Comparing the Comparative Efficiency of System Marginal Price and Pay as Bid Auctions in Electricity Markets

System marginal price auction and pay as bid auction are common auctions in electricity markets. The present article discusses the impacts of selecting between different common auctions in electricity markets (system marginal price auction and pay as bid auction) on production efficiency، total efficiency and average expected price in an asymmetric information situation، where each player’s information about the marginal cost of the competitor is incomplete. A model is designed to conduct the comparative study of alternative auction mechanisms. The model is based on two profit maximizing players، with full information about their marginal cost and incomplete information about their competitor. Assumptions which has been used to construct the model are based on Iran’s electricity market structure. The outcome indicates that although production efficiency in alternative auction mechanism do not differ from each other، expected price under system marginal price auction is lower than pay as bid mechanism. Vice versa occurs in total efficiency.