Comment by nkrisc

You’re only losing cold air, which has very little mass compared to what you’re actually storing in your fridge. The energy cost to re-chill the air in the unoccupied volume of your fridge can’t be that significant, I’d imagine.

It’s be an interesting experiment to put a temperature probe in something like a block of cheese, let it cool to the ambient fridge temperature, then open the fridge door for a few minutes and see if the temperature of the cheese even measurably changes over the next few hours or whatever amount of time.