Home sensing and automation systems are rarely discussed with reference to their direct energy demand, much less other environmental impacts such as greenhouse gas (GhG) emissions arising from their manufacture and transport. It is imperative that designers of such systems understand the impacts of the technologies they introduce, particularly where intended to save energy and promote sustainability. Using four case studies drawn from recent Ubicomp and HCI literature, this reflective paper quantifies the direct energy and estimates the embodied emissions arising from specific installations of home sensing. We contextualise this by comparing with typical impacts arising from existing ICT devices commonly found in the home, and highlight a number of ways in which designers can reduce the impacts of the systems they introduce into the home.