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Types of air conditioner come in a small set of shapes, and the right one for a home depends on the space, the window or wall available and whether the home already has ducts. A window unit sits in a window opening and cools the space beside it. A portable unit rolls on casters and vents hot air outside through a hose in a window. A ductless split pairs a quiet indoor unit with an outdoor compressor, and a central system cools the whole home through ducts.
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The quick answer
The short version: a window unit suits a single space with a suitable window; a portable unit suits a rented home; a ductless split suits a home without ducts; a central system suits a home that already has ducts; and a through-the-wall unit suits a wall that can take a sleeve. The table below sets the types side by side.
| Type | How it cools | Where it fits | Watch for |
|---|---|---|---|
| Window | Sits in a window opening and blows cool air into the space | A space with a window that can hold the unit | The window stays blocked |
| Portable | Rolls on casters and vents hot air outside through a hose | A rented home | The hose needs a window to vent through |
| Ductless split | An indoor unit on the wall pairs with an outdoor compressor | A home without ducts | The indoor unit needs a wall spot and a line outside |
| Central | Cools air at a central unit and moves it through ducts | A home with ducts | Ducts must be in place and in good shape |
| Through-the-wall | Sits in a sleeve through an exterior wall | A wall that can take a sleeve | The sleeve is a permanent opening in the wall |
Window air conditioners
A window air conditioner is a single box that holds the compressor, the fan and the cooling coil in one case. It slides into a window opening, with the front inside and the back outside, so heat leaves through the back of the unit. The unit rests on the sill, side panels close the gaps at the edges, and the unit plugs into a household outlet. That simplicity is why window units are common in rented homes and in spaces that need cooling for part of the year. The trade-off is the window itself: while the unit is in place, that window cannot open, and the unit blocks light.
Portable air conditioners
A portable air conditioner is a floor unit on casters that can move from space to space. It pulls warm air from the space, cools it and sends the heat outside through a hose that fits in a window. Because nothing is fixed to the window or the wall, a portable unit suits a rented home or a space where the window cannot hold a window unit. The hose is the part to plan around: it must reach a window, and the window kit must fit that window, or the hot air has nowhere to go. Portable units also sit inside the space they cool, so the compressor sound stays in the space with the listener.
Ductless split air conditioners
A ductless split, also called a mini-split, has two parts: a slim indoor unit that mounts high on a wall and an outdoor compressor that sits outside the home. A narrow line through a small opening in the wall carries refrigerant between them, so the compressor stays outside while the indoor unit moves cool air through the space. That split is why these units run quietly indoors and why they suit a home without ducts: each indoor unit cools the space it serves. A split needs a wall spot for the indoor unit, a place outside for the compressor and a line between them, and the work calls for a licensed installer to fit the line and charge the system. The indoor unit stays on the wall through the year, so it suits an owner who wants a permanent fixture.
Central air conditioners
A central air conditioner cools air at a single central unit and moves it through ducts to vents in each space of the home. The outdoor compressor and the indoor coil work as one system with the ductwork, so the whole home cools together and the only parts visible inside are the vents and the thermostat. That even cooling is why central systems suit a home that already has ducts. A home without ducts faces a larger job, since ducts must be added through the attic, the walls or the floor before a central system can serve the home. Central cooling runs as one system, so it cools the whole home rather than a single space.
Through-the-wall air conditioners
A through-the-wall unit is close kin to a window unit, with one difference: it sits in a sleeve set through an exterior wall rather than in a window opening. The sleeve stays in the wall through the year, and the unit slides in and out of the sleeve, so the window stays free and the wall carries the weight. That shape suits a space where the window must stay clear. The sleeve is a permanent opening in the wall, so the wall must suit it, and the unit needs clear air outside for its back.
Can a UPS or power station run an air conditioner?
An air conditioner is a heavy load, and the backup gear in the reference listings is built for lighter loads. The largest UPS in the reference set, the CyberPower CP1500PFCLCD, is a 1500VA/1000W unit with 12 outlets and a 3-year warranty, built to keep computers, workstations and network gear running through an outage. The APC BE600M1 gives 23 minutes of runtime at a 100W load. The GOLDENMATE lithium UPS (on Amazon) in the same set holds a 153.6 Wh battery at 1000VA/600W, again a computer-scale unit. Those figures show the scale: a UPS of this class carries a computer and a router through a short outage, not an air conditioner through a warm afternoon. A portable power station built for an air conditioner is a different class of gear, with a larger battery and a higher continuous output. Read the running watts and the starting watts from the label, measure the draw with a watt meter, and match the station to those figures. See the best portable power stations for an air conditioner and the inverter versus UPS guide.
How to choose among the types of air conditioner
Work through the home first, then the power.
- Start with the opening: a window that opens and can hold a unit points to a window unit; a wall that can take a sleeve points to a through-the-wall unit; no opening at all points to a portable unit with a hose kit.
- Count the spaces: a single space points to a window, portable or split unit; a whole home with ducts points to a central system; a home without ducts points to a split.
- Check the power: read the running watts and the starting watts from the label, and measure the draw with a watt meter before planning backup power or a generator.
- Mind the install: a window or portable unit needs no permanent work, while a split or central system needs a licensed installer and stays in place through the year.
- Mind the sound: the compressor sits outside on a split or central system, while a window or portable unit keeps it in the space.
FAQ: power away from the grid
Can a UPS run an air conditioner?
No, not the desktop UPS units in the reference listings: the largest, the CyberPower CP1500PFCLCD at 1500VA/1000W, is built for computers and network gear, and the APC BE600M1 gives 23 minutes at a 100W load. An air conditioner needs a power station or generator sized to its running and starting watts. See whether solar power can run an air conditioner.
Which type of air conditioner works without ducts?
A window unit, a portable unit and a ductless split all cool without ducts. A central system needs ducts, so a home without ducts should look at a split.
Do portable air conditioners need a window?
Yes, in most cases. The hose that carries hot air outside must vent through a window with a kit that closes the gap, or through another opening to the outside. Without a vent, the hot air stays in the space.
Can solar power run an air conditioner?
Yes, with a large enough power station and enough panels. Read the running and starting watts from the label, measure the draw with a watt meter, and size the station and the panels to those figures. See the power station versus gas generator comparison for air conditioners.
Which type suits a rented home?
A portable unit, since nothing is fixed to the window or the wall and the unit moves out with the renter. A split or central system is a permanent fixture, so it suits an owned home.
Related solar guides
See the best portable power stations for an air conditioner, solar air conditioner versus solar fan, the best watt meters and all controllers and inverters guides.
