Designing regulatory contracts for the operators of power transmission netw
orks has become a critical policy issue in the United States. In this paper
, a regulatory contract is proposed that induces network operators to optim
ally expand the grid, which is crucial for the emergence of efficient whole
sale power markets, while also satisfying the other traditional regulatory
objectives. The proposed mechanism is readily implementable, since it build
s on a contract currently in place in England and Wales.