In this work, the concept 'city water heating' is introduced. It consists in bringing a significant amount of residual thermal energy (waste heat) from a power plant to a city by means of heating the potable water supplied to this city. For this purpose (i) a great amount of the city water has to be supplied through a single aqueduct, (ii) the aqueduct has to pass near the power station, and (iii) the water supplied to the city has to be colder than the cooling circuit water in the power plant. The hot water generated in the power plant cooling circuit (which is usually dissipated in the cooling tower) is conducted through a pipe to a place near the aqueduct and, by means of a heat exchanger, part of the cooling water heat is then transferred to the colder potable water supplied to the city. This has the great advantage of using the existing city water network itself to transport the heat to the houses. Based on data from a coal power plant located in Asturias (Northern Spain), two city water heating systems of different sizes are described and analysed. The following advantages were found: (i) energy saving and cost reduction for inhabitants, (ii) reduction in global warming and (iii) CO2 emissions reduction. (C) 2015 Elsevier Ltd. All rights reserved.