important thing to consider when cooling
an area is the humidity. For example, running your air conditioner
on 65 degrees may be necessary for you to feel cool if the
humidity is high in the room. However, if the humidity is
controlled, let's say between 40 and 50 percent, most people
will find it too cold if the air conditioner cools the room
down to 72 degrees. Many people now supplement their central
air conditioning with dehumidifiers because the air conditioning
units are either oversized for their area or they are the
newer models that are designed to dehumidify less so as to
attain a better EER energy rating. When an air conditioner
dehumidifies the air, heat is given off by the condensation
process and more BTUs are required to cool the air, therefore
reducing the product's energy rating. Without having separate
dehumidification, it is necessary to set the thermostat way
down to 65 degrees so it runs longer and dehumidifies the
air. The problem is it ends up being too cold not to mention
the energy used. Many people find they can set the thermostat
on their central air conditioning on 75 to 80 degrees and
be comfortable as long as the humidity is at a comfortable
level.
See
our comparison chart on our complete selection of portable
air conditioners
First Published: mid July 2003
Updated: April 2007
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