If you want an air conditioner that does not require an exhaust hose or any kind of vent to the outside, you're in for a shock. It does not even exist, at least not yet anyway!
All air conditioning units must be vented to the outside to get rid of the excess moisture and hot air they produce. That's right!
AC produces a lot of hot air as well as cold.
The only reason you don't notice is because the hot, moist air is vented to the outside either through the wall via discrete piping that connects to an external extraction unit (typically mini-split systems and fixed AC), or through a flexible plastic hose connected to a window fixing kit from a portable unit.
Ventless Cooling Devices
That doesn't mean you can't have a cooling appliance that doesn't need to be vented to the outside.
It's not an air conditioner as most people are familiar with, but an evaporative cooler (sometimes called a swamp cooler).
They bear a close resemblance to regular portable air conditioners as the image to the right shows, but they certainly don't create cold air in the same way.
In fact, these coolers work in a completely different way to the refrigeration system in an AC unit.
How They Work
They create cool air by evaporating moisture in the same way your skin feels cold when you perspire when you're hot and a breeze chills your body down.
It's not the breeze that cools you directly, but the evaporation of your perspiration that chills your skin!
The big difference owners of swamp coolers notice between their coolers and AC is that first, there is no hot air produced by the process, therefore there is no need for an external vent hose or exhaust ducting.
Second, the energy consumed by a swamp cooler is a small fraction of AC (typically 1/20th as much). That can be a significant saving in energy and a surprising source of relief when the periodic electricity bill arrives!
One last note on the resemblance issue, portable swamp coolers are often referred to as "ductless or ventless portable air conditioners," but again, they're really not AC at all.
Swamp Cooler Economy
The reason swamp coolers use so little electricity to produce so much cold air is because there is no energy hungry processing going on inside the unit. The only sizable energy user is the fan, which is generally less than 100 watts for most room size units.
All other electrical use goes on the control panel, which is negligible. So you can see these cooling appliances are very economical to run yet still produce a lot of useful cold air to keep you cool and reduce the temperature in the room you are occupying.
Humidity: The Swamp Cooler Achilles Heel
While they are great for keeping you cool, have no need of venting and cost almost nothing to run, you might be thinking that this is the almost Utopian alternative to the energy hungry and complicated air conditioning setup.
Unfortunately, there is a major downside to swamp coolers and that is their inability to work in very humid conditions.
Of course, they still push out a lot of wind no matter what the climate because of the internal fan, but the evaporation process that produces cold air is reduced considerably when the air is already laden with moisture (humidity).
This can be simply explained as follows:
To create that cold air typical of a cooler, an evaporative unit needs the air to be fairly "dry" in order to absorb the cold, moist air the unit expels. As long as the air is continually recycled by having a window open to let in drier air from outside, the swamp cooler will keep producing its cold breeze.
But if the air is heavy or even saturated with moisture because the room is sealed shut (all windows and doors closed) or the atmosphere is naturally humid in the area you live in, the cooling by evaporation process cannot work. That's because saturated air cannot absorb any more moisture and so the cooling effect is greatly reduced until the humidity level reaches 100% and the cooling effect ceases altogether.
This is similar to what happens when you are, for example in a very hot and humid place without air conditioning and no matter how hard you blow a fan at yourself, you just don't feel any cooler. You are probably perspiring profusely, but it is not cooling your skin any.
Where Do You Live?
So I hope you can now see where the effectiveness of an evaporative cooler can fall down if you experience a generally high moisture level in the air in your area. But if you live in a low humidity area, you're in luck because a swamp cooler can definitely work to keep you as cool as AC but without the cost or the need for venting.
The best way to find out if your area is best suited for this kind of indoor climate control is to call your local weather station or check online. As long as the humidity level is below about 50%, you'll be able to enjoy the benefits of evaporative cooling.