Ten years after Roberts's (1986) study of electric power procurement a
nd delivery utilities, they have evolved into significant players in t
he industry restructuring debate. This study uncovers new evidence on
cost efficiency, and provides evidence on the separability of the stag
es of production. Analysis of 1977 to 1992 data shows increasing cost
efficiency in delivering power to a given customer base. However, the
costs of network expansion offset these savings. Tests of the ability
to analyze the production stages of vertically integrated firms show t
hat although separability is rejected, it appears that they are evolvi
ng separate technologies.