District heating systems can play key roles in the energy transition. The transition to a production mix based on renewable intermittent generation will create a larger need for ancillary services including frequency-regulation services. District heating systems typically participate in the wholesale electricity market (the so-called day-ahead market) today but do not, in general, participate in ancillary service markets. Previous studies have shown that it is technically possible to participate in these markets and that district heating systems have a role to play in these markets in the future. This requires investigating how further integration of district heating systems with the electrical grids and markets will impact operation and planning of these units. In addition, while it may be beneficial on a system level for district heating systems to participate in ancillary service markets, district heating system owners and operators will only do so if there are economic incentives to do so. The SeCoHeat project has therefore explored topics related to the profitability for individual district heating systems to participate in other electricity markets than just the day-ahead market, such as ancillary service markets. Studying sector coupling between the heat and electricity systems requires a thorough understanding of both sectors. This project has contributed to this by bringing together experts from both sides which has led to fruitful knowledge exchanges. Furthermore, some deliverables from the SeCoHeat project have been especially written to provide introduction about the heat sector to experts from the electricity sector, and vice versa. This includes an overview of the electricity markets in which district heating systems can participate, the technical requirements to participate in these markets and explanations about how profitability of participating in these markets can be computed. This also includes explanations about how the flexibility on the heat side can be sourced and provided to the electricity system and what limits this flexibility. Another important contribution of this project is the development of a Python-based open model for scheduling district system units on an hourly basis to minimize heat and electricity production costs while maximising revenues from several electricity markets. This model has been used in this project to evaluate the additional profits of participating in ancillary service markets. The results show that substantial additional profits can be made by doing so, both in historical years and in scenarios for future years. This report is a guide to the separate deliverables produced within this project. It offers an overview of the goals, methods and results from the project. The interested reader is referred to detailed descriptions in the corresponding deliverables. The SeCoHeat project was funded by Göteborg Energi AB:s stiftelse för forskning och utveckling. The work has been performed by RISE with the support of reference group members from Göteborg Energi, Vattenfall, Svenska kraftnät, IVL Svenska Miljöinstitutet, Chalmers and Profu.