Most of today's consumed energy can be categorized as either electrical, chemical or thermal. Traditionally, the infrastructures for the supply with these energy forms have been engineered separately, often resulting in parallel but uncoordinated supply infrastructures. Various new technologies for conversion between these energy forms however start introducing a mutual dependence and an increasing substitution potential between these infrastructures, with combined cycle gas turbines playing a major role. To a certain extent, the mutual dependence also leads to redundancy effects and influences the reliability and availability of supply. This paper presents a model for analyzing and calculating expected reliability of supply and expected energy not supplied in such multi-carrier energy systems. The models can be used to identify the benefit and sensitivity of certain conversions as well as their limits in terms of reliability improvements. (C) 2008 Elsevier Ltd. All rights reserved.