Abstract: The substantial increase in residential electricity demand over the last century challenges public policies aiming at energy conservation. Many researchers nowadays agree that current levels of consumption are unsustainable and that a reduction in "standards" is inevitable. We argue that in this context, attention should be devoted to the "naturalistic" basis of consumer practices. By this we mean the basic human wants involved in household activities, as well as modes of consumer learning. Using the case of clothes washing as an example, we show how consumption externalities and knowledge progress interact with the emergence of social norms. We argue that the cleanliness norm emerged in the 19th century for a fundamental reason: it helped to solve the problem of the spread of infectious diseases, which figured prominently in times when social networks radically changed during urbanization and industrialization. The social significance of cleanliness is thus not arbitrary. Placing the naturalistic underpinnings of consumer behavior on the agenda complements the constructivist view on cleanliness and helps to inform policy-making heading for a change in standards.