District heating (DH) is widely used in heating buildings in Europe, while Latvia takes the 2nd place among European countries by percentage of citizens served by district heating (Euroheat & Power, 2016). In Riga, DH heat is produced by several plants – gas and biomass – that are connected in one network. Exhaust gas temperature from DH plants reach 130 °C and is decreased by flue gas condenser by utilizing the wasted heat from the flue gas. The aim of this research is to evaluate the theoretical feasibility of using low-temperature lift heat pumps in the DH system for flue gas condenser efficiency improvement. The study examines connection scheme when a heat pump is installed on heating network's return line before flue gas condenser, so the heat pump can utilize the return line of the DH network as the heat source and forward line as the sink. Six scenarios were evaluated with two different heat pumps. All calculations have been done by using developed for this purpose TRNSYS model and based on real data from Riga biomass heating plant for 2016 and 2017 years. The results show that theoretically heat pump with low-temperature lift can be applied in the district heating systems for flue gas condenser efficiency improvement. It allows decreasing primary energy usage and CO2 emissions, at the same time being cost-effective.