Abstract
This paper presents an evaluation of technical efficiency and time-dependent changes in productivity of Polish professional electric power and heat & electric power stations by using Data Envelopment Analysis non-parametric method. The research covered the enterprises whose total available electric power amounted to about 98% of that of all professional thermal electric power stations in this country. The analysis has concerned the years 2000÷2004. Impact was considered of such factors as: scale of enterprise activity, form of ownership as well as type of carried out activity, on technical efficiency and time-dependent productivity changes. Changes in productivity of the power generation sector were determined by means of Malmquist index.