Calculate the power consumption of AC & Electricity usage

Its hot inside lets turn on the AC!!

The air conditioner is one of the high power consuming appliances at home. During sunny days you might have noticed a drastic increase in power consumption as well as the utility bill (if you use AC). This article will guide you through the types of Air conditioners, their power consumption of ac and electricity bill calculation.

Online electricity bill calculator for AC

Types of household Air conditioners

Here we will discuss on the following types of air conditioners:

  • Central Air conditioners
  • Split air conditioners
  • Window units

Central air conditioners

Central air conditioners deliver cooled air to the through a system of supply and return ducts. The cooling unit (evaporator, condenser, and compressor) is placed outdoors.

Split air conditioners

Split ac consists of an indoor unit and an outdoor unit. The evaporator unit is placed inside the room and condenser-compressor unit combination is placed outdoors. The coolant is circulated between the indoor and outdoor units using copper pipes.

Window AC

It is the most commonly used type of residential air conditioner. It is a single unit containing the evaporator, condenser and compressors all together. It is fixed in the slot made in the wall or window sill.

Difference between Inverter AC and Non-inverter AC

power consumption of air conditioners

Inverter ACs are becoming much popular in the market today. The key difference between an inverter and non-inverter air conditioner is that an inverter air conditioner is capable of controlling the speed of its compressor motor. Once the required temperature is attained, the speed of the compressor motor is lowered. This can save a lot of energy. But the conventional AC or the non-inverter AC cannot control its speed. It can either run at the full speed or stop to zero. Each time it turns on, it consumes 6-8 times its rated current during start. Also, inverter ACs are less noisy than conventional ones.

difference between an inverter and non-inverter air conditioner
Power fluctuation diagram for Inverter and Non-inverter AC.

Understanding Tonnage of AC

Air conditioning units are rated in tons. One ton is equal to 12,000 Btu per hour (3.517 kW). That is the amount of heat required (288,000 Btu) to melt one ton of ice in a 24-hour period. Therefore 288000, when divided by 24, gives 12000Btu, which is equal to one ton.

Understanding Energy Efficiency Ratio (EER)

The Energy Efficiency Ratio (EER) is the ratio of output cooling energy (in BTU/hr) to input electrical energy (in watts) at a given operating point. EER is normally calculated with a 95 °F (35 °C) outside temperature and a room temperature of 80 °F (26.6 °C) and at a relative humidity of 50%.

EER = (Cooling energy in BTU/ hr) / (Electrical energy consumed in watts)


EER = (Cooling energy in kW/ hr) / (Electrical energy consumed in watts)

*Either of the above formulae can be used based on the local standard.

Understanding Energy Star

Energy Stars indicates the efficiency of the air conditioners. More stars indicate higher energy efficiency. The below table indicates the star ratings and EER of air conditioners.

Number of stars and EER of Split A/C units

Number of starsMinimum EERMaximum EER
1 Star3.103.29
2 Star3.303.49
3 Star3.503.99
4 Star4.004.99
5 Star4.50

Number of stars and EER of window A/C units

Number of starsMinimum EERMaximum EER
1 Star2.52.69
2 Star2.72.8
3 Star2.93.09
4 Star3.13.29
5 Star3.3

Power consumption of AC

Power consumed by split A/C

1 Ton1.5 Ton2 Ton
1 Star1100W1651W2200W
2 Star1036W1554W2071W
3 Star940W1408W1878W
4 Star782W1174W1565W
5 Star781W1172W15623W
Note: All the above are estimated values. The actual power consumption varies slightly.

Power consumed by window A/C

1 Ton1.5 Ton2 Ton
1 Star1355W2032W2710W
2 Star1279W1918W2557W
3 Star1174W1761W2348W
4 Star1100W1650W2200W
5 Star1065W1599W2131W
Note: All the above are estimated values. The actual power consumption varies slightly.

Bill and consumption calculation

From the above table, energy consumption can be calculated as follows:

Lets calculate the power consumed by a 1.5 ton 5 star rated split a/c operated for 10hrs.

Number of Units consumed = (Power consumed in kW) x (Operation Hours)

Power consumed can be noted from the table above or from the brochure or nameplate details of the air conditioner.

Number of Units consumed = (1172/ 1000) kW x 10 hrs

=11.72 units (kWh)

Electricity bill = Number of units consumed x Rate per unit

Online electricity bill calculator for AC

Factors affecting the efficiency of an air conditioner

The following are the major factors affecting the efficiency and performance of an air conditioner and directly impacts the power consumption of air conditioner.

  • SEER Rating
  • Outdoor temperature and temperature set-point (Higher the difference between the outdoor temperature and the set-point, greater will be the power consumption)
  • Technology used (Inverter technology or conventional technology)
  • The number of people and appliances inside the room.

We hope that the above article has fulfilled your requirement and you can calculate the power consumption of air conditioner yourself now.

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