Open, Reproducible Per-Bidding-Zone Carbon Intensity for Nordic Power Systems

Abstract

Carbon-aware scheduling of electrical loads depends on accurate grid carbon-intensity (CI) signals, yet existing tools commonly apply a uniform placeholder emission factor that misrepresents regional variation. This work presents an open, reproducible method for computing per-bidding-zone CI across the Nordic power system. Generation-by-type data from ENTSO-E is combined with IPCC AR5 life-cycle emission factors, duration-weighted per bidding zone, with an explicit materiality threshold for missing data. Applied to nine bidding zones (NO1-NO5, SE1-SE4) for 2025, the method yields CI values ranging from 14.5 to 39.6 gCO2eq/kWh. The results reveal that the uniform 18.0 gCO2eq/kWh placeholder is wrong in both directions: it understates CI for most zones, by a factor of approximately 2.2 for NO4, yet overstates CI for the nuclear-dominated zone SE3, whose production-based CI is the lowest of the nine. Drift is characterised against a pre-registered threshold of 15% year-on-year change, including a borderline case in SE4 and event-driven variation in NO4. Forecasting experiments do not reject the null hypothesis that simple baselines suffice, in either the Norwegian or Swedish zones. The full method, data, and results are released under open licences and archived at DOI 10.5281/zenodo.21042581, with the per-zone values contributed upstream to the codecarbon library. Per-bidding-zone resolution is necessary for accurate carbon accounting in Nordic grids, where country-level averages obscure substantial intra-country variation.