Question

What to look for when buying an air conditioner?

Answer 1

Air Conditioner is an appliance that can significantly blow up your electricity bills and utmost care should be taken while buying one. Please note an air conditioner bought once will go on for next 10 years at least and thus it is important to make a right decision.

Right sizing an air conditioner is very important.This can significantly impact your electricity bills and size here means tonnage of air conditioner

Sizing of an air conditioner:Size of the room - This determines the amount of air in the room that needs to be cooled.
Number of people in the room - Every human being emits heat and air conditioner needs to cool it.
Amount of stuff kept in the room - Please note every item kept in the room will get cooled from the air conditioner, so lesser the stuff, lesser the electricity air conditioner will consume.
Number of electrical appliances in the room - Most electrical appliances emit heat, especially lights (Incandescent light bulbs can increase cooling load).
Windows in the room - More the windows, more is the heat coming from outside. Well-insulated windows reduce cooling load.
Walls facing the sun - It can increase the cooling load.
Efficiency:
After sizing comes the efficiency, the efficiency of an air conditioner is usually termed as EER (Energy Efficiency Ratio) 

EER = Amount of energy removed (Btu/hr) / Power Consumed (W)

Every air conditioner has a cooling capacity, which is represented in BTU/hr. It is the BTUs of heat that it can remove in an hour.

If the heat coming in the room (in BTUs) is more than the heat that air conditioner can remove, then the air conditioner will not be as effective. Thus an undersized air conditioner cannot remove heat effectively and the compressor of the air conditioner will continue running all the time thereby consuming more electricity.

Thus, higher the amount of heat removed per hour per unit of power consumed, higher is the efficiency of air conditioner. Also, higher the EER, better is the air conditioner.

Whenever we go to buy a new air conditioner, we find a label on the same. This is probably. the most important factor apart from the cost, which determines the selection of an air conditioner. Bureau of Energy Efficiency (BEE) mandates every air conditioner to have this label.