Many factories are troubled by excessive electricity costs. Direct on-line starting of motors brings large starting current and extra energy waste. This article introduces the energy-saving logic of VFD solutions based on the affinity law. It objectively analyzes which equipment is suitable for frequency conversion renovation, sorts out common misunderstandings of VFD energy saving, and shares positive user reviews of TAGOL VFDs on stability, low-speed torque and convenient debugging, providing practical reference for factories to carry out energy-saving transformation.