This document describes a methodology to evaluate energy efficiency performance of pump units based on a non-dimensional numerical value called Energy Efficiency Index (EEI). This document covers pump units consisting of: - one single or several rotodynamic water pump(s), including where integrated in other products, and driven by a motor system, consisting of an electrical motor, and either: - a terminal box which only enables to operate the pump unit at constant motor stator frequency and thereby (nearly) constant rotational speed, or - a CDM (Complete Drive Module) which enables to operate the pump unit at variable rotational speed depending on a varying demand of flow rate and/or discharge or differential pressure. NOTE A CDM is also often called VSD (Variable Speed Drive). Pump units as defined above are treated as extended products in respect to their energy efficiency.