EYP developed a phased central chilled water plant that would ultimately serve a total of 10 buildings comprising of 500,000 SF. The first phase of construction consisted of two 600 Ton chillers, one high efficient centrifugal chiller and one gas-engine driven chiller. The high-efficient electric chiller was equipped with a variable speed drive to improve compressor efficiency. The gas-engine chiller is twice as efficient as a gas absorption chiller and was equipped with heat recovery that recovers heat from the engine to generate summer hot water reheat requirements. This prevents Swarthmore from running its large central high-pressure steam boiler plant inefficiently to satisfy the small summer hot water demand.