Commercial Building Retro-commissioning activity has increased in recent years. Retro-commissioning is a process of identifying and implementing systems improvements in existing buildings, with an emphasis on using low cost operational and maintenance tune-ups and diagnostic testing instead of capital intensive retrofits. LBNL recently conducted a study of 8 participants in the Sacramento Municipal Utility District Retro-commissioning program. The study evaluated the persistence of energy savings and measure implementation, in an effort to identify and understand factors that can improve the longevity of retro-commissioning benefits. Results showed a 59% implementation rate of recommended measures. Some other findings were:Approximately 65% of the peak retro-commissioning savings persisted beyond four yearsAll the sites said that retro-commissioning is beneficial to their operationsA majority of the measure implementation costs were absorbed into regular operation and maintenance budgetsThe most frequently reported down side was the large time demands on the building engineering staff. However, all respondents thought it was worth the price.Training was the most cited non-energy benefit of retro-commissioning.