In this presentation, I offer some reflections on a completed project on Institutional Rhythms that looked at the role that large and complex institutions – like hospitals – play in shaping patterns of demand for energy and travel. The NHS is the fifth largest employer in the world, it is the largest public sector contributor to climate change in Europe, and, through the delivery of its services, it is responsible for 26 million tonnes of carbon emissions each year. The project which is part of the DEMAND centre at Lancaster starts from the position that resources like energy, travel and goods that contribute to these total carbon emissions are consumed in the course of accomplishing everyday working practices. Drawing on examples and data collected from an ethnographic study of three large, acute NHS hospitals in the UK, I argue that everyday working arrangements, and hence patterns of total demand for energy and travel, depend on the socio-temporal organisation of hospital life. I describe how this analysis shows that notoriously difficult to shift peaks in energy demand, peak times for congestion and mobility, and resource intensive and problematic hospital timings (such as time of discharge and waiting times) are, in part, the products of fixed combinations and sequences of activities constituted by the rhythms of everyday life that exist both within and beyond the hospital. This research highlights new opportunities for unpicking, destabilising, and reconstituting the flexibility of such sequences and combinations of practices as a means of shaping demand for resources in large and complex institutions.In conclusion, I will reflect on some of the conceptual and empirical challenges I am currently grappling with in developing proposed future work on the fixity and flexibility of institutional rhythms and how such approaches might, in future, be adapted to examine other sites, for example, in considering demand for energy and travel in cities.