Physics-informed capacity sizing of whole-house air conditioners integrating building thermal performance and dynamic operating behavior

Air-source heat pumps (ASHPs) have been widely adopted in residential buildings for heating and cooling because of their high efficiency and environmental benefits. However, selecting appropriate equipment capacity remains a key challenge in design. Traditional area-based capacity sizing methods and maximum-load-based sizing methods both have inherent limitations, as actual thermal loads vary significantly depending on the building’s insulation performance. Moreover, the recent increase in extreme heat days caused by global warming has substantially intensified cooling demand, further highlighting the need for a more rational capacity sizing approach. To address this issue, this study proposes an integrated simulation-based sizing method applicable at the early design stage, which combines building thermal performance with ASHP operational characteristics for capacity determination. Using only manufacturer-provided performance data, the method can accurately estimate system efficiency, electricity consumption, maximum heating and cooling capacities, and defrost duration under arbitrary operating conditions. Case studies with different insulation levels and system sizes demonstrate the effectiveness and practical applicability of the proposed method for optimizing ASHP capacity selection. • Coupled building-HP simulation evaluates efficiency under arbitrary conditions. • Quantified climate and load impacts on max capacity and defrosting cycles. • Compares deficiency duration, defrost time, and electricity consumption. • Facilitates optimal capacity sizing for both comfort and economic benefits.