Heat pumps versus combined heat and power production as CO2 reduction measures in Finland

• In life cycle analyses, too high CO2 emissions are usually used for CHP heat.
• Seasonal variation should be considered in life cycle assessment of heating options.
• CHP is more efficient in terms of CO2 reduction than heat pumps in most future scenarios.
• Only with very ambitious climate policy, heat pumps may be a better solution.

Heat pumps have rapidly gained popularity in the Nordic area, as they are marketed to provide considerable monetary savings and CO2 emission reductions. Heat pumps are installed even in buildings heated by CHP (combined heat and power production). In this paper we calculate CO2 emission factors of DH (district heating) from CHP and GSHP (ground source heat pumps) in Finland, based on hourly data at present and in various future scenarios. In LCA (life cycle assessment) analyses, usually only annual averages are used. We show that including seasonal variation can result in very different emission factors. Since during warm seasons, electricity production is significantly less carbon-intensive than in cold seasons. We find that the current emission factor of CHP DH consumption change is only 70–100 g/kWh. In the future it is 0…300 g/kWh, depending on the CO2 intensity of electricity production. The similar GSHP emission factor would develop from the present 200 g/kWh to 50…200 g/kWh. As long as electricity consumption has seasonal variation or coal condensing power is significant in the interconnected network, CHP has lower emissions than GSHP. We recommend using CLCA (consequential LCA) methodology and the inclusion of seasonal variation in heating option comparisons.