What can we say about the longer-term impacts of a living lab experiment to save energy at home?

There is a wide evidence base on various interventions to change energy behaviours in households, but limited evidence on their long-term effects. It is argued that interventions in individual behaviours are subject to attrition over time following the withdrawal of the intervention. Evaluation of these arguments is difficult since the conditions and composition of households change over time, making it hard to isolate the effects of a behavioural intervention several years later. Social practice theory argues for interventions that do not target individual attitudes or behaviours but focus instead on household practices (such as laundering and heating homes), and the underlying notions of cleanliness and comfort that are the causes of energy use in households. In contrast to behaviours, practices are also seen as socially shared, bundled with other practices, and embedded in social structures and processes. Practices are durable entities that persist over time; true practice change would hence entail durable intervention impacts. Our paper qualitatively investigates the long-term effects (2018–2023) of a practice-based living lab intervention that aimed to influence laundry and heating practices in Finnish households. We compare how the new or changed practices of 21 households, learned during the intervention, have persisted through societal changes (i.e., the Covid pandemic and the energy crisis), and whether these new or changed practices helped households to deal better with these crises. In this way, we contribute to, and also reframe, the problem of evaluating long-term effects, and critically consider the persistence of small-scale interventions in practices.