Staying warm. In the winter, I used to stay warm by turning up the thermostat. Then I discovered (via HN) the Low-Tech Magazine article, "Insulation: first the body, then the home." [0] The article argued that it's much more efficient to focus on heating yourself rather than your whole living space. I invested in high-quality wool clothes that I wear in layers and warm slippers. Now, I keep my home about 5 degrees F…
I don't like wearing big layers of clothing. I like being in a very light t-shirt. I'm happy to pay the extra cost to heat the room I'm in with a space heater in the winter time.
(But if you've got some kind of super-insulated house, then never mind.)