High-temperature power-to-hydrogen based on solid oxide electrolysis cells (SOECs) is a promising energy storage technology. A large-capacity plant can be assembled from multiple SOEC modules by utilizing the inherent modularity and scalability of cell stacks. Despite the sufficient research on a single SOEC module, the intermodule coordination to optimize their performance as a group is rarely studied in the literature. Starting from common characteristics of SOEC, this paper proposes a management strategy based on the production-curve model of each module to exert the additional flexibility provided by a modular configuration. Specifically, the strategy optimizes the load allocation, including the switching arrangements among modules, while meeting the load commands and reserve requirements, as shown in Fig. 2. The optimization can be linearized into a mixed integer linear programming formulation for efficient problem solving. The strategy is proven effective in lowering operating costs in a numerical case. Moreover, the results suggest some valuable patterns, such as the shutdown preferences of less efficient and large-capacity modules and the equimarginal principle for running modules.