This paper argues that effective competition in reformed wholesale electricity markets can only be achieved if the following six prerequisites are met: (1) separation of the grid from generation and supply, (2) wholesale price deregulation; (3) sufficient transmission capacity for a competitive market and non-discriminating grid access; (4) excess generation capacity developed by a large number of competing generators; (5) an equilibrium relationship between short-term spot markets and the long-term financial instruments that marketers use to manage spot-market price volatility; (6) an essentially hands-off government policy that encompasses reduced oversight and privatization. The absence of any one of the first five conditions may result in an oligopoly or monopoly market whose economic performance does not meet the efficiency standards of a competently managed regulated electrical utility. (C) 2005 Elsevier Ltd. All rights reserved.