This paper investigates and compares the energy saving potential of air-cooled vapor compression air conditioning systems by using liquid pressure amplification (LPA), evaporative-cooled condenser (ECC) and combined LPA and ECC strategies. The applicability, limitation and energy performance of these strategies are discussed. For the purpose of this study, an existing direct expansion rooftop package of a commercial building is used for experimentation and data collection. The system under investigation is extensively equipped with a number of instrumentation devices for data logging. Theoretical-empirical mathematical models for system components were developed first, while a numerical algorithm together with monitored data and a mathematical model implemented on a transient system simulation tool is used to predict the performance of each strategy under transient loads. The integrated simulation tool was validated by comparing predicted and measured power consumption of the rooftop package. Comparing between LPA and ECC methods shows that for the ambient temperatures less than 27 degrees C the LPA is more effective method while for ambient temperature greater than 27 degrees C the ECC system is more efficient. our results also demonstrate average energy savings of 25.3%, 18.3% and 44.2%, respectively for LPA, ECC and combined LPA and ECC methods. (C) 2014 Elsevier B.V. All rights reserved.