Portable and window air conditioners cool a single room, but they're built differently, and that difference shows up in how well they cool, how much they cost to run and how loud they are. The deciding question is usually simple: can a window unit fit your window?
If a window unit fits, it's usually the better choice: its hot side sits outdoors, so it cools more effectively for the power it draws and runs quieter in the room. A portable wins where a window unit can't go, such as casement windows, rental rules that forbid window units, or a unit you move between rooms.
How they differ
A window unit straddles the window sill: the cold coil faces the room and the compressor and hot coil sit outside. A portable keeps everything inside the room and pushes the heat out through a hose to a window kit. Keeping the compressor indoors, and moving heat through a hose, is where a portable loses ground.
Side by side
The table below lines up the two types on the points that decide most single-room purchases. Tap a column heading to sort.
Window vs portable room air conditioner, point by point
| Factor | Window unit | Portable unit |
|---|---|---|
| Where the heat goes | Compressor and hot coil sit outdoors | Compressor stays in the room; heat leaves through a hose |
| Cooling for the power drawn | Higher; little heat re-enters the room | Lower; the hose and cabinet leak heat back inside |
| Efficiency metric on the label | CEER | CEER measured against SACC |
| Noise in the room | Quieter; the compressor is outside | Louder; the compressor runs in the room |
| Installation | Lifts into a double-hung or sliding window and must be secured | Rolls in and vents through a window kit |
| Space used | Sits in the window; no floor space | Takes floor space near a window |
| Moving between rooms | Hard; must be dismounted | Easy; rolls on casters |
| Window types it fits | Double-hung or sliding | Also casement or crank, with the right kit |
| Draining water | Usually self-evaporates outdoors | Some models must be drained |
Cooling and efficiency ratings
Both are rated under federal test procedures, but the tests differ. Window units are rated by CEER. Portables are rated by CEER against a seasonally adjusted cooling capacity (SACC), a figure that accounts for the heat a portable leaks back into the room through its hose and cabinet.
Single-hose portables also exhaust room air, which pulls warm outside air in through every gap. A dual-hose design draws its cooling air from outside instead; see single-hose vs. dual-hose portable ACs. When comparing units, compare their CEER and the SACC or cooling capacity on the label, not only the headline BTU number.
Our air conditioner types overview lists the typical efficiency ranges each room-unit style falls into.
Running cost
Both cost the same to run per watt: watts × hours ÷ 1,000 × your rate. A unit drawing 1,000 watts for 8 hours a day for 30 days uses 240 kWh, about $43 a month at 18 cents per kWh.
A window unit usually delivers more cooling from those watts, so it reaches the set temperature sooner and runs less. Our portable AC electricity cost page has a calculator.
The difference is in the hours, not the per-watt price. As an example, suppose both units draw 1,000 watts.
If the window unit cools the room to setpoint and cycles off so it runs an effective 6 hours a day instead of the portable's 8, that is 1,000 × 6 × 30 ÷ 1,000 = 180 kWh, about $32 a month at 18 cents per kWh. That is roughly $11 a month less than the portable's $43, from the same 1,000-watt draw.
Installation
- Window unit: needs a double-hung or sliding window it fits, a secure mount or bracket, and someone to lift it into place. It blocks the window while installed.
- Portable: rolls into place and vents through a window kit, and works with some windows a window unit can't use. It takes up floor space, and its hose must stay short and straight. Some models need their collected water drained.
For awkward windows, see how to vent a portable AC without a window.
Noise
A window unit keeps its compressor outside the room, so the loudest part is outdoors. A portable runs its compressor inside the room, which you hear more, especially in a bedroom.
Which to choose
- Window unit: you have a double-hung or sliding window, want the most cooling for the power, and want a quieter room.
- Portable: your windows or lease rule out a window unit, you need to move it between rooms, or you want to avoid lifting and mounting.
If you are unsure, match your situation to the pick below.
| Your situation | Better pick |
|---|---|
| Double-hung or sliding window, want the most cooling and a quieter room | Window unit |
| Casement, crank, or awning window | Portable |
| Lease or HOA forbids window units | Portable |
| You move the unit between rooms | Portable |
| You can lift and mount it, and want the lower running cost | Window unit |
Size either one for the room with our BTU calculator.
Frequently asked questions
Is a window AC more efficient than a portable?
Usually. Its hot side is outdoors, while a portable loses some cooling through its hose and cabinet and, if single-hose, pulls warm air into the room.
Is a portable AC cheaper to run than a window AC?
Not usually for the same cooling. Both cost the same per watt, but a window unit typically needs fewer watt-hours to cool the same room.
Which is quieter, a portable or a window AC?
A window unit, in the room, because its compressor is outside.
Can I use a portable AC with a casement window?
Yes, with a window kit made for casement or sliding windows. That's one of the main reasons to choose a portable.
Do portable ACs cool as well as window units?
For the same room and the same power draw, a window unit usually cools more effectively, because its hot side is outdoors and little of that heat returns to the room. A portable loses some of its output through the hose and cabinet, and a single-hose model pulls warm air into the room as it exhausts. A correctly sized portable still cools the room; it just tends to run longer to get there.
Can a portable AC cool a whole room?
Yes, if it is sized for the room's square footage and the room is reasonably sealed. Because a single-hose portable draws replacement air in through gaps, its effective capacity is lower than its headline BTU, so do not undersize it. Size it with our BTU calculator, and see single-hose vs. dual-hose portable ACs for the infiltration difference.
Are portable air conditioners worth it?
They are worth it when a window unit cannot go in the window, when a lease or HOA bans window units, or when you need to roll the unit between rooms. If a window unit fits, it usually cools more effectively for the power and runs quieter in the room. The choice is mostly about your window and your rules, not raw performance.
How long do window and portable ACs last?
The U.S. Department of Energy puts a room air conditioner's service life at about 10 to 15 years. A window unit is a room air conditioner, so expect that range with regular filter cleaning. A portable uses the same basic compressor and refrigerant circuit, so plan on a broadly similar lifespan.