Development of a variable water temperature control method for air source heat pump based on the supply-demand balance

•A control method for supply water temperature of air source heat pump is proposed.•This control method makes supply water temperature decrease by 3.7 °C.•Coefficient of performance of experimental unit increases by 22.88%.•A decrease of 26.16% in building heating energy consumption is achieved.•The percentage of PMV between −0.5 and +0.5 increases from 48.61% to 87.86%.