Purpose: The Green remodeling Project for public buildings aims to improve the energy efficiency of older buildings and reduce greenhouse gas emissions, with the primary goal of extending these efforts to private buildings. However, the green remodeling projects apply uniform energy technology elements without considering the usage and energy consumption behavior of the target buildings, making it difficult to implement suitable energy technologies for each building. Additionally, there is a difference between the estimated construction cost and the actual construction cost for green remodeling by estimating the construction cost using the same energy technology standard unit cost. Furthermore, the subjective opinions of various green remodeling business operators select energy technology products that only meet the support conditions, not the requirements of a specific building, which can result in high costs compared to energy savings. In this study, a cost-benefit optimization process for green remodeling of public buildings was proposed, energy savings were analyzed through an M&V (Measurement & Verification) simulation model. Method: We investigated the problems of the process in public building green remodeling projects and proposed a cost-benefit optimization process that can optimize construction costs compared to energy savings based on the problems. In addition, we performed M&V with actual energy usage using a dynamic simulation tool (DesignBuilder) and analyzed energy savings through simulation models of various energy performance levels. Result: The energy saving for the improvement model was confirmed to be at least 5% and at most 53% according to the defined technical elements and levels.