Retro-commissioning is a process to improve the efficiency of an existing facility’s operating equipment and systems.  It can often resolve problems that occurred during design or construction, or address problems that have developed throughout the facility’s life as equipment has aged, or as electricity usage, or production, has changed.  A retro-commissioning assessment in California with Onsite involves a systemic evaluation of opportunities to improve energy-using systems.  Many of the  operations’ maintenance and control improvements cost little or nothing to implement, yet some can have big effects.  In today’s complex facilities, systems are highly interactive, with sophisticated controls that can create a trickle-down effect on building plant operations – small problems have big effects on performance.  All facilities can experience performance degradation over time and need retro-commissioning for complete energy efficiency.