The study investigated the effect of the improved partial load COP of adsorption chillers on the cogeneration system in an office building. The partial load COP of the adsorption chiller was maximized by optimizing the cycle time. The COP of the adsorption chiller was increased with smaller partial load ratios by the extended cycle time. The performance of the cogeneration system with an adsorption chiller was analyzed by simulation, and the energy saving ratio of the system was presented. The energy saving ratio was compared with that by the cogeneration system with an absorption chiller. The results showed that the adsorption chiller was advantageous given that the adsorption chiller had the same rated COP value as the absorption chiller.