Normal ventilation without heat recovery in an air conditioned room would cause additional energy consumption. This study proposes a novel window mini heat-pump air exchanger (WMHPAE) unit which requires low power to operate. During its operation, the small-scale heat pump can cool the fresh hot outside air in the evaporator before sucking it into the room and cool the condenser by the indoor exhausted cold air in summer, which would achieve the ventilation as well as helping to increase COP of the micro-compressor heat pump. The prototype was built and tested under laboratory conditions with different parameter controls including power consumption, axial fan speed and temperature differences between indoor and outdoor. The results show that WMHPAE units could provide fresh air exchange with low energy consumption. The unit could also be retrofitted in residential buildings to contribute to better facades as it enjoys compact size to fit the widow frame. However, further real-life investigation and improvement are still needed for the WMHPAE unit.