Supply function equilibrium models are used to study electricity market auctions with uncertain demand. We study the effects on the supply function equilibrium of a tax, levied by the system operator, on the observed surplus of producers. Such a tax provides an incentive for producers to alter their offers to avoid the tax. We consider these incentives under both strategic and price-taking assumptions. The model is extended to a setting in which producers are taxed on the benefits accruing to them from a transmission line expansion (a beneficiaries-pay transmission charge). In this setting, we show how this tax may lead to lower prices in equilibrium.

Competition between oligopolist electricity generators is inhibited by transmission constraints. I present a supply function equilibrium (SFE) model of an electricity market with a single lossless, but constrained, transmission line. The market admits equilibria in which generator withhold energy in order to induce congestion, which further increases their local market power. Under appropriate assumptions on cost and demand functions, I obtain a planar autonomous system of ordinary differential equations for the SFE. Computational methods are developed to solve the system while respecting monotonicity constraints on the supply functions. Using these methods I can calculate SFE in network markets that range from fully isolated to fully integrated. I also find network markets for which the SFE is not unique.

We construct a model of strategic behavior in sequential markets which exhibits a persistent forward price premium. On the spot market, producers wield market power while purchasers are price takers. Producers with forward commitments have less incentive to raise prices on the spot market. Purchasers are thus willing to pay a premium to producers for forward contracts.We argue that this type of forward premium is not susceptible to arbitrage by speculators on the forward market, since purchasers prefer forward contracts backed by producers.JEL: D43, G13, L12, L13, Q41

We construct a model of strategic behavior in sequential markets which exhibits a persistent forward price premium. On the spot market, producers wield market power while purchasers are price takers. Producers with forward commitments have less incentive to raise prices on the spot market. Purchasers are thus willing to pay a premium to producers for forward contracts. We argue that this type of forward premium is not susceptible to arbitrage by speculators on the forward market, since purchasers prefer forward contracts backed by producers.

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