A novel method is proposed to analyze the reasonable utilization rate of renewable energy considering the cost of adjustable resources in provincial area. The formula for calculating the utilization rate of renewable energy in provincial region is quantitatively given by combining the power supply load of the power system in the target region and the operating constraints of non-hydro conventional units. And then the analytical expression for the utilization rate of renewable energy based on the cost of consumption is proposed by combining with the provincial power supply–demand balance model that takes into account the output of renewable energy. The results of one case study show that the renewable energy utilization rate gradually increases with the growth of flexibility resources, but the effect of renewable energy consumption per unit of new flexibility resources gradually decreases, and the reasonable renewable energy utilization rate in the analyzed area in some year is 0.9886.