We have a 29' 5'er (2005 model, but new to us) with ducted AC. It's been plugged in since the day we brought it home, with the thermostat set on about 82ish. For now, it's sitting in the wide open, baking in the sun and temps are in the upper 90's during the afternoon. The AC runs mostly "on" during the afternoon, but doesn't appear to have any trouble maintaining that temp setting. We've set it cooler, and it did fine then too. A lot of it depends on how cool the starting temp is. If you turn the AC on and it's 95 degrees in the unit, then it's going to struggle. If you can reach a desirable temp and leave it set on that, you should be better off.