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Before you buy an AC

Buying an AC that suits both your room and your pocket need not be a difficult task. We show you how

Cut back on power

Use your AC correctly to ensure that your electricity bill doesn’t skyrocket

Check the EER

The Bureau of Energy Efficiency has rated most ACs.A unit with a higher star rating will consume less electricity than a lower star rated one

Use fans
Set AC at a higher temperature and use a ceiling fan. Ceiling fans cost about 30 paise an hour to use while ACs cost about Rs 10 an hour

Clean the filter
Keeping the filter clean can lower energy consumption by 5-15%

Shade AC
Shading your AC from direct sunlight boosts efficiency by 5%

Get rid of old repairprone AC.New one will work out cheaper on life cycle costing

Winter’s just a dream and a nightmare summer is upon us. There’s hardly a home that doesn’t have at least one air cooler. But coolers, no matter what the ads say, add to the humidity, and what you really, really need at high noon is dry cold. Air-conditioners (AC) are expensive, you say. They need complex installation.

And they consume huge amounts of power. You have a point, but ACs are really not as expensive as you think, if you understand the machine to know what exactly is the capacity and features that you really need. If you really want an AC for the summer but don’t want to pay a packet, you can even think of hiring one. You’ll pay under Rs 5,000 for the use of an AC for four months or so, and installation is free. However, most of these machines are either assembled or souped up antiques, so what you save on buying a new AC, you’ll spend on power. If you have one of those ancient ACs that you plan to recondition, check with an electrician if this is such a good idea. It might cost less to install, but again, your power bills could hit the roof.

A basic decent branded AC costs a little over Rs 10,000 today, and most of them claim to be power efficient. So, you head off to the shops and ask to see the ACs on offer. The first question the dealer will ask is: window or split? The one is not necessarily better than the other. Window ACs are easier to install and cheaper than split ones.

Split ACs come with two separate units—a compressor unit outside the house and one or two units installed inside the house. Hence, installation charges are higher. But split ACs score over their window versions in terms of being quieter, more aesthetically pleasing and having better air distribution. That’s why a 1-ton split AC, for instance, will cost approximately Rs 5,000 more than its window counterpart, but it will also be about 15 decibels quieter.

The most important feature to consider before buying an AC is its cooling capacity. This is measured in British Thermal Units per hour (Btu/hr) and indicates the quantity of heat a room AC can remove in an hour. It ranges between 5,000 and 24,000. In layman’s term, where we are more used to referring to an AC in tonnage, one “ton” equals 12,000 Btu. The higher the Btu, the more cooling power the unit has. But this does not mean you should buy the highest Btu that your budget allows. Never choose a model with more cooling capacity than required because it will cycle on and off too often, wearing out the machine and not staying on long enough to remove humidity from the air.

Capacity Calculator

• If the room is shaded, reduce Btu by 10%
• If the room receives a lot of sunlight, increase Btu by 10%
• If installing the AC in a kitchen, add 4,000 Btu
• For each person add 600 Btu

Room Size (sq ft)TonnageBTU
Up to 900.89,600
90 - 130
130 - 180
180 - 2302.024,000

How do you know what tonnage to choose? Calculate the size of the room in square feet and multiply that by 35. This will give you a ballpark figure. There are other factors you should consider as well (see table Capacity Calculator), including the ambient temperature, thickness of walls, insulation, size and placement of windows, etc. There are some AC companies that offer online calculators, such as and www.carrierindia. com/onlinesolutions.asp, that take these and other factors into account. Of course, you can take the easy way out by asking an interior designer or electrician for advice.

Some ACs have other features, such as sleep mode which automatically adjusts the temperature during the night, or timers which help you to turn an AC on or off on schedule, or auto restart which restores original settings when power is restored. But extra features also mean you will have to stretch your budget, so check which feature you really need (see box Checklist) and how much you are willing to pay more for it.


Don’t let the dealer smooth-talk you into paying more for fancy features. Here’s what those terms really mean

Rotary compressors are more efficient and quieter than reciprocating ones but are difficult to repair and also cost more

Check if the AC comes with variable fan speeds; you might want to use different speeds for different times of the day

It reduces the amount of humidity in the room. Check for a humidity control button

A deodourising filter removes odour; electrostatic filter clears dust particles; an antifungal one removes bacteria; ionisation filter clears dust and germs

Noise level
On average, this ranges from 30 decibels to 60 decibels. The higher the AC capacity, the more the decibels

Thermostat sensitivity
This determines how closely a unit can maintain a given temperature

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