The Commercial Buildings Energy Consumption Survey (CBECS)

The Commercial Buildings Energy Consumption Survey (CBECS) is a national sample survey that collects information on the stock of U.S. commercial buildings, their energy-related building characteristics, and their energy consumption and expenditures. Commercial buildings include all buildings in which at least half of the floorspace is used for a purpose that is not residential, industrial, or agricultural, so they include building types that might not traditionally be considered "commercial," such as schools, correctional institutions, and buildings used for religious worship. See below for some interesting breakdowns and statistics.

Overview of Commercial Building Sector
http://www.eia.doe.gov/emeu/cbecs/cbecs2003/overview3.html 

http://www.eia.doe.gov/emeu/aer/pdf/pages/sec2_4.pdf 

DOE Buildings Energy Data Book
http://buildingsdatabook.eren.doe.gov/ 

Commercial energy consumption intensity by building type
http://buildingsdatabook.eren.doe.gov/TableView.aspx?table=3.1.10