Limited non-renewable resources and growing problems related to the protection of the environment are main reasons why renewable energy sources are used more and more. This paper presents compared technical and economic analyse of two renewable energy resources, biomass and waste water, for sanitary hot water preparation (DHW). Waste water (sewage) is a source of energy which can be used for heating and cooling buildings with heat pumps. The average waste water temperature such as found in restaurants, laundries, dormitories and etc. varies in the range of 20–40 °C through the whole year. The technology is simple and proven. Biomass as a renewable source of energy has the potential to offer a cost-effective and low carbon alternative to fossil fuels. It is considered as the renewable energy source with the highest potential to contribute to the energy needs of modern society for both the industrialized and developing countries worldwide. Renewable technologies are considered as clean sources of energy and optimal use of these resources are sustainable based on current and future economic and social needs. Compared analyse of the systems is applied for public institution „Home for male children and youth with disabilities“ Prijedor, Bosnia and Herzegovina. Currently, this institution use light fuel oil and elektricity for their energy needs. The aim of this paper is to provide specific information about technology, economics and potential savings.