Electricity Saving Tips For Homes And Offices

Ideal Air Conditioner temperature for electricity savings

By on July 29, 2015

Hindi Translation: बिजली बचत के लिए आदर्श एयर कंडीशनर तापमान

Buying an air conditioner once considered a sign of luxury, is now becoming quite common in India. 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.

Air Conditioner Temperature

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 18oC (64.5oF), does it mean that the air conditioner will cool the room faster than if set at 25o(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 18oC (64.5oF) than if it is set to 25oC (77oF). This is because it will take less time for air to reach to 25oC (77oF) than 18oC (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 18oC (64.5oF) and the outdoor temperature is 38oC (100oF) then the electricity required will be lot more than when thermostat temperature is 24oC (75oF) and outdoor temperature is 38oC (100oF). As per study by ACEEE (American Council of Energy Efficiency Economy), increase of each oC 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 23.5oC (74.3oF) and 25.5oC (78oF) in summers (depends on several factors as listed on wikipedia). Thus setting the temperature to 24oC (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.Air Conditioner Temperature Infographic

Does “Quick Cool” option in Air Conditioners help?

Setting an air conditioner to quick cool sets it’s temperature to 18 or 16 oC (64.4oF or 60.8oF. This means that the compressor stops only when indoor temperature reaches this level. But while coming down from 35 or 40 oC (95oF or 104oF) it would have surely crossed 24oC (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 18oC (64.5oF) whereas compressor would have stopped in between if the temperature was set to 24oC (75.2oF) 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 learnt 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. The options do not change the temperature of the room, nor do they change the electricity consumption.

Here is a short video for tips to reduce power consumption of air conditioner in India

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262 Comments on "Ideal Air Conditioner temperature for electricity savings"

If you have any question or comment, please leave a message here. We try to reply to questions in the sequence they come in. We work from Monday-Friday 10AM-7PM. If we know the answer we try to reply to the question within 3 days.

July 14, 2015

Hi, Recently we are using AC 1.5 ton 3 star since long time on fixed 28 degree in auto mode & earlier my Bill was max to max reach to Rs.2500-3000 but in last Month, my bill been increased drastically in very high side of Rs.9754 in same usage of AC or other Appliances in same mode. Pls. suggest on this urgently.

July 13, 2015

I have raised 3 questions but i do not find any one on my next day of browsing this site. What has happened to those

July 10, 2015

i live in Kolkata.
ac model:ah-xp13pmt 1.1 ton inverter SHARP.(it does not have heating function,it has only cooling capability).

my questions are:
1:let’s say the outside temp is 21c and i set the thermostat at 28c normal cooling mode,then will the compressor still run?or just the fans?

2:it’s rainy season,and let’s face it,it’s acid rain.so i am worried about my outdoor unit being deteriorated.
is there some ways i can maintain that?for eg:by washing it with pure water or something like that?


Vidit mehta
July 6, 2015

Hi I have bought 1.5 tonsplit ac for a 250 sq ft room of Hitachi company but since installation my usage has been for night times only but now my normal electricity bill has gone up to 3000 which earlier use to be 800 rs. Kindly guide me with ideal mode for usage and temp. To be set so I can save on my bill amount. I live in mumbai. I noramly keep temp at 21 degrees and keep it on auto mode.

July 2, 2015

Hi BB team ,
I have a room of size = 12X21=252 sq. ft on first floor cieling is exposed to Sun. I was told to purchase a split Ac of 2 ton and not a window AC of 2 ton by a technician of AC. When I asked the technician of why not purchase a 2 ton window AC when it is lesser in price ,easy to install , Power Consumption is nearly Same and moreover the btu Cooling of both window n split is same.
He told that in 2 ton split AC the condensor coils are large and the gas Condensation is easily done in large coils so the cooling is very fine.
Whereas in a 2 ton Window AC the condensation Coils are small and the gas is not condensed easily so in 2 ton Window the Cooling fails.
Please give correct advice on whether to purchase a split unit or a Window unit of 2 ton ?

Sathish kumar
June 30, 2015

I am using Blue Start A/C 1.5 ton, 5 star. My room size is 14/14. I am using the ac at 30. Will it consume more power.

christopher Foo
June 28, 2015

How to maintain office room temperature at 24 degree celcius of 600 sq ft? How many hp aircon needed?

June 18, 2015

Sir, i live in top floor in delhi. My landlords have given me an AC but have disabled the power save mode(obviously). The meter is also there. How do I minimize the meter reading? The meter runs faster than usain bolt. :|

Tapas Roy
June 15, 2015

I have purchase a 1.5 ton AC, make carrier. 3 star. My house size is 12’x 12′. I leave at west bengal. I have to run my ac for 4-5 hours per day (maximum) only for summer session. Is my decision right or otherwise. Please answer me.

June 14, 2015

Sir,I bought blue star 1 ton 5 star split ac…at starting it works fine but now when I turn off the ac by remote..a cracking sound come from the indoor unit like internal body is broking but when I turn off by main switch..its okkk.no sound coming…is there problem or not…and one more thing that left side of air wing not blow air properly….i have clean the filter but air not coming properly from the left side of the wing…what’s the problem