• Time-use data can reveal connections between energy demand and wellbeing.
• Analysis of time-use could stimulate differentially-targeted policy interventions.
• Lockdown reduced energy demand but was difficult for students and sole occupants.
• Policies to support home working could reduce energy use and improve wellbeing.
• Work sociability could be replaced with local leisure and libraries as workspaces.
Mitigating climate change will require significant reductions in energy demand, such as through lifestyle changes to emphasise lower-energy activities. The COVID-19 lockdowns demonstrated that reducing energy use is possible, but with substantial and unequal impacts on wellbeing and the risk of unintended increases in energy use elsewhere. To show which lifestyle changes could reduce energy use and improve wellbeing, we model how shifts in time spent on different activities impact energy use, enjoyment and sociability for seven social groups. We validate our model using data from the UK COVID-19 lockdown and demonstrate that lockdown measures did reduce energy use, with some benefits to those employed, but with negative consequences for the wellbeing of younger people and those living alone. By testing the effect of individuals’ choice of rebound activity, we highlight cases where policies aiming to reduce energy-intensive activities could backfire by increasing overall energy use or reducing wellbeing. While greater home working and less travel could reduce energy use, our results point to the need for new forms of social interaction to replace the workplace, and the importance of local sport and leisure facilities to enable more time for low-energy, enjoyable and sociable activities that improve wellbeing.