A Capacity Market that Makes Sense

Peter Cramton and Steven Stoft , The Electricity Journal 18(7) , 43-54 , September 2005.

We argue that a capacity market is needed in most restructured electricity markets, and present a design that avoids problems found in the early capacity markets. The proposed market only rewards capacity that contributes to reliability as demonstrated by its performance during hours in which there is a shortage of operating reserves. The capacity price responds to market conditions, increasing when and where capacity is scarce and decreasing to zero when and where it is sufficiently plentiful. Market power in the capacity market is addressed by basing the capacity price on actual capacity, rather than bid capacity, so generators cannot increase the capacity price by withholding supply. Actual peak energy rents (the short-run energy and reserve profits of a benchmark peaking unit) are subtracted from the capacity price. This allows the capacity market to more accurately control short-run profits and suppresses market power in the energy market. This design both avoids and hedges energy market risk, and by suppressing market power avoids regulatory risk. Risk reduction saves consumers money as do the performance and investment incentives inherent in the pay-for-performance mechanism.

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