My son has a small window unit. His duct run is ridiculously long and the main unit has never sufficiently cooled his room so I bought him one. And he has two computers and two game systems and one large TV constantly running and he gets the direct afternoon sun with brick on the outside. I get jealous when I go in there it's nice and freezing like I like it. I'll come in from working outside and stand in front of his AC to cool off. I saw zero increase in my power bill. I think the packaging estimated like $25/year to operate it.That’s why we got a window unit for the bedroom. We can leave the ac higher in the rest of the house, close the bedroom door at night and crank the window unit down to subzero. I was surprised at how quiet the new units are, and how much $$ we saved on the electric bill!