This unit ran for three days in one room and it wouldn't drop below 79 degrees. The room is approximately 400 square feet and it was certainly cooler, but I found that the unit didn't do any better than the small, old window unit it replaced. I gave it a three because in all fairness, I never tried the heater or dehumidifier. FYI I did add water to the tank and I had drained any condensation from the unit.