A 5 star normal AC is the most efficient normal AC, but it cannot be as efficient as an inverter AC, because the inverter AC works on a totally different principle. Also inverter ACs have no star rating as yet in India.
The regular AC compressor has only one speed and the cooling is controlled by offing the AC compressor when a set cold temperature has been reached and then restarting the AC compressor when the room heats up and reaches a set temperature. For example, if you set the thermostat in the regular AC to cool the room to 22 degrees, then the AC compressor starts when the room temperature is 24 degrees and stops when the room has cooled to 20 degrees. This is the cycle that repeats itself throughout the period that the AC is on. This is a very inefficient way of the compressor working. The problems with this arrangement are as follows:
- When a compressor is running at its full speed it is very inefficient. The relation between efficiency and speed is that efficiency varies inversely as the square of the speed. To put it simply, if the speed is double then the efficiency reduces by a factor of the square of the speed, that is efficiency reduces by 4 times. So, the slower the compressor runs, the more efficient it is.
- Start up current in any motor is very high. When a normal AC is on, the compressor starts and stops several times, minutes apart. This start stop cycle consumes a lot of power and is very inefficient.
- The temperature in the room is not a constant comfortable level. It is varying between a minimum and maximum temperature of several degrees apart, and the room is constantly changing from uncomfortably cold to uncomfortably hot, with the set comfort temperature zone in the middle of these uncomfortable temperature range.
The graph below shows the room temperature of a normal AC compared to inverter AC
Benefits of inverter AC compared to normal AC