The aim of this article was to determine the energetic effect of use buildings and a district heating network as thermal energy storages to compensate the reduced heat output of the district heating system. Moreover, another so far underestimated values were analyzed, like the effect of the incidence of external temperature and duration of episodes with the lowest external temperatures on the heat output of the district heating system based on 63 heating seasons. Obtained results were presented for the reference district heating system in Poland. According to the results, an average daily external temperature below -15 degrees C occurred once per heating season and temperatures below -20 degrees C occurred only once in four heating seasons. The analysis shows that a temperature of -18 degrees C can be adopted as the reference to determine the expected heat output in the DHS. On this basis the heat output can be reduced for central heating by 1%. The energetic effect of use buildings and a district heating network as thermal energy storages to compensate the reduced heat output of the district heating system was 16.2 MW. The achieved equivalent heat output was 93.2 MW. Considering all solutions, the heat output can be reduced for central heating by 14.8%. (C) 2018 Elsevier B.V. All rights reserved.