It depends on the specific refrigerator. For instance, an older fridge from the 80s with a capacity of 20 cubic feet costs about $14 to $20 a month to run. On the other hand, a brand-new Energy Star refrigerator of the same size might cost only $2 to $8 a month to run. Most new refrigerators come with a label that gives you an estimated cost to operate them for over a year.