The work performed by a pump is a function of the total head and the weight of the liquid pumped in a given time period. Pump input or brake power (BkW) is the actual horsepower delivered to the pump shaft. Pump output or hydraulic or pump power (PkW) is the liquid horsepower delivered by the pump. These two terms are defined by the following formulas.
The power delivered to the pump can also be determined by taking the product of the motor output current and voltage.
The brake horsepower or input to a pump is greater than the hydraulic horsepower or output due to the mechanical and hydraulic losses incurred in the pump. Therefore the pump efficiency is the ratio of these two values.