The main pipes in water distribution systems have, in many cases, an excess of static pressure. This excess of pressure is usually dissipated by means of intermediate reservoirs, pressure-reducing valves or any other device that produces the required energy loss with the aim to adjust the pressure level to the demand pattern of the system. This hydraulic energy can be used to directly drive a mechanical system or to generate electric power. In this type of recovery energy systems, the available hydraulic power is lower than 100 kW (micro-hydro). In this range, the utilization of conventional hydraulic turbines is not economically viable in short-medium time. In micro-hydropower applications the use of standard centrifugal pumps operated in reverse mode as hydraulic turbines (PAT) can be competitive. In this work, several prediction methods and algorithms suggested by different authors were analyzed and compared. Two case study, in the water system distribution of Murcia and Elche are also presented.