Since refrigeration generally makes up about 8% of the average utility bill, ensuring optimal temperature settings can be a free and easy way to save energy. The freezer compartment should be between zero and 5°F; the refrigerator box should be between 37° and 40°F. If settings are 10° lower than these recommendations you can potentially increase energy usage by up to 25%. In order to monitor temperatures I recommend hanging a thermometer in the refrigerator and freezer compartments.