Look for the capacity of the A/C i.e. 1 ton or 1.2 ton or 1.5 ton.
Look for the energy star rating(higher the star rating, lower the power consumption).
Look for the ERR values(higher the ERR values, lower the power consumption is).
Look at the power consumption in watts.
Inverter A/Cs has advantages but the con is that they priced a little bit higher side.
In power consumptions inverter A/Cs consumes very less power compared to conventional A/Cs.
With normal A/Cs there is a little bit of power fluctuation when the compressor starts but this not happens in case of inverter A/Cs.
Look for the decibels value of the A/C(lower the decibel values, quieter the A/C is).
Look at the installation costs also when buying the A/C.
Inverter A/Cs consume 25-30% less power compared to normal A/Cs but its not 50-60% that the companies are claiming.