The energy efficiency in the building sector, a widely accepted point inside world energy sustainability, can be pursued in a variety of complementary ways, being energy consumption reduction one of them. Specifically, the residential buildings are responsible for more than 40% of the total energy consumption of the European Union. Therefore, this residential sector is an important target for optimizing the use of energy. This paper examines the energy saving measures for multi -family residential building thermal systems in the city of Granada. The state and usage patterns of such systems in a middle-size city are surveyed and analysed in order to propose sounded saving measures. The proposed measures were quantified according to two parameters: energy saved and CO2 emissions reduction. This quantification enables the identification of best measures either cost or energy effective, concluding that the biggest benefits are obtained adopting solar/biomass energy, while other zero-cost measures like the information campaign have more impact than, for instance, boiler replacement. Finally, it is concluded that an extension of mandatory installation of solar systems to existing buildings should be considered. (C) 2018 Elsevier B.V. All rights reserved.