Planning for a Low Carbon Future? Comparing Heat Pumps and Cogeneration as the Energy System Options for a New Residential Area

The purpose of this paper is to compare, from an urban planning perspective, the choice between combined heat and power (CHP) and a ground-source heat pump (HP) as the energy systems of a new residential area in the light of the uncertainty related to the assessments. There has been a strong push globally for CHP due to its climate mitigation potential compared to separate production, and consequently it is often prioritized in planning without questioning. However, the uncertainties in assessing the emissions from CHP and alternative options in a certain planning situation make it very difficult to give robust decision guidelines. In addition, even the order of magnitude of the climate impact of a certain plan is actually difficult to assess robustly. With a case study of the new residential development of Härmälänranta in Tampere, Finland, we show how strongly the uncertainties related to (1) utilizing average or marginal electricity as the reference; (2) assigning emissions intensities for the production; and (3) allocating the emissions from CHP to heat and electricity affect the results and lead to varying decision guidelines. We also depict how a rather rarely utilized method in assigning the emissions from CHP is the most robust for planning support.