arXiv:2611.08347v1 Announce Type: new Abstract: Building electrification projections are typically developed at aggregated geographic levels to support bulk power system analysis, even though a significant portion of the infrastructure investments required to accommodate electrification occurs within distribution systems. Existing methodologies to disaggregate load growth projections onto distribution networks are based on context-specific analyses that require detailed data on building electricity consumption, distribution feeders, and geographic parcels, which are often proprietary and unavailable for policy and economic impact studies. This paper presents a methodology to disaggregate county-level building electrification projections onto representative distribution feeders and evaluate their impact on distribution upgrade costs. The proposed approach combines bulk system end-use electrification projections with representative feeder sets to generate building-level electrification measures. These measures are then used to create load profiles that are consistent with county-level projections while preserving the spatial diversity of electrification demand required for distribution infrastructure analysis. Using a case study of Genesee County, in Michigan, the results show that the proposed methodology is able to capture a diversity of feeder-level responses to electrification and represent the different realities that building electrification produces within the distribution system. This allows to represent localized load variations and capture more realistic distribution system upgrade costs driven by electrification.