Abstract Fuel poverty is perhaps the strongest adverse social impact resulting from the inefficient consumption of energy in the domestic sector. Despite considerable research examining the plight of those affected, there has been very little empirical work examining the relationship between fuel poverty and thermal comfort and the extent of indoor cold strain resulting from inadequately heated housing. Furthermore, the effects of fuel poverty on household occupancy have not been addressed formerly. This paper employs a new national household survey of Ireland—a country with a level of fuel poverty similar to Britain—to examine these key issues. Both self-reported and objective measures of thermal comfort are utilised, and the study pays particular attention to the age profile of those affected by thermal discomfort. The results show, inter alia, that two-thirds of fuel-poor householders demonstrate cold strain, and over half of elderly households endure inadequate ambient household temperatures during winter.