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I think it can be compared to using a celing fan. During the summer it blows cold air down at you and you feel cooler because of the wind chill factor. During the winter it can be reversed to slowly rotatet the air up and then down the sides of the walls. It must be done slowly so it does not create any noticeable wind chill factor, as it will make the air feel cooler. Slowly mixing the air evenly is known to save energy during the heating season. Energy Star: Using the Ceiling Fan Year Round It should not matter how you mix the air as long as it is done slowly. Kari measured as much as 5 C difference between floor and 3 feet up. I would think that in particulare a house with cold floor will benefit from mixing the air, as this will probably be where the highest difference is in vertical temperature. If mixing the air will help you lower the average temperature in the room with 5 C then the saving would be as if you turned down your thermosate with 5 C, which should give a noticeable difference on your heating bill.