Power consumption of AC

Power consumption of Air Conditioner calculation is easy

Power consumption of Air Conditioner (AC) depends on lots of factors like the room size, insulation, number of windows and doors, window or split AC, period of usage, the make and model of the air-conditioner, as well as its EER (energy Efficiency Rate). AC's have a temperature control mechanism (thermostat), by this AC can turns on and off to keep the temperature which you set before. However i am trying to give you a simple thumb rule by which you can estimate the power consumption of AC and i do not guaranty you the result will 100% accurate.
Some simple term and calculation for calculating power consumption of Air Conditioner
One Ton of Refrigeration or air conditioning means it can removes the amount of heat needed to melt one ton of ice in 24 hours. One Ton of Refrigeration can remove 12,000 B.T.U.'s of heat in one hour. The B.T.U. is the amount of heat needed to raise 1 pound of pure water from 0 deg Fahrenheit to 1 deg Fahrenheit.
Mathematically

1 Ton = 12,000 B.T.U

and

12000 BTU per hour = 3517 watts per hour.

So, for 2 Ton, AC 24000 btu or 7.33706 kw/h power required.
But in practical scenario is different. 2 Ton AC takes 12 to 14 Amp current normally. Maximum 15A .
We know
Power= current *voltage
= 15*220
=3.3 kw/h
As the same way 1.5 ton AC consumes 5.3 kWatts of power. This figure is right when AC is operating all the time. If it is on only 50% of the time (more likely) then it will use about 2.6 kWatts of power.

another thing power consumption will go up every degree of reduction of the temperature setting of AC, because the percent running time will increase.

AC Power Consumption for 1,1.5 and 2 ton

AC Capacity	Theoretical PowerConsumption	Practical Power Consumption
1 Ton	3.51685 kw/h or 12000 btu	1.335 KW/h
1.5 Ton	5.2752 kw/h or 18000 btu	2.6 kw/h
2 Ton	7.33706 kw/h or 24000 btu	3.3 kw/h

A typical home air conditioning unit from wiki