Steps 

1.Shop for an air conditioner in the cooler months. Many brands are more likely to be on sale and in stock. 

2.Decide between a window, portable or wall air conditioning unit. Unlike window units, portable units do not need to be mounted in a window. They are usually on wheels and are vented through a hose placed in a window. Wall units are placed in holes cut into exterior walls. 

4.Check the cooling capacity. This is measured in BTUs per hour; higher BTUs mean more cooling capacity. 

 5.Compare the Energy Efficiency Rating (EER) of air conditioners. The EER is required to be displayed on modern air conditioners. Units with higher EER ratings use less energy. 

6.Make sure the louvers of the air conditioner are motorized or adjustable. Air needs to be aimed at the center of a room to provide adequate cooling. If the window is off-center, the vent will need to be adjusted to the correct position. Some models have rotating louvers to circulate air. 

7.Consider special features. Some air conditioners have remote controls, making it easier to adjust the settings from across the room. Timers are another beneficial feature; they allow you to program different power levels for different times of the day or turn on the air conditioner before you get home from work. Look for filters to remove dust, odors and allergens. 

8.Get advice and feedback. Read reviews and model comparisons from reliable sources and consumer sites. Be on the lookout for complaints about specific models or companies. Ask for advice about how to buy an air conditioner from family and friends who have recently purchased one. 

 9.Try out the air conditioning unit in the store. Use it in the store to check on the noise level and ease in operating. 

 10.Find out how to install the unit. Some air conditioners require additional hardware or 220 volt electrical wiring. Make sure the unit is the right size for your window or opening. If necessary, choose a retailer that offers installation service. While this may cost more, it could save time, frustration and injury. Many units are awkward and cannot be installed by just 1 person.