The problem with the portable units on wheels is that they radiate heat from the cabinet since the whole thing is inside. That hot air exhaust hose that you are supposed to stick out a window does not remove all the heat. You are basically sitting next to a little radiator that is trying to remove heat from the space it is radiatively heating. These things are only good if you are sitting with your face in front of the vent...
Cut the BTU output number in half on these, and you probably are getting about that.
5K BTU window units work pretty well cooling small spaces, and can sometimes run on a 1000W genny, depending on the startup surge and the capability of the genny to handle it.
