As the world is transitioning from conventional to renewable energy sources, governments and energy utilities face the challenge to match the supply profile of these intermittent sources to the energy demand. Energy storage is being considered as one of the potential solutions to cope with the variability of renewables. Belgium is not only challenged by the transition to renewable energy but must also deal with the total nuclear power phase-out by 2025. The country significantly depends on the seven nuclear power plants since they account for more than half of the national electricity production (depending on the availability of the reactors). The Belgian TSO Elia has investigated the urgency of adequacy and flexible electricity sources and proposed a Capacity Remuneration Mechanism (CRM), which should encourage investments in generation capacity to maintain the security of supply in Belgium. All awarded capacity providers of the competitive auction receive financial compensation for the availability of their generation capacity in the Belgian energy market. Eneco is one of the largest utility companies in the Belgian electricity market for consumers and considers participating in the Belgian capacity auction with EES capacity. The competitiveness of EES is assessed based on the constructed competitiveness evaluation model. The model considers the long-term capacity remuneration, possible costs related to the capacity market, storage costs, and revenue derived in the electricity market. A capacity provider is considered as competitive if the expected costs are smaller than the expected revenue from being in the capacity market. The net present value (NPV) approach is chosen to investigate the economic competitiveness of EES. The storage costs, intraday market income, payback obligation, and FCR income are modelled for the photo years 2020, 2025 and 2030. The Battery Energy Storage System (BESS) will be deployed in the Frequency Containment Reserve (FCR) market and intraday market because of the largest revenue potential. The expected intraday market income is assessed by the software tool Linny-R which applies the optimization technique linear programming based on the rolling horizon approach. BESS operating only in the intraday market is not expected to be competitive because of the relatively high required capacity remuneration above € 100/kW/year. Auction clearing prices in other European CRMs are below € 50/kW/year. BES does not need capacity remuneration from 2025 onwards with today’s average FCR price. However, it is not very likely that the FCR price stays the same in the future. More realistic is 35% capacity price reduction from the average FCR price scenario of € 79.000/MW/year to the minimum FCR price scenario of € 51.000 /MW/year. BES might be competitive in this scenario with a relatively high de-rating factor and no payback obligation of the CRM. In the halved today’s average FCR price scenario, BES will not be competitive in 2025 given the relatively high required capacity remuneration of minimum capacity remuneration of at least € 69/kW/year. The results of this research are not convincing to regard BES as a competitive technology in the upcoming Belgium capacity market. Revenue stacking by combining the FCR and intraday market income would increase the competitiveness of BES and is necessary. Further research should focus on deployment strategies of BESS in different markets and FCR price developments.