Title: It helps but don't expect miracles.
Review: I have been using 3 units for many months. My upstairs temperature varies quite a bit from the main floor. I have 2 of these units in one room and one in another. The room used to be about 6-8 degrees different than the main floor. I am guessing it is now more like 3-5 off. That is in the winter. I haven't used them in the summer with the AC yet.
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