As energy storage becomes increasingly important for renewable energy integration and grid stability, battery performance and efficiency are receiving greater attention. Redox flow batteries are gaining interest for stationary energy storage because of their flexible capacity, scalable design, and potential for long operating life. However, understanding redox flow battery efficiency is essential when evaluating their technical performance and economic viability. Energy losses during charging, discharging, and system operation can influence electricity costs, operating expenses, and overall project returns. This article explores how redox flow battery efficiency is measured, the factors that influence performance, the relationship between efficiency and cost, and practical ways to improve energy storage system operation.