A system dynamics modeling approach was used to analyze the impact of economical mechanisms on CO2 emissions from the Latvian district heating system that is not covered by the European Union (EU) Emission Trading System (non-ETS). Three policy instruments were included in the system dynamic model: carbon tax, subsidies for solar technologies, and funding for energy-efficient building renovations with the aim to decrease energy consumption. Eight development scenarios were examined, taking into account different policy mixes for the transition of the heat network to the low-temperature regime. The heat tariff was used as the main indicator to determine the pace and structure of the technology change. The existing natural gas technologies and three renewable energy technologies (biomass combustion equipment, heat pump, and solar collectors with accumulation) were included in the model. Modeling results show substantial CO2 reduction potential; however, the results are highly dependent on the applied financial instruments. It is recommended to apply a policy mix, including all the proposed policy instruments—carbon tax, subsidies for solar technologies, and funding for energy-efficient renovation.