The aim of this study is to better understand the external and internal drivers that affect residential air-conditioning (A/C) use decisions and occupant comfort. Field observations were carried out using instrumental measurements and smartphone questionnaires, recording householder's A/C usage patterns, indoor/outdoor climatic factors, perception of thermal comfort and adaptive behaviours. Throughout the 2-year monitoring period, a total of 4,867 A/C use events and 2,105 online comfort questionnaires were collected from 42 homes in Australia. The householders' neutral temperature was estimated to be 2 degrees lower than that predicted by the ASHRAE 55's adaptive model. Despite the lower-than-expected neutrality, comfort zone widths for 80% acceptability were found to be 9K in residential settings, which is 2K wider than that expected by the adaptive model. Our findings indicated that people in their homes are more adaptive to, and tolerant of significantly wider temperature variations than expected (in particular cooler temperature conditions). Based on the analysis of the results, an adaptive model that can be used for the assessment of residential thermal comfort is proposed in this paper. This study also revealed the householders' thermal adaptation behaviours as a function of temperature variations, which can be utilised in building energy modelling softwares.