Program evaluation has become a central issue in the world of utility integrated resource planning. The DSM programs that utilities were operating to meet federal requirements or to improve customer relations are now becoming big business. DSM is being considered an important resource in a utility`s portfolio of options. In the last five years, the amount of money that utilities have invested in DSM has grown exponentially in most regulatory jurisdictions. Market analysts are now talking about DSM being a $30 billion industry by the end of the decade. If the large volume of DSM-program investments was not enough to highlight the importance of evaluation, then the introduction of regulatory incentives has really focused the spotlight. This handbook was developed through a process that involved many of those people who represent the diverse constituencies of DSM-program evaluation. We have come to recognize the many technical disciplines that must be employed to evaluate DSM programs. An analysis might start out based on the principles of utility load research to find out what happened, but a combination of engineering and statistical methods must be used to ``triangulate`` an estimate of what would have happened without the program. The difference, of course, ismore » that elusive but prized result of evaluation: what happened as the direct result of the DSM program. Technical performance of DSM measures is not the sole determinant of the answer, either. We also recognize the importance of such behavioral attributes of DSM as persistence and free ridership. Finally, DSM evaluation is meaningless without attention to planning an approach, communicating results to relevant decision-makers, and focusing as much on the process as the impacts of the program. These topics are all covered in this handbook.« less