It is the capacity to cool the air in the room and is generally measured in Tonnes (or Tons). The tonnage of an airconditioner depends on its BTU/hr (British Thermal Units per hour) value.

As a thumb rule, divide the square feet area of your room by 600 to arrive at the basic tonnage capacity required. Add 0.5 tonnes for every 10 people occupying the room at the same time. Similarly add 0.5 tonnes for every 1500 watts of appliances or lighting present in the room (A computer would consume about 300 watts and a regular bulb, 40 to 60 watts). Always round off on the higher side. However, this calculation is very subjective and each manufacturer has his own calculations for measuring required tonnage. Very often manufacturers calculations suggest a number that is very high and your own discretion is required when you actually decide to buy.

Choosing the correct cooling capacity helps reduce your electricity bills. A larger air conditioner than what is required not only costs more but cools too quickly, switching on and off at very short intervals. This leaves the room unpleasantly cold and humid. On the other hand an air conditioner that is small for the room will take a longer period to cool the room and will not give very good results.

Energy Efficiency Ratio measures the cooling efficiency of the air conditioner compared to the power it consumes.

It is the ratio of the cooling capacity in BTU/hr to its electricity consumption in watts.

It is in your best interest to buy machines with higher EERs as they are more energy efficient and can save on electricity consumption.

Compressor Type states the type of compressor that your air conditioner has. They are of two types: reciprocating or rotary.

The compressor in the AC circulates the refrigerant through all the refrigeration system parts to provide uninterrupted cooling in the room. Compressor is the most important part and is often called The Heart of the refrigeration system. There are of two types: reciprocating or rotary.

Rotary compressors are silent and generate less vibrations as compared to reciprocating compressors. Reciprocating compressors are generally less expensive and not as power efficient and silent as the ones fitted with a rotary compressor. Rotary compressors are not repairable, when the failure occurs out of warranty period. Reciprocating compressors are repairable – mostly by respective compressor manufacturers in India.

The refrigerant gas is the substance that flows through the various components and coils of the air conditioner such as the evaporator, compressor and condenser to remove heat and cool the environment. The weight of the refrigerant (measured in grams). R-22 is a long-time standard refrigerant used in cooling products.

The number of settings at which the fan of the air conditioner can operate (just like the regulator of a ceiling fan).

More fan settings are preferred as it gives the user a wider choice of speeds at which the air conditioner blows the air.

It is the maximum speed at which the fan can possibly rotate.

The speed of the fan is measured in RPM (rotations per minute). A higher maximum speed indicates that the air conditioner is able to blow a stronger stream of air into the room.

Air flow is the circulation of cold air from the machine. It is measured as M3 per hour. Higher the air flow or circulation better is the cooling.

It is the ability of the air conditioner to remove moisture from the air as it cools.

This makes the room more comfortable and decreases humidity. This is one of the reasons why air conditioners are so effective in humid areas and preferred over air-coolers which are used in the dryer regions of interior and western India.

A filter purifies the air that goes through the air conditioner. Slide in/ Slide out filters and Pop-up filters allow easy maintenance as they can be removed for cleaning without opening or dismantling the entire machine.

There are different types of filters, which remove dust, germs, bacteria, odour, etc. Deodourising filters remove dust particles, dirt, and tobacco smoke and absorb odour-generating particles. Anti bacterial and anti fungal filters clean the air and remove germs and bacteria thus reducing respiratory problems. The Electrostatic filter removes dust particles as small as 0.01 microns cleaning the air of dirt, dust and tobacco smoke etc. The Ionisation filter restores the balance between postitive and negative ions, thus reducing domestic pollution.

Filters help to improve air freshness. It is very necessary that the air conditioner you choose not just cools the air, but also cleans the air. Go in for air conditioners that have built-in deodorizer and special filters that remove bacteria and dust.

It is a type of filter. It absorbs smoke and odour-generating particles like tobacco smoke, etc. Leaves the room smelling fresh.

It is a type of filter. Filters clean the air as it flows through the airconditioner. The anti-fungal filter removes bacteria and fungus present in the air.

This is a boon for people with respiratory problems and those who live in humid areas.

It is a type of filter which gives particles of dust electric charge. This causes particles to be attracted to a plate so they can be removed from air stream or atmosphere.

It is a type of filter which cleans the air from smoke, dust and germs. Filters clean the air as it flows through the airconditioner. Ionising Filters generate negative ions which combine with positive ions in the air to give clean air, free of smoke, dust and germs.

Helps to keep the room smoke-free thus keeping the air in it smelling fresh.

The body and chassis of air conditioners is prone to corrosion. However, if the body is made of galvanized steel or is powder coated it helps in protecting the unit from corrosion and extends the life of the body.

Noise level is measured in decibels and is the level of sound generated by the appliance during operation.

Air conditioners with rotary compressors generally make less noise than a reciprocating compressor. A normal human ear is capable of hearing 15 decibels of noise and above. Just to give you an idea, 40 decibels of noise is what you hear at night in a residential area, and 50 decibels is what you can hear in a quiet restaurant. 60 decibels is the sound created by two persons in conversation. Make sure that your air conditioner does not make a droning sound during operation.

The running current is the current consumed during operation of the window air conditioner.

Higher the cooling capacity, greater will be the current used during operation, and higher will be the electricity bill. Hence, it is very important to opt for the lowest current from amongst air conditioners of the same tonnage.