Approximately 10%-40% of the energy can be saved, if the occupants' presence/absence is factored into the building operation based on a dozen different case studies conducted in commercial buildings. Two campus buildings, CB1 with 0.3 kW/person and CB2 with 0.2 kW/person, as well as one additional office building, OB1 with 1.0 kW/person, served as data collection sites for occupancy rates and electricity consumption. The analysis results showed that both the total electricity consumption (R-2 = 50%-80%) and plug loads (R-2 = 70%-80%) are significantly correlated with the occupancy rates in the studied buildings. This study also found that the impact of occupants on the building electricity consumption is directly proportional to the building area usage distribution. This finding enabled development of a linear equation to estimate the normalized occupants' impact on the electricity consumption in kW/person. For a third campus building, CB3, used as a demonstration building, the electricity consumption calculated with the previously calibrated linear equation predicted the kW/person to Within 7% of the actual measured 0.53 kW/person. The electricity consumption per occupant represents an appropriate and generalizable measure of the occupants' impacts on the building electricity consumption defined by the building area usage type. (C) 2016 Elsevier B.V. All rights reserved.