System-Wise Reliability Assessment in District Heating Systems: Integrating Technical and Customer-Centric Indices

District Heating Systems (DHSs) are integral to the energy infrastructure of urban areas, particularly in cold-climate countries where reliable and efficient heating is essential for both residential and commercial purposes. As these systems evolve with the advent of 4th and 5th-generation district heating, traditional reliability analysis methods must adapt to address the complexities of modern DHSs. Therefore, utilities require effective assessment approaches to evaluate the system's reliability for planning and optimization applications. In today's context, customer satisfaction is increasingly prioritized, with utilities striving to enhance the reliability of heating supply systems to meet this demand. While reliability indices are widely employed for analyzing the technical reliability of DHSs, they often fall short in assessing the system's impact on consumers. This paper examines the characteristics of various reliability indices used in system-wise assessments, highlighting the difference between the reliability of heating systems and other energy sectors. Additionally, it introduces new indices designed to evaluate DHS reliability with a focus on consumer-centric aspects. The indices have been used in an illustrative example. The analysis of results demonstrates that the proposed indices effectively assess the customer-centric reliability in different simulated scenarios compared with other system-wise reliability indices. The proposed indices can be integrated into planning and maintenance strategies, offering a more comprehensive approach to the reliability assessment of modern heating systems.