Freezer (and fridge) are designed to keep the inside content cool. But it’s funny to realize that most of the content is air. Each time you open the freezer you force to move the inside air with the outside… and the inside temperature rises. How can we avoid it? Keeping a lot of things, in order to minimize the air’s volume. This way the freezer doesn’t “complain” (activates the compressor of the freezing gas) every time the door is opened (even for taking pictures). I’ve chosen water bottles because it’s quite easy item to get at home, but if you can get some concrete blocks or solid bricks, you’ll get an even better result.
With some energy-saving bulbs, this idea and some more ideas, my electricity bill is only 13€ per month.