Energy storage systems are crucial in dealing with challenges from the high-level penetration of renewable energy, which has inherently intermittent characteristics. For this reason, various incentive schemes improving the economic profitability of energy storage systems are underway in many countries with an aim to expand the participation rate. The electricity charge discount program, which was introduced in 2015 in Korea, is one of the policies meant to support the economic feasibility of demand-side energy storage systems. This paper quantitatively evaluated the impact of the electricity charge discount program on the economic feasibility of behind-the-meter energy storage systems. In this work, we first summarized how electricity customers can benefit from behind-the-meter energy storage systems. In addition, we represented details of the structure that make up the electricity charge discount program, i.e., how the electricity charge is discounted through the discount scheme. An optimization problem that establishes a charge and discharge schedule of an energy storage system to minimize each consumer’s electricity expenditure was defined and formulated as well. The case study results indicated that the electricity charge discount program has improved the profitability of behind-the-meter energy storage systems, and this improved profitability led to investment in behind-the-meter energy storage systems in Korea. As a result of the electricity charge discount program, Korea’s domestic demand side energy storage system market size, which was only 27 billion dollars in 2015 in Korea, has grown to 825 billion dollars in 2018.

As part of efforts to cope with climate change, countries around the world have decided to supply photovoltaic (PV) power. However, since the integration of PV affects the reliability and stability of a power system, increasing the penetration of PV generation requires better system flexibility. For this reason, many countries have recently established policies to disseminate energy storage systems (ESS). In this paper, we aim to evaluate the effectiveness of policies regarding ESS as a way to increase PV integration. We analyzed whether the policies were effective in spreading ESS to eventually increase PV integration. To do this, we first described the Korean government’s policy of establishing a profit structure for ESS through the Renewable Energy Certificate (REC) market and analyzed its effects on economic feasibility. We also analyzed how much the investment in ESS for PV integration has risen and assessed the contribution of spreading ESS to disseminate PV power. We found that ESS for the integration of PV have grown to a 41.0% share of Korea’s ESS market in kW, and 32.8% in kWh, while expanding the PV market by 13.7%.

Multi-region integrated multi-energy system (MES) combines electricity, heat, and hydrogen networks to improve energy efficiency and reduce carbon emissions. Planning such interregional systems remains difficult because of nonlinear energy interactions, spatial–temporal coupling, and various regulatory constraints. This paper reviews optimization-based planning methods for multi-region MES and explains how recent studies manage system coordination, uncertainty, and trade-offs among energy carriers. The reviewed literature was selected from major databases—Scopus, Web of Science, and IEEE Xplore—to reflect the development of optimization approaches such as mixed-integer programming (MILP/MINLP), metaheuristic algorithms, model predictive control, and data-driven frameworks. The literature spans from 2009 to 2025, capturing both early foundational studies and the most recent advances in optimization-based MES planning. The analysis summarizes the main progress, technical limitations, and remaining challenges related to policy integration, investment interaction, and regional coordination. The paper concludes that future research should establish scalable optimization methods that link technical design, economic performance, and policy goals in integrated energy planning.