Saving energy > Cooking Select the right pan or appliance. Oversized pans waste energy. The pan you use should match the burner size. When boiling foods, keep the amount of water used to a minimum. Using excess water that must be heated wastes the energy required to raise its temperature. Keep lids on pans as you cook; cooking without them can require three times as much energy as cooking with them on. Look for pans with glass lids if you like to keep an eye on what you are preparing. Cooking temperatures can drop as much as 25º celsius every time the oven door is opened, causing the oven to reheat. If it's not necessary, don't peek. Defrosting frozen foods in the refrigerator will reduce cooking time. But allow enough time for defrosting to take place.