A variety of methods exist for simulating energy usage, which range from simple manual calculations to extensive procedures requiring the use of a mainframe computer. However, there is relatively little readily available data on how the simulation results compare with the actual measured usages. This is particularly true for buildings that are in normal use, with the analyst not having any control over the usage of the building.

In this study, the extensive use of a simplified energy-analysis procedure on existing buildings will be described. Between 1980 and 1983, the energy usages of over 100 buildings, ranging in size from a few hundred square feet to over 14,860 m2 (160,000 ft2), were simulated. The simulated energy usage of 43 of these buildings (representing 292,630 m2 (3,150,000 ft2) will be compared with their historical energy usage.