In the global context of reducing carbon emissions and shifting towards sustainable modes of urban infrastructure, strategies that provide decentralized access to renewable energy technologies for the urban poor are increasingly promoted. However, while innovative energy technologies are introduced in order to support global targets for sustainability and service-delivery while also directly benefiting low-income households (e.g. by reducing the monetary costs of energy), there is widespread evidence that low-income urban dwellers do not always readily accept these technologies. Typically, the urban poor are blamed for failing to adopt new technologies, with little consideration for underlying socio-cultural causes. Using examples drawn from qualitative research in low-income settlements in Mumbai and Cape Town, this paper demonstrates the role of socio-cultural attitudes and practices in affecting social acceptance of domestic solar energy interventions. Focusing specifically on perceptions of normality and practices of social capital, both of which are connected to collective social influence, the paper reveals how these concepts affect the socio-cultural acceptance of new energy technologies amongst low-income urban dwellers in the global South. Furthermore, we argue that adopting a socio-cultural perspective is a crucial, but often overlooked, aspect of scholarly and policy analyses of, and strategies for, energy transitions in the global South.