This paper evaluates the operational energy performance of a system to produce domestic hot water using waste heat in a centralised air conditioning system in a hotel in Cuba.The hotel facility has two different chillers capacities, where the system recovers the condensed heat through a heat exchanger at the compression process outlet.These schemes allow the simultaneous production of air conditioning and Domestic Hot Water, also those considering thermal storage tanks.The system modelling starts analyzing its components and processes based on the traditional thermodynamics and heat transfer equations and ends with a validation process.This model estimates a wide range of operating conditions, such as the thermal demands of the cooling load, the chiller water temperature, the electricity consumed by chillers, and the climatological variables involved.The system is evaluated in the highest tourism season in Cuba during a year under partial load.Results were validated in a hotel as a study case, which allowed us to estimate the thermal potential available in the plant to meet the thermal demand of the hot water required and show that variations in the chiller operation affect the temperature stability in the hot water system.