Quantifying the electric service panel capacities of California's residential buildings

This study seeks to quantify the size distribution of existing installed electrical service panels within California's residential buildings, a potentially significant barrier to future decarbonization efforts. A large sample of historical building permit data was collected for municipalities throughout the state, from which permitted panel upgrades were extracted and analyzed. These data were used to develop a method for estimating panel capacities that incorporates information about historical code requirements for panel sizing in new construction with a statewide database of parcel-level building attributes. Overall, we find that 3% of single-family (SF) and 10% of multi-family (MF) properties in California have panels in the smallest size range, which will most likely require upgrades. However, 32% of SF and 59% of MF properties have panels of intermediate size, which will likely require the addition of load management systems to support comprehensive electrification. Future panel upgrade needs are expected to be more acute within disadvantaged communities, where the proportion of SF homes with the smallest-sized panels is 4x that in more affluent neighborhoods. We discuss the implications of these and other results within the context of existing and planned future state policies related to residential electrification.