Decision-making is a central component of every facet of human life, and is generally understood to be either conscious (deliberate) or automatic (non-deliberate). There has been little research to date on decision-making in the context of domestic energy consumption. Our study elucidated the human processes related to decisions around domestic energy use. In particular, the study investigated the neural and cognitive triggers of decision-making which differentiate between optimal and non-optimal energy consumers. Using EEG (electroencephalography) to assess brain function, we investigated brain activity associated with decisions around energy consumption and in this paper we report results from a study of 30 participants for whom we recorded their neural activity as they made decisions. As well as this, behavioural data related to cognitive processes involved were recorded. By examining this data, we aim to clarify some of the reasons why people make certain decisions about domestic energy consumption.