Toward Efficient Resource Adequacy: The Role of Shared Reserves in China’s Power Grid

China's pursuit of carbon neutrality will entail a transformation of its power generation portfolio through extensive investment in renewable energy, underscoring the need for expanding planning and operating reserves to maintain power system reliability. However, efficient reserve management is critical, amid evolving electricity market reforms, to avoiding overcapacity. Here, we quantitatively assess spatiotemporal coordination strategies through regional reserve sharing within China's interconnected power grids. Our results demonstrate that high coordination strategies reduce the planning installed capacity by up to 9.2 % in Southern China grid region in 2035 and lower capital expenditures by 3–4 % (equivalent to USD $243.0–258.4 billion in present value) over a 30-year horizon compared to the low coordinated case. Additionally, sharing operating reserves within the East China grid region reduces reserve capacity procurement by 16 % in 2035 and cuts annual reserve market costs by 5–8 % (about $5.8–8.3 billion) compared to the unshared case. These findings suggest that regional coordination can enhance economic efficiency, representing an under- utilized lever to facilitate power system decarbonization.