The primary aim of this study was to analyse the significance of household temperature in determining the amount of potential energy savings taken back in the form of an increase in the comfort temperature following energy efficiency improvements. If the dual goals of energy conservation and affordable warmth for low-income households are to be attained, the nature of takeback must be more thoroughly understood so that the full benefit of energy efficiency measures can be assessed along with the carbon/energy savings. However, very little analysis has been carried out to quantify the benefit taken as warmth. This research examines the results of a number of monitored energy efficiency projects undertaken in Britain over the past 20 years to try to determine the most important influences on temperature takeback. The main findings are: the internal temperature is the main determinant on the amount of benefit from energy efficiency measures that will be taken as an increase in comfort rather than as an energy saving; at 16.5 degrees C, the current average temperature of housing in Great Britain, about 30% of the benefit of an energy efficiency improvement would be taken as a temperature increase and the rest as an energy saving; at temperatures as low as 14 degrees C - still frequently found in low-income households - only half of the energy saving will be achieved and the remainder would be taken as a temperature increase; 20 degrees C is the most likely whole house comfort temperature in an energy efficient house and it is only in these circumstances that further improvements will achieve the full energy saving; there has been a narrowing of the gap in average indoor winter temperatures of the different tenure types and tenure alone is no longer a definitive indicator of household temperature; living room temperature is not a good indicator in the UK of whole house average temperature, as a warm living room may be found in an otherwise cold house, particularly in low-income households without central heating; as there is now little difference between the average temperatures of local authority and owner occupied households, there should be little difference in the overall degree of takeback between these two tenures; energy efficiency measures which increase radiant temperature, such as double glazing, enable the occupants to be comfortable at a lower air temperature and thus reduce the degree of takeback by up to 20%; there is a lack of suitably monitored and analysed projects to enable a rigorous assessment of takeback, particularly for higher income households; the present low levels of warmth and slow rate of improvement in average temperatures will mean that investment in the energy efficiency of the UK housing stock will fail to achieve the predicted energy savings for at least another 15 years.