The transition towards 4th generation district heating systems are widely studied in last years. In this research, the economic reasonability of recovered industrial waste heat usage in the district heating system is investigated. Research is based on a case situation with an actual district heating system and nearby located factory with possible waste heat. This article contains a description and characteristics of selected district heating system and potential waste heat source, the overall methodology for the thermal energy potential and recovery calculations of waste heat flow. Taking into account losses in transmission, 67.5 MWh of heat can be transferred to the heat supply network every month, covering 4–12 % of the system load during the heating season. This would reduce the CO2 emissions from the heating system by 5–10 % monthly.