Pump efficiency refers to how effectively a pump converts input energy into hydraulic energy. It is usually expressed as a percentage, calculated by comparing the pump's output power to its input power. A higher efficiency means that more of the energy used is converted into useful work, while lower efficiency indicates energy losses, often due to friction or turbulence. Factors affecting pump efficiency include design, operating conditions, and the type of fluid being pumped. For example, centrifugal pumps typically have different efficiency ratings compared to positive displacement pumps. Understanding pump efficiency is crucial for optimizing performance and reducing energy costs in various applications.