One thing I have learned since we installed an electricity monitor in our home, is that I really had now idea which appliances were using the most electricity. Several years ago we installed compact florescent bulbs in the house to reduce our electricity usage. That did help, but I’ve discovered that we would have saved a lot more energy if everyone had simply shortened their daily showers by a couple of minutes. Taking a shorter shower would not have cost us any money (those compact florsent bulbs were very expensive 8 years ago), but as a family we would have used significantly less energy.
The same principle holds true when building or renovating a home. I never would have guesses that carpeting is several orders of magnitude more energy intensive to manufacture and install than ceramic tiles or hard wood floors. The 8 Minute TED Talk video below by Catherine Mohr provides some great non-intuitive examples from her home building project: