For a 4 pole small motor of 2 hp operating at 50 Hz:
IE1 efficiency is 77.2%
IE2 efficiency is 82.8%
IE3 efficiency is 85.3%
For bigger ones, 2 pole 200 kW operating at 50 Hz:
IE2 efficiency is 95.3%
IE3 efficiency is 95.8%
Payback period will depend upon the running hours and cost of electricity. Energy represents more than 97 percent of total motor operating costs over the motor’s lifetime.