By examining the actual perfommance of conservation or demand-side man
agement (DSM) programs for ten utilities, Joskow and Marron (1992) hav
e made an important contribution to policy discussions about the wisdo
m of relying on utilities to improve customer energy efficiency. We us
e Joskow and Marron's method to analyze twenty utility commercial ligh
ting programs and, like Joskow and Marron, find wide variations in ind
ustry reporting practices and savings evaluation methods. We extend th
e method by systematically accounting for several of the most importan
t sources of variation and comment on how they influence total program
costs. Our accounting also allows us to relate remaining program cost
variations to the program sizes and the electric supply costs avoided
by the programs. We draw qualified, yet affirmative, conclusions rega
rding the cost effectiveness of the programs.