This paper is concerned with the estimation of total factor productivity (TFP) growth for the Iranian electric utilities during the period ۱۹۸۰-۱۹۹۳ on the basis of panel data. A translog cost function is used which accommodates firm - specific variability through a one - way error component model. The results show that the Iranian electricity supply industry experienced increasing returns to scale (IRS) during the period ۱۹۸۰-۹۳, a high rate of technical change and total factor productivity growth during this period. Factor bias of technical change shows that the electricity supply industry has been labor and fuel saving.