The paper presents an analysis of the effects of irreversibility on the performance of a reverse Joule-Brayton cycle heat pump for domestic heating applications. Both the simple and recuperated (regenerative) cycle are considered at a variety of operating conditions corresponding to traditional (radiator) heating systems and low-temperature underfloor heating. For conditions representative of typical central heating in the UK, the simple cycle has a low work ratio and so very high compression and expansion efficiencies and low pressure losses are required to obtain a worthwhile COP. An approximate analysis suggests that these low loss levels would not necessarily be impossible to achieve, but further investigation is required, particularly regarding irreversible heat transfer to and from cylinder walls. In principle. recuperation improves the cycle work ratio, thereby making it less susceptible to losses, but in practice this advantage is compromised when realistic values of recuperator effectiveness are considered. (C) 2009 Elsevier Ltd. All rights reserved.