Every time the fridge door is opened, up to 30 percent of the cooled air can escape. The longer the fridge is open, the more your fridge has to work to cool again.
Even if you are closing your fridge doors, also make sure the door seal and gaskets on your refrigerator are properly maintained. If your fridge or freezer door is not sealing properly, it's leaking air and wasting energy. To test if the door seals are working, open each door and place a piece of paper on the seal, then shut the door. If the paper falls to the ground, you need to replace the seal.