This article details comprehensive energy and exergy analyses of the sulfuric acid decomposition process of the sulfur-iodine (SI) thermochemical cycle for hydrogen production. Energy and exergy efficiencies of the proposed process were evaluated over a variety of reaction temperatures and pressures. At an atmospheric temperature of 25 degrees C, the calculated values of exergy destruction of the H2SO4 decomposer ranged between 157 kJ/mol and 360 kJ/mol over reaction temperatures of 800-1000 degrees C and pressures between 1 and 50 atm. It was shown that the exergy efficiency of the H2SO4 decomposer improved with an increase in reaction temperature, while reaction pressure had a negative effect on exergy efficiency. Crown Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.