To address the conflict of peak-valley electricity price faced by electric-driven heat pump heating systems, this paper focuses on the impact of the dynamic changes in the heat pump’s coefficient of performance (COP) under variable operating conditions on the heating network energy storage strategy. Traditional energy storage strategies often focus on simple arbitrage through valley electricity price thermal storage, and neglect the significant decrease in COP caused by increased water supply temperature during thermal storage, which may lead to suboptimal strategies. This paper takes a large-scale 300 000 m2  sewage-source heat pump heating project in Qingdao as an example, establishes a dynamic simulation model considering the variable operating condition characteristics of the heat pump, and compares the conservative strategy of using only valley electricity price energy storage with the optimized strategy that additionally includes opportunistic flat electricity price energy storage. The results show that compared with the scheme using only valley electricity price energy storage (with a payback period of 1.75 years), the optimized strategy can shorten the project’s dynamic payback period to 1.37 years by more effectively avoiding peak electricity price periods. The research confirms that in energy storage scheduling, comprehensively considering the dynamic balance between electricity prices and the real-time COP of heat pumps, and opportunistically using flat electricity price periods for additional energy storage, are key to maximizing the overall economic benefits of the system. This study provides new perspectives and methods for the refined scheduling and economic evaluation of heat pump energy storage systems.