The electric industry has been experiencing an exponential growth of battery energy storage deployments; however, there is industry wide inconsistency with determining appropriate values for operations and maintenance (O&M) planning. This study builds from previous research that developed an excel-based tool with a bottom-up method of estimating O&M costs for battery energy storage systems. The overall objective for this study and continued tool development is to provide planners with a clear and concise understanding of O&M costs and the ability to evaluate the impact O&M strategies and project attributes have on costs over an asset’s life. Key updates for this year’s study include updating cost forecasts and taking a deeper look at degradation modeling its impact on augmentation and replacement costs.