The efficiency of pumps refers to the ratio of effective power of pumps to shaft power of pumps. η=Pe/P

The power of pumps normally refers to input power, i.e. the power conveying from prime mover to pump shaft, so it is also called shaft power and it is expressed as P.

Effective power means product of pump lift, mass flow rate and gravity acceleration.

Pe=ρg QH (W) or Pe=γQH1000 （KW）
ρ：the density of pump conveying liquids  (kgm3)
γ：the unit weight of pump conveying liquid(N m3)
g: gravity acceleration (ms)
Mass flow rate Qm=ρQ (th or kgs)