Abstract A method for formulating and solving a decentralized unit commitment problem is presented in this work. The method, which extends the alternating direction method of multipliers (ADMM), is presented along with several heuristics and refinements to mitigate oscillations and traps in local optimality that result from the nonconvexity of unit commitment. We present and discuss the promising results from testing the method on large-scale systems of more than 3000 buses. The scalability observed so far suggests that this method is a practical option for use with large systems and may provide a significant benefit for computational speed.