Should Merchant Transmission Investment be Subject to a Must-offer Provision?

Merchant electricity transmission investment is a practically relevant example of an unregulated investment with monopoly properties. However, while leaving the investment decision to the market, the regulator may decide to prohibit capacity withholding with a must-offer provision. This paper examines the welfare effects of a must-offer provision prior to the capacity choice, given three reasons for capacity withholding: uncertainty, demand growth and pre-emptive investment. A must-offer provision will decrease welfare in the first two cases, and can enhance welfare only in the last case. In the presence of importer market power, a regulatory test might be needed.