In the hydropower sector, the weight of electro-mechanical equipment is an important input data. During the design stage, it allows to estimate material cost, to perform Life Cycle Assessments and to consider adequate load factors on the supporting structures. At the end of the lifetime, in case of dismantling or retrofitting, the esti-mation of the equipment weight allows to appraise the material value and to plan the operational activities. However, the engineering knowledge is quite fragmented and limited on this topic, and only a few weight equations are available in the literature. In this contribution, the available equations are firstly reviewed and discussed. Secondly, data were collected both from the literature and from hydropower companies, and gener-alized to provide expeditious equations. The equations presented in this paper allow for a preliminary estimate of the weight of: 1) the runner of Pelton, Kaplan, Bulb, Cross-Flow (Banki type) and Francis turbines, and water wheels; 2) the casing of Pelton and reaction turbines; 3) draft tubes; 4) electric generators. Data on Vortex, Turgo and Hydrokinetic turbines, Archimedes screws and guide vanes are presented. The opportunities associated to innovative and lighter construction materials are discussed.