Property Assessed Clean Energy (PACE) finance is a new and growing municipal approach to support energy efficiency and renewable energy upgrades in commercial buildings in the United States. As of February 2013, there were 16 commercial PACE programs accepting applications to finance building efficiency projects. Most of these have been active for less than a year, and some are just now working on their first projects. As this new market develops, early-stage PACE programs have taken different approaches to program design and administration. Lessons learned from their experiences may well shape the overall success of PACE in the years to come.