A typical older 100 HP motor at full load, continuous operation, cost over $59,000 per year to operate. Using a premium efficiency motor could save you $2,700 each and every year. Calculate the cost of running your motor. If you are running it at least one full shift per year, the cost of electricity  becomes the real expense. The motor cost little compared to the power it uses.

Lab test show that motor efficiency may be reduced by 1% to 2% during motor repair. You might be better off with a new premium efficiency motor. If your motor shop can certify that you motor will be equal to or more than a qualifying premium efficiency motor, then go with the rebuild. If not, purchase a premium efficiency motor and reap the savings in power for years to come.