Changes in energy use have been a key part of many dramatic social, economic and environmental changes during the twentieth century and before, making energy interesting to environmental historians. Today, policy makers seek reductions in energy use and carbon emissions to mitigate climate change through demand management policies that attempt to reduce usage or shift it in time away from peak demand. To understand the impact of such policies it is necessary to understand both how they were promoted and received. This article discusses electric heating in early post-war Britain, which was seen as a particularly problematic energy use, as electric fires were used at peak times. The Electricity Development Association (EDA) tried simultaneously to reduce undesirable peak demand while encouraging increased demand more generally. In the late 1940s it advertised against peak use of electric fires, whereas in the 1950s and 1960s it instead concentrated on promoting off-peak heating appliances, first under-floor heating and then block storage heaters. I will analyse how the London County Council and its tenants adopted and adapted electric underfloor heating, illustrating the complicated way demand is made and unmade. The paper concludes that, while demand management has been attempted by the electricity industry since well before the 1970s, these attempts only had a limited effect on the overall trend towards increasing demand, in part to do with how these promotions were adopted.