FWIW, you are correct that it is essentially physically impossible for the single hose models to be as efficient as dual hose. Single hose models take in condit

FWIW, you are correct that it is essentially physically impossible for the single hose models to be as efficient as dual hose. Single hose models take in conditioned air, pump heat into it, then pump that air to the exterior. Dual hose do the same, but with exterior air as the input. Single hose models have to work harder two ways. First, in pumping the air out of the conditioned environment, they're basically throwing away work they've done. Not all of it, but some. More the bigger the difference is between the interior and exterior. Another thing they have going against them is that they need to pull air from somewhere -- the exterior. So their fans have to work a bit harder due to the pressure difference. Dual hose models suffer neither drawback. Single hose portable ACs are an abomination that should not exist.