Limited availability of fossil fuels and various issues connected with environment conservation lead to a growing interest in unconventional sources of energy. The latter include wastewater carried via sewage systems. Yet, the possibility to extract thermal energy from this source depends on a number of factors, location of heat recovery system being one of them. Viability of utilizing raw wastewater and effluent discharged to a receiving body after treatment process, as potential sources of energy, was assessed using SWOT/TOWS analysis. Strategies for developing systems of heat recovery from both types of wastewater have been defined, and recommendations related to their use in Poland have been formulated.