Vertical Economies and the Costs of Separating Electricity Supply--A Review of Theoretical and Empirical Literature

Motivated by the European movement towards a separation of electricity networks from the competitive functions generation and supply this paper reviews theoretical and empirical literature on vertical synergies in electricity supply. In the analysis a clear distinction is made between four different unbundling options leading to different forms and magnitudes of synergy losses. Apart from coordination economies a main source of scope economies seems to result from a market risk effect if generation and retail are separated. Accordingly, the European policy of network unbundling (either transmission or distribution) results in synergy losses between 2 and 8 percent due to coordination losses, while an unbundling option that includes a separation between retail and generation, as observed in some U.S. states, may lead to a permanent cost increase of 20 percent or more due to a significant risk increase.