fair enough, yes, I've experienced many a washer-dryer, and they don't work. Maybe there are some condensing models that do actually work then. When you consider the efficiency of a building, you consider the building itself, how it is heated and how 'leaky' it is. I'm interested in the costs associated with gas space heating a conventional house, which can be astronomical. The number of appliances plugged in is neither here nor there, it's not something that you can control. You can control things like lighting and the need for cooling/ventilation by careful design, and considering how people will adapt the house.