Over the past 5 years, Dubin-Bloome Associates (DBA) and Ross & Baruzzini, Inc. (R&B) have jointly been working on a project to determine the relationship of the air conditioning load caused by building lighting with time. Our effort has been funded by the Electric Power Research Institute. An initial literature search determined that the basis of existing calculation methods was data generated by Mitalas in the 1950's for a very limited set of experiments. DBA and R&B then embarked on an experimental program with National Institute of Standards and Technology (formerly National Bureau of Standards) to more fully investigate variables which might effect the load vs time relationship in present-day buildings. NIST has been funded by The Department of Energy (DOE) for their portion of this effort. This paper presents simulation results calculated by several programs, DOE 2, BLAST, Carrier's HAP and Trane's TRACE and MicroAXCESS. These are compared with test results generated by NIST. A discussion of the simulation techniques and the variables which affect the simulation results is included for each of the programs. The simulations show that four of the programs track the experimental results very closely. However, three of these programs use the weighting factor method developed by Mitalas. This method is not well suited to simulation of the demand reduction strategies proposed.