Current trends in the energy sector are related to energy transformation, the share of renewable energy sources, energy efficiency, security and continuity of supply. As a result of the events of recent years, resilience, i.e. the ability to resist disruptions, has become more critical. The article aims to attempt to formulate the assumptions of a resilient energy system and to illustrate the approach of the example of the heating system. The proposed approach presents resilience in three dimensions: structural, diversification and redundancy. In strategic planning, when decisions with long-term effects need to be made, in-depth analyses of development scenarios are performed, reflecting forecasted trends and threats. The research part of the article presents the results of simulation scenarios for the years 2020-2050, modelled using the OSeMOSYS system. The results allowed for comparison of changes in technology, CO2 emissions, and the investment outlays of the analysed heating system. The justification for undertaking research using the modelling method is the benefits of analytical work. By nature, they are not expensive and enable the definition of a wide range of tests and interpretation of results. The proposed framework of assumptions of a resilient energy system may be helpful for analytical studies of the sector and enterprises. It was assumed that it considers three dimensions: structural – technological and organizational; diversification – which concerns the diversification of fuel supplies and technologies used; redundancy – which involves fuel and technology reserves.