An exergoeconomic assessment using exergy-cost-energy-mass (EXCEM) analysis is reported of a copper-chlorine (Cu-Cl) thermochemical water splitting cycle for hydrogen production. The quantitative relation is identified between capital costs and thermodynamic losses for devices in the cycle. A correlation detected in previous assessments, suggesting that devices in energy systems are configured so as to achieve an overall optimal design by appropriately balancing thermodynamic (exergy-based) and economic characteristics of the overall system and its components, is observed to apply for the Cu-Cl cycle. Exergetic cost allocations and various exergoeconomic performance parameters are determined for the overall cycle and its components. The results are expected to assist ongoing efforts to increase the economic viability and to reduce product costs of potential commercial versions of this process. The impacts of these results are anticipated to be significant since thermochemical water splitting with a copper-chlorine cycle is a promising process that could be linked with nuclear reactors to produce hydrogen with no greenhouse gases emissions, and thereby help mitigate numerous energy and environment concerns. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.