There are a number of factors to consider when shopping for a window air conditioner unit. These factors will have a lot to do with the functionality and efficiency of the unit, and have a significant effect on operating cost as well.
Cooling power. Cooling power is typically measured in British Thermal Units (BTU). Most units designed for home use provide about 5,000 BTUs. This is sufficient to cool most average-sized rooms regardless of environmental conditions. For much larger rooms, you will probably have to go with a much higher rated air conditioner. Keep in mind, however, that higher BTUs will also equate to increased electrical consumption, which means your electric bill will go up as well.
Automatic controls. Being able to adjust the controls manually is essential for optimum operation of the air conditioner unit. But you should also look into units that offer a good degree of automatic control. These could be used to turn the AC on and off at specific times, or when the temperature and humidity in the room reach a certain range. Some AC units will even give you the option to shut them off automatically when a user-defined temperature is reached. This feature not only results in more convenient operation. It also reduces electrical costs by turning off the AC when the room is cool enough.
Power consumption. The amount of power consumed is an equally important consideration. During the hot summer months, you will want a unit that performs as efficiently as possible. This could mean a unit that cools a room quickly and shuts off–thereby saving power–or one that detects temperature and humidity conditions and turns on and off accordingly. As mentioned previously, air conditioners that provide more cooling power will use up more electricity. When choosing an air conditioner, you should therefore go with a model that can cool your space effectively without using up too much power.
Noise. You will probably use your AC mostly at night when you are asleep. You should therefore ensure that the unit you purchase doesn’t produce excessive noise. This can be a lot more challenging than you think, especially with powerful ACs. Oftentimes, some degree of noise is pretty much unavoidable with powerful units. That being said, modern air conditioner designs tend to be a lot more efficient, and they could effectively cool your space without producing too much noise. Careful comparison shopping will enable you to find a unit that provides a good balance between cooling power and low-noise operation.