Let’s start by understanding the basics of air conditioners.

1.Ton: This is the amount of heat that an AC unit can remove in one hour.

2. BTU (British Thermal Unit): This is the measurement of heat.

3. EER (Energy Efficiency Ratio ): This is the ratio of heat extracted per hour to power input in watts.

EER: BTU/hr/Watt

4.ISEER (Indian Seasonal Energy Efficiency Ratio), is a new norm that was established by Bureo of Energy Efficiency for India. It is the ratio of annual heat removal to input energy.

Let’s now take an example of 1.5 tons, 5-star split AC (non-inverter type).

Heat Removal in 1Hr: 12000 BTUX1.5=18000 BTU

1 BTU/Hr = 0.293071 Watts

So 18000 BTU X 0.293071 =5275.278 Watts

The 5 star AC EER is usually 3.5 to 4. This is according to 2016 BEE norms. This means that the input power is 5275.278/3.5 = 1500 watts.

Energy consumption for 8 hours will be 8X1.5 = 12 units

Monthly consumption will be 30X12=360 Units

Electric bill based on 5 Rs/unit = 5X360= Rs 1800

Inverter AC is 20% more efficient than non-inverter AC because of variability in speed and tonnage depending on the heat content of the room. This will result in a lower electric bill. Inverter AC is 20% more efficient than non-inverter AC. Electric bill will be Rs 1800/1.2 = Rs 1500 per month.