Abstract The performance evaluation for a residential window air conditioning system with micro-channel condensers has been performed. First, a series of wind-tunnel calorimeter tests are conducted for two different prototype micro-channel heat exchangers. The measured heat transfer and pressure drop characteristics for the heat exchangers are then compared to four conventional finned round tube designs, which were obtained using a validated simulation model for identical air and refrigerant inlet conditions. Finally, two prototype micro-channel condensers are installed in the system and system performance tests are conducted. System characteristics such as capacity, energy efficiency ratio, and suction and discharge pressures and temperatures are presented, compared to those for the conventional system. Refrigerant charge amount for a window air conditioner with a micro-channel condenser is decreased by 35%, and the condenser core volume and weight can be reduced by 55% and 35%, respectively, compared to the conventional baseline system.