Energy use intensity (EUI) is a significant index for energy management in the building sector; however, previous research that determined an EUI benchmark for a type of building resulted in serious problems. Such earlier EUI benchmarks cannot fairly evaluate office buildings with different proportions of parking areas and different numbers of floors, becoming an obstacle for energy management. Therefore, this study proposes an area-weighted office building EUI benchmark that calculates according to office areas and parking areas. This study subsequently surveys the electricity consumption of 58 office buildings in Taiwan to determine the office area EUI benchmark that depends on the number of floors in a building, and suggests a reasonable parking area EUI benchmark. Finally, this study promotes a fairer EUI benchmark and ranking system for office buildings in Taiwan. Such a benchmark and ranking system act as a reference for the promotion of the building energy certificate system in Taiwan.