Competitive Bidding Behavior in Uniform-Price Auction Markets

Profit-maximizing bidding in uniform price auction markets involves bidding above marginal cost. It therefore is not surprising that such behavior is observed in electricity markets. Common bidding behavior such as "hockey stick" bids easily are explained by suppliers determining their supply offers to maximize profits. This incentive to bid above marginal cost is not the result of coordinated action among the bidders. Rather, each bidder is independently selecting its bid to maximize profits based on its estimate of the residual demand curve it faces. Profit-maximizing bidding does not mean that "the sky’s the limit." Typically, bidders are limited in how high they want to bid. As prices increase, operators become increasingly concerned that their capacity will not be selected—that someone else will step in front of them in the merit order. Only when (1) demand does not respond to price, and (2) the largest unhedged block of capacity is essential to meet demand can the bidder holding this largest block profitably name any price. In all other cases, the supplier bids a price for its energy capacity to optimize its marginal tradeoff between higher prices and lower quantities. Price response from either demand or other suppliers prevents the supplier from raising its bid too much. Profit maximizing bidding should be expected and encouraged by regulators. It is precisely this profit maximizing behavior that guides the market toward long-run efficient outcomes.Auctions, Electricity Auctions, Market Design

Competitive Bidding Behavior in Uniform-Price Auction Markets

Profit-maximizing bidding in uniform price auction markets involves bidding above marginal cost. It therefore is not surprising that such behavior is observed in electricity markets. This incentive to bid above marginal cost is not the result of coordinated action among the bidders. Rather, each bidder is independently selecting its bid to maximize profits based on its estimate of the residual demand curve it faces. The supplier bids a price for its energy capacity to optimize its marginal tradeoff between higher prices and lower quantities. Price response from either demand or other suppliers prevents the supplier from raising its bid too much. Profit maximizing bidding should be expected and encouraged by regulators. It is precisely this profit maximizing behavior that guides the market toward long-run efficient outcomes.Auctions, Electricity Auctions, Market Design

Equilibrium Predictions in Wholesale Electricity Markets

We review supply function equilibrium models and their predictions on market outcomes in the wholesale electricity auctions. We discuss how observable market characteristics such as capacity constraints, number of power suppliers, load distribution and auction format affect the behavior of suppliers and performance of the market. We specifically focus on the possible market power exerted by pivotal suppliers and the comparison between discriminatory and uniform-price auctions. We also describe capacity investment behavior of electricity producers in the restructured industry.Electricity markets; Supply function equilibrium; Markov perfect equilibrium; electricity auctions; pivotal suppliers; capacity investment.

Competition in Electricity Spot Markets: Economic Theory and International Experience

auctions, electricity markets

An Experimental Study of Complex-Offer Auctions from Wholesale Energy Markets

A Payment Cost Minimization auction has been proposed as an alternative to the Offer Cost Minimization auction for use in wholesale electric power markets with an intention to lower procurement cost of electricity. Efficiency concerns have been raised for this proposal while assuming that the true production costs would be revealed to the auctioneer in a competitive market. Using an experimental approach, the study compares the performance of these two complex-offer auctions, controlling for the level of unilateral market power. The analysis finds that neither auction results in allocations that correspond to the true cost revelation. Two auctions perform similarly in terms of procurement cost and efficiency. Surprisingly, consumer prices in a competitive environment approach the prices of an environment with market power. It appears that the expected institutional effects for procurement cost and efficiency are greatly dominated by the effects of anti-competitive behavior due to the offer complexity and a cyclical nature of market demand

An Experimental Study of Complex-Offer Auctions from Wholesale Energy Markets

A Payment Cost Minimization auction has been proposed as an alternative to the Offer Cost Minimization auction for use in wholesale electric power markets with an intention to lower procurement cost of electricity. Efficiency concerns have been raised for this proposal while assuming that the true production costs would be revealed to the auctioneer in a competitive market. Using an experimental approach, the study compares the performance of these two complex-offer auctions, controlling for the level of unilateral market power. The analysis finds that neither auction results in allocations that correspond to the true cost revelation. Two auctions perform similarly in terms of procurement cost and efficiency. Surprisingly, consumer prices in a competitive environment approach the prices of an environment with market power. It appears that the expected institutional effects for procurement cost and efficiency are greatly dominated by the effects of anti-competitive behavior due to the offer complexity and a cyclical nature of market demand

The Supply Function Equilibrium and Its Policy Implications for Wholesale Electricity Auctions

The supply function equilibrium provides a game-theoretic model of strategic bidding in oligopolistic wholesale electricity auctions. This paper presents an intuitive account of current understanding and shows how welfare losses depend on the number of firms in the market and their asymmetry. Previous results and general recommendations for divisible-good/multi-unit auctions provides guidance on the design of the auction format; setting the reservation price; the rationing rule; and restrictions on the offer curves in wholesale electricity auctions.Wholesale Electricity Markets; Supply Function Equilibria; Competition Policy

Understanding Strategic Bidding in Restructured Electricity Markets: A Case Study of ERCOT

We examine the bidding behavior of firms competing on ERCOT, the hourly electricity balancing market in Texas. We characterize an equilibrium model of bidding into this uniform-price divisible-good auction market. Using detailed firm-level data on bids and marginal costs of generation, we find that firms with large stakes in the market performed close to theoretical benchmarks of static, profit-maximizing bidding derived from our model. However, several smaller firms utilized excessively steep bid schedules that deviated significantly from our theoretical benchmarks, in a manner that could not be empirically accounted for by the presence of technological adjustment costs, transmission constraints, or collusive behavior. Our results suggest that payoff scale matters in firms' willingness and ability to participate in complex, strategic market environments. Finally, although smaller firms moved closer to theoretical bidding benchmarks over time, their bidding patterns contributed to productive inefficiency in this newly restructured market, along with efficiency losses due to the close-to optimal exercise of market power by larger firms.

Cournot versus Supply Functions: What Does the Data tell us?

The liberalization of the electricity sector increases the need for realistic and robust models of the oligopolistic interaction of electricity firms. This paper compares the two most popular models: Cournot and the Supply Function Equilibrium (SFE), and tests which model describes the observed market data best. Using identical demand and supply specifications, both models are calibrated to the German electricity market by varying the contract cover of firms. Our results show that each model explains an identical fraction of the observed price variation. We therefore suggest using Cournot models for short term analysis, as more market details, such as network constraints, can be accommodated. As the SFE model is less sensitive to the choice of the calibration parameters, it might be more appropriate for long term analysis, such as the study of a merger.supply function equilibrium;Cournot competition;electricity markets