Correspond with population growth, Indonesia's energy consumption has been increasing for the past decade. In the last few years, the demand for energy increases by 7.1% every year. The highest energy consumption for a building is in the cooling sector. Much research has been conducted to increase the performance of cooling equipment to reduce their energy consumption. Past research found that hydrocarbon (R290), a natural refrigerant, has higher performance than the most commonly used refrigerant in Indonesia. Furthermore, the hydrocarbon is environmentally friendly, unlike HCFC and HCF. This research is designed to analyze the effects of sub-cooler on the performance of R290 chiller used in an auditorium air conditioning system, and the results show that there is an increase on COP by 6.9% when using sub-cooler on medium part cooling load operation.