Single-speed drives start motors abruptly, subjecting the motor to high torque and current surges up to 10 times the full-load current. Variable frequency drives offer a soft start, gradually ramping up a motor to operating speed. The variable frequency lessens mechanical and electrical stress on the motors and can reduce maintenance and repair costs and extend the motor life. Variable frequency drives also allow more control of processes with water distribution – facilities can consistently maintain desired flowrates by using automated controls. Energy savings from variable-frequency drives can be significant. For example, with a centrifugal pump even a small reduction in motor speed can reduce a pump’s energy use by as much as 50%. For a 25 horsepower motor running 23 hours per day (2 hours at 100% speed; 8 hours at 75%; 8 hours at 67%; and 5 hours at 50%) a variable frequency drive can reduce energy use by 45%. Because benefits vary depending on system variables it’s important to calculate benefits for each application before specifying a variable frequency drive.