The paper presents an analysis of several variants of energy-efficient solutions for hot water supply systems in Minsk buildings that ensure significant reduction of energy for hot water supply in comparison with the existing level. The different systems have been considered as technical facilities for usage of solar energy and secondary heat sources and which are based on heat recovery of “grey” waste water, solar collector, photoelectric transducer, heat pump. Comparative analysis of the considered variants shows economic efficiency of waste water heat utilizers. An advantage of such system is in its all-year round usage in comparison with a solar collector. The second variant that is a combination of waste water heat utilizer and a solar collector that increases energy saving but it requires the increase of capital expenses. The third variant completely covers expenses of heat energy which is necessary for hot water supply. It is neces-sary to attract attention to the fact that expenses in the first two variants are close to the required ones but values of the third variant may significantly exceed the reliable level. The paper contains analytical material of Belarusian and Vietnamese researchers who were actively involved in implementation of the joint Belarusian-Vietnamese project “Usage of Renewable Power Sources in Physical-Mathematical Model of Heat Regime of Energy-Efficient House” (Project code: VAST. HTQT. Belarus. 03/2012–2013).