Every home uses somewhere between 30%-50% of its energy to provide heating and cooling. Heating and cooling is controlled via a thermostat. For years DOE and others have advocated "Set Back" thermostats, to adjust temperature through the day depending on real occupancy - i.e. gone during work hour, make let the temperature go up during the summer and down in the winter. Interesting 4 out of 5 people with one of these thermostats don't really use them because they are too hard to remember how to set the parameters and controls.
A series of new thermostats are now on the market that let you use a web page to control settings. More advanced ones even let you change the settings from your phone or other locations. Having looked at several of the vendors out there, I don't really like any of them very much, at least for the average user. But one that works well for those of us that are really a big more geeky is Proliphix
