For cooking and reheating food, microwave ovens are the most energy efficient. Most of the energy in a microwave oven is directed at heating the food directly and not the container the food is in.
By using a microwave to reheat or cook smaller portions, consumers can save up to 80 percent of the energy that would be used in a standard oven.
Convection ovens, which use a fan to circulate air inside the cooking chamber, are more energy efficient than standard ovens. Circulating the air not only helps food cook evenly, it also reduces cooking time and temperature, which saves energy. To get the most efficient use out of a convection oven, racks should not be covered in foil, as this blocks the flow of air and reduces the oven's effectiveness.
Ovens with a self-cleaning feature also use energy more efficiently. Due to the high temperatures used during the self-cleaning cycle, ovens with this feature have better insulation and a tighter door seal than standard ovens. This helps to contain the heat, making the cooking process more efficient. To help save on energy use, the self-cleaning cycle should be started after cooking a meal to take advantage of the remaining heat.