Bi-Lo Supermarket in this study is located in sub-tropical coastal area in Queensland, Australia. The main objective of air conditioning in any building or supermarket is to provide comfort to the occupants and patrons of the conditioned space, an objective the air conditioning system at Bi-Lo is struggling to achieve. The objectives of this case study are to identify the factors contributing to poor performance of air conditioning system at Bi-Lo and how to improve the economic life, air distribution throughout the store and system efficiency. Energy audit and performance calculation of the existing systems is performed. This study found that the premature aging of the system and consequent loss in economic life and poor performance are due to a combination of the coastal climate and poor maintenance of the system. Another contributing factor in the systems poor performance was due to uneven distribution of the conditioned air within the store. The cooling load required for the store is calculated using CAMEL, a heat load calculation program developed by Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH)), based on the local climatic data, Dailey people flow to store, building survey data, properties of building materials, etc. This study discussed and recommended that the appropriate performance and improved economic life of the Bi-Lo air conditioning system can be achieved through correct selection of air conditioning units (based on new coolingload calculation), duct redesign and applying correct installation techniques and maintenance of the system.