Achieving reductions in global anthropogenic emissions necessary to mitigate the worst effects of climate change will require significant reductions in energy demand. However, there are concerns that energy demand reductions involving lifestyle and behavioural changes might negatively impact peoples’ wellbeing. The work in this thesis studies the impacts of how people spend their time – commonly known as time-use – to try to understand whether this is the true, or whether energy demand could be reduced while improving wellbeing. Using the UK as a case study, this issue is examined by determining the energy use and wellbeing attributes of different activities and lifestyles, by modelling the impacts of shifts in time-use between activities, and by comparing the importance of three specific changes that might impact future energy use and wellbeing.

Firstly, based upon existing literature it is identified that there is a need to better understand the combined energy and wellbeing impacts of different activities and lifestyles. Combining UK time-use and energy consumption data, the energy intensity, enjoyment and sociability of time is studied. Comparing these metrics for different activities suggests that since the most enjoyable (and in some cases sociable) activities are generally the least energy-intensive, acceptable (or popular) lifestyle changes might exist that reduce national energy use and improve wellbeing. However, studying changes between 2000 and 2015 shows that while the population’s time became less energy-intensive, there was little change in average enjoyment and a reduction in sociability. Segmenting the population by age reveals that an ageing population could present a challenge since energy use broadly increases with age-group while social contact reduces. However, comparing occupations highlights opportunities for specific actions that could improve wellbeing and reduce energy use, while regional differences suggest that wellbeing might be improved without increasing energy use.

Having determined the energy intensity and wellbeing associated with different uses of time, the impacts of possible time-use changes are then studied. Acknowledging the difficulty in trying to predict how people might choose to re-allocate time in different situations, a sensitivity-based approach is used to study the impacts of a wide range of possible shifts in time between activities. The approach is then applied to explore the impacts of extreme lifestyle changes associated with COVID-19 lockdown measures in the UK and validated against real-world observations during the pandemic. While activity changes associated with lockdown measures reduce energy use, there are varying implications for peoples’ wellbeing, with the youngest appearing to be most negatively impacted but those able to work from home potentially benefiting. Although lockdown measures prevented some of the most enjoyable and sociable activities from happening, alternative activity changes could be supported in future that reduce energy use while improving wellbeing.

Finally, time is used as a basis to compare the importance of different types of changes and help to prioritise actions. This is demonstrated by studying the combined impacts of three example changes – greater home working, changes in commuting transport modes and car intensity – on office workers’ energy use and wellbeing. The results show that working from home could have a greater impact upon office workers’ average energy use and enjoyment than changes to commuting modes, but that the social contact provided by the office could be difficult to replace. The study also demonstrates different ways that energy savings might be achieved through home working, shifts in commuting modes and changes to vehicle intensity. This approach could be used more widely to compare a broader range of changes, understand their interactions and different ways to achieve outcomes, and help to identify those changes that are most important to reduce energy use and improve wellbeing.

The work presented in this thesis shows that time-use can be used as a basis to examine energy demand and wellbeing together. Using time-use to link these issues enables trade-offs or co-benefits due to different uses of time to be determined and allows rebound effects to be considered. The results suggest that reducing energy use can be achieved at the same time as improving wellbeing. The hope is that the approaches and findings presented in this thesis can provide a basis for wider discussion and a platform for future work to support climate change mitigation strategies that are positive for both the environment and society.