Window AC Units – What Size Do You Really Need?

If you want to cool a small room this summer, buying a window air conditioner unit is cheaper than buying an air conditioning system for the whole house. The cost will be cheaper and so will your energy bills.

The size of the unit is important when selecting window AC units.  An air conditioner that is not powerful enough for the room may run all the time and not cool off the room efficiently.

If you purchase a window air conditioning unit that’s too powerful for the room it could end up using more electricity to run. Actually, running a unit that is the correct size for the room could use less energy to cool a room than running a bigger air conditioner for a short time period.  Just remember bigger window AC units are not necessarily better or cost efficient.  Also, a unit that is too large for the room may not run long enough to remove the humidity from the the air.  Just remember that window AC units need to be the correct size for the room, in order to cool and remove humidity properly.

How to measure your room correctly in order to select the correct window air conditioner size:

First you need to know the square feet.  Just multiply the width of the room by the length of the room in order to know the size of the room you are trying to cool.  For example, a room that is 15 feet by 25 feet has 375 square feet.

The cooling capacity of  Window AC Units are measured in British Thermal Units (BTUs) per hour.

Window AC Units for the Room Size:

5,000 BTUs for 100 – 150 square feet
6,000 BTUs for 150  – 250 square feet
7,000 BTUs for 250 – 300 square feet
8,000 BTUs for 300 – 350 square feet
9,000 BTUs for 350 – 400 square feet
10,000 BTUs for 400 – 450 square feet
12,000 BTUs for 450 – 550 square feet
14,000 BTUs for 550 – 700 square feet
18,000 BTUs for 700 – 1000 square feet
24,000 BTUs for 1,000 – 1400 square feet

Other factors to consider when buying Window AC Units:

  • Heavily shaded rooms need less BTUs, approximately 10%
  • Sunny rooms will need more BTUs, approximately 10%
  • Kitchens require more capacity, approximately 4,000 BTUs
  • Energy Efficiency Ratio (EER), the higher the rating the better, cost less to operate

ENERGY STAR® ratings are another factor to consider when purchasing window AC units.  Window Air Conditioners that have this rating have high-efficiency components.  The compressor doesn’t run continuously thus reducing energy costs.  Another feature to look for in a window air conditioner is a unit that has a 3 speed fan controls.  Digital thermostats are beneficial because you can set an exact room temperature.  Timers are also useful because you can have the air conditioner turned off while you are at work and then set it to come on an hour or so before you get home from work.  One last thing to remember, always clean the unit’s air filter.  When you keep the air conditioner’s filter clean, it not only reduces energy costs, but also is healthier for you. Now you know what to look for when buying window AC units.