Energy storage will be necessary for a future power system with high penetration of renewable sources, mainly, wind and solar, to ensure the stability of the grid. In this context, power-to-chemicals is a promising concept for a medium/long-term storage horizon and a wide range of capacities. Within this alternative, ammonia rises as one of the fuels with the highest potential in a scenario targeting decarbonization. The first step is the production of ammonia using renewable energy sources, followed by its transformation into energy. This second area requires a deeper analysis at process scale in order to introduce this technology into the future power system. In this work, an assessment of an ammonia-based power plant is presented, focusing on the thermo-chemical route. A combined cycle is evaluated, considering different gas clean-up technologies to recover valuable components and comply with environmental restrictions. As a result, the total efficiency of the power facility reaches about 40%, limited by the maximum temperature allowed in the gas turbine. The influence of the price of ammonia is also evaluated due to the paramount importance of this parameter. The production cost ranges from 0.2 to 0.6€/kWh, with the lowest level corresponding to a scenario in which there is a significant reduction in the cost of renewable power generation and electrolysis technology. Therefore, the feasibility of the use of ammonia as an energy storage alternative is demonstrated, providing a powerful platform for the implementation of a power grid with high penetration of fluctuating sources.