Vertical separation of transmission control and market efficiency in the wholesale electricity market

This study examines how vertical separation of transmission control affects the wholesale market efficiency in the electric power industry. We analyze a unique regional electricity wholesale market in the U.S. where initially restructuring only occurred in the transmission sector. Following a commonly-used best dispatch model (Wolfram, 1999; Borenstein et al., 2002), we simulate competitive benchmark prices and compare with the best estimates available for actual prices to measure price-cost markups of the wholesale market. Empirical results demonstrate that the vertical separation of transmission control led to a significant increase in market markups in peak-load hours, documenting evidence of enhanced market power. Although we also find a reduction in the price-cost margin in low-demand hours, we reserve caution for this finding.