This article discusses the development of a system for the combined use of solar and water energy based on a systematic approach to power supply. An improved physical model has been developed based on a model for predicting the production of electricity, taking into account the power and time of solar radiation, the amount and speed of water flow. At the same time, the share of electricity in the use of solar and water energy was determined simultaneously, depending on the conditions for the uninterrupted supply of consumers with the daily necessary electricity. The assessment of indicators of the combined use of solar and water energy and the definition of energy efficiency were developed by the authors on the basis of an increase in the share of electricity obtained from renewable energy sources in the electricity supply, which is explained by the coincidence of theoretical and experimental results.