Internet use and online services underpin everyday life, and the resultant energy demand is almost entirely hidden, yet significant and growing: it is anticipated to reach 21% of global electricity demand by 2030 and to eclipse half the greenhouse gas emissions of transportation by 2040. Driving this growth, real-time video streaming (‘watching’) is estimated at around 50% of all peak data traffic. Using a mixed-methods analysis of the use of 66 devices (e.g. smart TVs, tablets) across 20 participants in 9 households, we reveal the online activity of domestic watching and provide a detailed exploration of video-on-demand activities. We identify new ways in which watching is transitioning in more rather than less data demanding directions; and explore the role HCI may play in reducing this growing data demand. We further highlight implications for key HCI and societal stakeholders (policy makers, service providers, network engineers) to tackle this important issue.