This article at http://www.building4change.com/page.jsp?id=1444 on “Whole house shutdown” says that:
Technology to turn off power to non-essential electrical items while residents sleep or are out can have major impact
A system that allows home occupants to conveniently and reliably turn off power to non-essential electrical items while they sleep or leave the house could cut household CO2 reductions by almost a fifth. This finding emerges from a study of technologies that could influence a reduction in energy consumption and associated CO2 emissions for a typical home built in 2016, carried out by NHBC Foundation.
From the nine technologies assessed, a system to remove power from all non-essential electrical items, called ‘whole house shutdown’, offered the greatest CO2 savings of 19 percent. The study also identifies individual socket shutdown units and waste water heat recovery as other technologies that can offer significant CO2 reductions of 16 percent and almost 7 percent respectively.