Warming up incoming fresh air can account for half the space heating demand of a well insulated residential building. Variable air supply (e.g. by demand control) and energy recovery with an air-to-air heat exchanger reduce that demand. However in real-world settings, expected cost and environmental impact savings may not arise, leading to a so-called performance gap. This long-term study followed the building occupancy and electricity consumption of a modern family home in central Sweden, heated using a ground-source heat pump. Over three winters, three mechanical ventilation systems were trialled. Two had heat recovery – flat-plate or rotating wheel – while one was an exhaust system equipped with sensors for demand control of individual rooms. Variable airflow by simple schedule was also evaluated. In consistently subzero temperature conditions, the rotating wheel offered energy savings of at least 11 % compared to the flat-plate device. There was however no evidence (within a warmer temperature range) of a clear difference in heat demand between the exhaust system trials and those with heat recovery. The timing of electrical demand periods suggested that this apparent heat recovery performance gap related to temperature regulation and frost protection within the air handling units. In this real-world setting, with a ground-source heat pump providing baseload warmth, heat recovery ventilation provided limited electrical energy savings, and appeared to align the timing of power demand peaks more closely with falling outdoor air temperature.