Window-mounted and wall-mounted air conditioners are often used in apartments, condos and in older homes. (They are also known as room air conditioners, which is how I will refer to them for the remainder of this blog, for practical purposes.) Room air conditioners are not particularly efficient when you compare their ratings to the energy efficiency ratings of central air conditioners. However, room AC might be the better option in some cases.
• Homes with central AC usually maintain a lower temperature in more rooms than those with room air conditioners. Central AC cools even unoccupied rooms whereas room units cool only the one or two rooms in the house that actually require cooling.
• Central air conditioners often have ducts in attics that are unconditioned meaning that up to 20% of the air conditioner’s output is being wasted through the unfinished attic. If you are building a new home and installing central AC, make sure that your HVAC contractor locates all duct work inside the home with none in the unconditioned attic.
• Room air conditioners are often noisy, so homeowners remember to turn them off when they leave the room and turn them down at night. Generally speaking, homeowners with central AC leave the air conditioning on all day and night, even when there is no one home, thus, wasting unnecessary energy. The solution here is quite simple, no matter what type of unit you have: turn off your air conditioning when you aren’t going to be home.
• Installing two or three Energy Star rated room air conditioners can cost less than installing central AC.
• If you live in a northern climate where you only need to air condition your home for 10-20 days per year, installing room air conditioners should suffice.
The proper installation and maintenance of a room air conditioner will determine its real efficiency. In many cases, units are stuck into windows with thin corrugated panels on either side to cover the window gap, meaning that the air you’re cooling in the house simply leaks out along the edges. The best way to mount a room AC is by having an air conditioning expert install a custom through-the-wall box that is carefully gasketed to prevent air leaks.
If you found this blog post interesting, you may also want to read Improving the Efficiency of Your Heating and Cooling System and Water ConservationTips – Savings Around the House.