As renewable energy production becomes more prevalent, the challenge of producing renewable dispatchable fuel for the transportation sector remains unresolved. One promising approach is to produce hydrogen from solar energy with a two step thermochemical cycle which utilizes an oxygen storage material (OSM) to split water through two reversible reactions. Due to the strong coupling between reactor design, operational parameters, and OSM properties, the direct comparison of two OSMs is not straightforward. In order to guide the designs of OSMs for two-step thermochemical hydrogen production, a methodology is developed to model the max performance possible for a two-step thermochemical cycle. The novel contribution of this model considers the strong coupling between reactor operation, OSM properties, and reactor performance. Next, a method for screening and evaluating new OSMs which utilizes thermogravimetric analysis (TGA) is proposed. With this data, the modeling method previously developed is applied to determine maximum reactor efficiency possible with new materials. This allows many materials to be evaluated quickly, and facilitates further characterization new OSMs. Additionally, by comparing the predicted maximum efficiency of a new material with the efficiency of current ones, this method facilitates the comparison of two different OSMs on equal footing.