The state-of-the-art query techniques in power grid monitoring systems focus on querying history data,which typically introduces an unwanted lag when the systems try to discover emergency situations.The monitoring data of large-scale smart grids are massive,dynamic and highly dimensional,so global query,the method widely adopted in continuous queries in Wireless Sensor Networks (WSN),is rendered not suitable for its high energy consumption.The situation is even worse with increasing application complexity.We propose an energy-efficient query technique for large-scale smart grids based on variable regions.This method can query an arbitrary region based on variable physical windows,and optimizes data retrieve paths by a key nodes selection strategy.According to the characteristics of sensing data,we introduce an efficient filter into the each query subtree to keep non-skyline data from being retrieved.Experimental results show that our method can efficiently ret the overview situation of any query region.Compared to TAG and ESA,the average query efficiency of our approach is improved by 79％ and 46％,respectively;the total energy consumption of regional query is decreased by 82％ and 50％,respectively.