The estimation is based on the power consumption of the Intelliflo vs the other whisperflo pump. The intelliflo shows the actual flow and wattage used to achieve that flow. Math is 60 GPM on Intelliflo takes 1445 watts per hr. and it takes approx 11 hours to turn the 40K gal pool over 1 time per day. The same flow on a 1 hp whisper flow would use 5 amps per hr.
Another simple way to calculate the cost would be the below program
http://www.pentairpool.com/pool_pump_calc/index.htm
Just find out what your cost per watt is from your power company and calculate the cost / savings.