Non inverter type air conditioner are lossy and inefficient because they start on and off numerous times which can be made inverter type so that the motor of the compressor run smoothly at lower speed. It has been said that upto 60 % energy can be saved, as i m searching to find the feasible option, if anyone has the idea how to convert that old one to Inverter type.

 

If the compressor is a sealed unit, there is most likely no cheap way to do it. The motors are different.
I feel the chrapest way will be to replace the system with a new one.

 

The whole concept of the variable speed air conditioner is only valid when the unit is oversized for the application, so that it needs to run at reduced capacity so as to only provide the cooling needed. The only advantage is that there is less temperature variation.
So the claimed power savings of a correctly sized system are much more from a more efficient compressor and fan than from the variable speed function.
Of course none of the sales people or the advertising will ever mention that. In addition, adding a reliable variable speed drive to an existing AC system will cost more than a replacement.