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Ideal Air Conditioner Temperature for Electricity Savings

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Buying an air conditioner was once considered a sign of luxury, but now is a thing of common practice. Many urban homes are equipped with air conditioners in one or more rooms. But everyone who owns an air conditioner knows that it comes at the cost of increasing electricity bills. Although cooling does take a lot of electricity but taking effective steps can surely get it down. One of the main things that can help is maintaining the right temperature for the air conditioners.

How does an air conditioner work?

For most people, air conditioner just throws cool air at the temperature one sets it at. But does it really work that way? In fact air conditioner during cooling process, takes the indoor air, cools it  by passing it through evaporator coil and throws it back in the room. It is quite opposite to how our good old air coolers used to work. Air coolers used to take outside air, cool it with water and throw it in. But air conditioners just work on internal air.

How does the thermostat work?

If you set the thermostat at 64.5oF, does it mean that the air conditioner will cool the room faster than if set at 77oF? No. The thermostat just checks the temperature of the air inside the room and stops the compressor when the temperature reaches the desired level. This means that the compressor will work longer if the temperature is set to a lower level, i.e it will work more and use more electricity if temperature is set to 64.5oF than if it is set to 77oF. This is because it will take less time for air to reach to 77oF than 64.5oF as the compressor is working with the same power or wattage.

What happens when the compressor stops?

The air conditioner just blows the fan when the compressor stops and thermostat reaches the desired temperature level. At this stage the electricity consumption is only for the fan which is running and not for the compressor. The compressor will start again when the thermostat detects that the temperature has increased again from the levels that are set. Compressor is the most electricity consuming component of an air conditioner.

What factors impacts electricity consumption of Air Conditioner?

There are 4 factors that influence the electricity load:

  1. Indoor air temperature
  2. Outdoor temperature
  3. Thermal insulation of the room
  4. Temperature setting of the air conditioner.

If the difference between temperature desired and indoor/outdoor temperature is huge, then the air conditioner will need lot more electricity to cool the indoor air to desired temperature as the compressor will run for longer duration. If the temperature is set at 64.5oF and the outdoor temperature is 100oF then the electricity required will be lot more than when thermostat temperature is 75oF and outdoor temperature is 100oF. As per study by ACEEE (American Council of Energy Efficiency Economy), increase of each oF can save 3-5% of units consumed. This can considerably bring down the units consumed per month in the electricity bill.

What is the ideal temperature that should be set on thermostat?

Having said that, increase in temperature does not reduce the comfort level. In fact as per ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers), the ideal temperature for thermal comfort is between 74.3oF and 78oF in summers (depends on several factors as listed on wikipedia). Thus setting the temperature to 75.2oF saves on electricity bill and provides good comfort. Using ceiling fans along with air conditioners can additionally help in increasing the thermostat temperature.

Does “Quick Cool” option in Air Conditioners help?

Setting an air conditioner to quick cool sets it’s temperature to 64.4oF or 60.8oF . This means that the compressor stops only when indoor temperature reaches this level. But while coming down from 95oF or 104oF it would have surely crossed 75.2oF which is a comfortable temperature. So using “Quick Cool” option does not help because more electricity is used to get the temperature down to 64.5oF whereas compressor would have stopped in between if the temperature was set to75.2oF thereby consuming less electricity.

How do old air conditioners without thermostat work?

Old air conditioners without thermostat have high, medium and low cool options. As we learned earlier that compressors of air conditioners work in binary mode (either they are on or off), an air conditioner without thermostat does not control air temperature. The high, medium and low options just changes the air conditioner fan speed. High means that air conditioner will throw more air and low means that the fan speed will be slow.



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