Understanding household peak electricity demand is critical to evaluate the technical need for
electrical infrastructure upgrades. This study characterizes peak loads for existing and new
equipment using metered data from a convenience sample of 11,940 U.S. dwellings from four
sources, including 911 from two sources with end-use metering. After standardized data cleaning
and labeling, we derived descriptive statistics for key metrics, such as maximum demand and
demand factors, and developed predictive models relating 60- to 15-minute demand for the
National Electrical Code (NEC). Mean 15-minute maximum demand was 9.7 kW (median 9.0
kW; IQR 7.0-11.5 kW, 95% CI 9.6 - 9.8 kW), indicating spare capacity in 98% of homes with
hypothetical 100A panels. Maximum demand increased with floor area and number of high-
demand loads. Dwelling maximum demand was driven by higher-power, longer-duration heating
appliances and vehicle charging, while most user-operated appliances contributed little. Demand
factors are used to account for how most devices contribute less than their rated power to
maximum demand. Existing load mean demand factors (28%; median 10%; IQR 0-58%; CI 28-
29%) were higher than those for new loads (21%; median 7%; IQR 0-35%; CI 20-21%), because
new loads changed the timing and magnitude of maximum demand. New high-demand loads had
higher than average demand factors (40-60%). Whole dwelling demand factors support the
NEC’s 40% assumption, but they challenge its conservative 100% treatment of new HVAC. We
propose a data-driven 50% demand factor for new equipment, which would align with metered
data, improve affordability, and modernize electrical codes.