Goal of this project was to assess different approaches of modelling the electricity mix used in the phase of operation of buildings and to offer electricity mix LCI datasets for the different approaches and applications. Building specific mixes and a Swiss national mix were established, matching the generic electricity load profiles of residential and office buildings and of Switzerland (in 60 minutes intervals) with the corresponding hourly production and trade profiles of Switzerland in 2018 and integrating them to seasonal and a yearly electricity mixes. Additionally, electricity mixes based on guarantees of origin as well as future average and longterm marginal electricity mixes were established. The different electricity mixes were applied on the life cycle assessment of a residential and an office building. Besides the standard consumption profile, scenarios with PV self production, battery storage and electric car charging stations were additionally defined for the residential building.

The environmental impacts caused by the two building-specific and the Swiss national mixes are very similar. All mixes show a clear seasonal variation with substantially lower specific environmental impacts in the summer period. Their environmental impacts are substantially higher than those of the Swiss electricity mixes based on guarantees of origin and of the average future electricity mix. The installation of PV and of battery systems result in higher specific environmental impacts of the remaining electricity delivered by the grid but to overall lower environmental impacts of the residential building. The environmental impacts caused by the construction and end of life of the buildings contribute half and more to the life cycle based environmental impacts of the buildings analysed.

It is recommended to use the Swiss na­tional electricity mix based on physical production and commercial trade in buildings LCA and to use the long-term marginal electricity mix in scenario analyses of investments in new buildings and particularly in refurbishment projects with comparatively low energy efficiency. The average future electricity mix may be suited in assessments according to SIA 2040.

The report can be downloaded here.