Transition to Centralized Unit Commitment An Econometric Analysis of Colombia's Experience

This paper attempts to shed light on the relative merits of centralized electricity markets with multipart bids and dispatch using an MIP-based unit commitment optimization approach vs. self-committed markets with linear energy supply curves. We conduct an empirical study of data from the Colombian market, which in 2009 transitioned from a self-commitment paradigm to a centralized unit commitment approach where generators offer a linear supply function for energy along with start-up costs while the commitment and dispatch are determined by the system operator using MIP-based optimization. The results indicate that the transition to centralized dispatch has resulted in productive efficiency gains through a decrease in production costs. However, these gains have not translated into wholesale price decreases; in fact, wholesale prices increased after the change in the dispatch approach. These results suggest that productive efficiency gains have been captured by suppliers through the exercise of market power.