Understanding demand flexibility in the residential sector depends on understanding the causal link between household occupants' activities and resulting electricity demand. Self-reported electricity use via time-use diaries is often used as a direct descriptor of occupants' activities and has been integrated into residential electricity demand simulation models. Conversely, smart meter electricity demand data is increasingly used to infer occupants' activities. Underlying both these approaches are a number of unverified assumptions about people's perceptions of their energy use, the accuracy with which they report these activities and the physical operation of electrical devices. This paper carries out a comparison between self-reported energy-related activities and monitored electricity demand in 15 households over a week-long time period, with focus on electric hot water cylinders and heat pumps as appliances with large potential for demand flexibility. This comparison quantifies the extent to which self-reported activity is a predictor of electricity demand and conversely, whether electricity demand can accurately identify occupant activity. Results show that, although there is significant variation across households, self-reported activity tends to be a reasonably good predictor of electricity demand. However, due to the intervention of thermostat-controlled devices, electricity demand is not a good indicator of occupant activity. (C) 2018 Elsevier B.V. All rights reserved.