A portable A/C unit with one hose uses some of the cooled air from inside the house and vents it outside to cool the condenser. Warm air from outside will be "sucked" in through cracks in the house. This creates a thermal inefficiency.

A two hose system (if I understand correctly) uses one hose to bring the air into the unit for cooling the condenser only. The air then exits through the other hose. None of the cooled air from inside the house is being pushed out. In other words, the air that the 1 hose system "sucked" in through cracks in the house is pulled in through a hose and completley separated from the inside air of the house. This makes this two hose system thermally more efficient and cheaper to run.

My question is though, how much of a difference does this make?

I have a need to cool down one room in my house that is always hot in summer. When the other living space is at a comfortable level, this room is hot. The windows in this room are crank style windows, so I cannot use a window air conditioner or put hoses through the window. I will have to cut holes through the wall.

Should I go with a two hose portable A/C unit which would require cutting two holes through the wall or is a one hose unit "good enough", saving me from cutting two holes through my house?

Thanks for any replies.