16 hours ago, Ashen said:I think the only benefit is that a smaller amount of warm air is allowed to enter the unit if it is kept full, applies to upright models obviously. As cold air drops out the bottom warm air is drawn in, and has to be cooled down once the door is closed. If you have an EnergyStar Rated appliance I really wouldn't worry about the minimal savings you would get unless you are opening and closing your fridge excessively .
That's the folk wisdom, but it doesn't turn out to be a big deal. The amount of thermal mass of the air in the fridge is minute ... it takes very little energy to chill a few cubic feet of air from room temperature to 30-something.
If you calculate the thermal mass, of say, 20 cubic feet of air, and look at the amount of energy it takes to raise it from 4°C to 22°C, it's equal to 0.0004 kilowatt hours. If you assume a refrigerator isn't that efficient, and takes twice as much energy to cool that air back the other way, you've got .0008 kwh. At our current price of 19.2 cents per kwh in NYC, this is 0.015¢ to open the door and let out every molecule of cold air.
So it should go without saying that it makes no difference if you open the door for 5 seconds or half a minute. You use more energy putting in a jug of room temperature water and letting the fridge cool it.
