The problem with these units is that whilst they shove cooled air out the
front, they also throw out lots of heat from the rear and chuck your
expensively cooled and then heated air out the pipe. They are an
environmental disaster and should be banned.

This last may be true but it's not "these units". All aircon works like
this!

Not at all. Other types of air con units don't do this. Because:

(a) The back (condenser) is outdoors so can shove out as much parasitic heat
as it likes without affecting the building.
(b) The air actually heated by the condenser and released through the outlet
comes from outside. Expensive interior cold air is not used for this
purpose.

Basically, running a single pipe portable air conditioner causes as much
baking hot air to come in from outside as it pumps outside through its hose.
A split system actually provides no ventilation at all, so doesn't let hot
air into the house. A sophisticated building system may be designed provide
controlled heat recovery ventilation.

Some portable air con units can be modified by attaching an additional hose
with duct tape to the inlet grille, so that outside air is used on the
condensor. However, not all units can be so modified, as the supply for the
evaporator (inside air that comes cold out of the fan) must be interior air,
so this is only possible if the supply for each function comes from a
different grille.

Christian.