Window AC vs portable AC: which costs less to run?

All numbers use the April 2026 US residential average of 18.05¢/kWh from the EIA Electric Power Monthly. Wattages are full-draw figures for standard non-inverter models.

8,000 BTU (bedroom, 250 to 350 sq ft): Window unit at 750 watts costs $0.14 an hour, or $32.49 a month at 8 hours a day. Portable at 900 watts costs $0.16 an hour, or $38.99 a month. The portable adds $6.50 a month.

10,000 BTU (living room, 350 to 450 sq ft): Window unit at 900 watts costs $0.16 an hour, or $38.99 a month. Portable at 1,200 watts costs $0.22 an hour, or $51.98 a month. The portable adds $13 a month.

The gap is smallest at 8,000 BTU because compact portable models at that size are relatively efficient. At 10,000 BTU, where most of the market sits, the gap widens to $13 a month or $52 over a summer. The full per-size breakdown for each type is in the window AC running cost and portable AC running cost posts.

The monthly gap scales directly with your state rate. Cheap electricity narrows it. Expensive electricity stretches it. All figures below are a 10,000 BTU unit running 8 hours a day for 30 days at full draw.

Louisiana (11.9¢/kWh): Window $25.70, portable $34.27. Gap: $8.57 a month.

Texas (14.8¢/kWh): Window $31.97, portable $42.62. Gap: $10.66 a month.

Florida (15.1¢/kWh): Window $32.62, portable $43.49. Gap: $10.87 a month.

New York (22.3¢/kWh): Window $48.17, portable $64.22. Gap: $16.06 a month.

California (31.4¢/kWh): Window $67.82, portable $90.43. Gap: $22.61 a month.

Hawaii (41.2¢/kWh): Window $88.99, portable $118.66. Gap: $29.67 a month.

Over a four-month summer in California, the portable costs $90 more than the window unit. In Hawaii, $119 more. In Louisiana the full summer gap is only $34, low enough that the convenience of a portable may be worth the tradeoff. The electricity rates by state page has the current rate for every state, and the window AC calculator and portable AC calculator run the math at your local rate.

A window unit mounts through the window with the condenser (hot side) outdoors and the evaporator (cold side) indoors. Heat flows out directly. The room stays sealed.

A portable AC sits entirely inside the room. It pumps heat into an exhaust hose that vents through a window panel. Three things work against it. First, the hose itself radiates heat back into the room, undoing some of the cooling. Second, single-hose models (most of the market) push room air out through the exhaust, which creates negative pressure that pulls warm outside air in through every gap around doors and windows. Third, the condenser coil sits indoors surrounded by the air it is trying to cool, so it works harder than a coil sitting in outdoor air.

The efficiency difference shows up in the numbers. At 10,000 BTU, a window unit draws 900 watts. A portable draws 1,200 watts. That is 300 extra watts every hour for the same cooling output. Per the DOE Energy Saver, room air conditioner efficiency is measured in EER (energy efficiency ratio): BTU of cooling per watt drawn. A typical window unit lands at EER 10 to 12. A typical single-hose portable lands at EER 8 to 10. That gap is the 25 percent cost difference on the bill.

Portable ACs exist because of installation constraints, not because anyone prefers paying more. The situations where a portable is the right call:

Rental restrictions. Many landlords and lease agreements prohibit window units. Some buildings in New York, San Francisco, and Chicago ban window AC brackets outright through building codes or co-op board rules.

HOA rules. Homeowner associations in condos and townhouses frequently ban visible window units for aesthetic reasons. A portable exhausts through a flat window panel that is less visible from outside.

Casement or sliding windows.Standard window ACs require a double-hung window. Casement windows (the kind that crank open sideways) and horizontal sliders will not accept a window unit without an expensive custom bracket. A portable's exhaust hose fits through the opening of almost any window type.

Multi-room flexibility. A portable rolls between rooms. A window unit stays put. One portable running 8 hours a day between two rooms costs $52 a month. Two window units covering the same two rooms at 4 hours each cost $39 combined, but require two purchases and two installations.

If none of these apply and a window is available, the window unit wins on running cost every time. The fan vs AC comparison covers the even cheaper option when the temperature allows it.

The 25 percent cost penalty is baked into the physics, but three moves cut it down.

Seal the window panel. The foam seal that ships with most portable ACs leaks. Warm air seeping in around the panel forces the compressor to run longer. A $15 to $25 rigid seal panel or weatherstripping tape can cut compressor runtime 10 to 15 percent, saving $5 to $8 a month at the national average.

Consider a dual-hose model. Dual-hose portables pull outdoor air to cool the condenser instead of using room air. This eliminates the negative-pressure problem entirely. Dual-hose models cost $100 to $200 more upfront but use 20 to 40 percent less electricity than single-hose models for the same cooling. At the national average, that saves $10 to $20 a month, so the upfront premium pays back in one to two summers.

Use a timer or thermostat mode. Running the unit only while someone is in the room drops hours from 8 to 5 or 6. That alone cuts the monthly bill from $52 to $32 to $39.

The full set of portable-specific savings levers is in the portable AC running cost piece. For summer bill tactics that work across all cooling types, the summer electric bill guide covers the rest.

To run the math at your wattage and your state rate, use the window AC calculator or the portable AC calculator. The per-type deep dives cover everything from duty-cycle adjustments to inverter savings: window AC running cost and portable AC running cost. The broader cooling comparison including fans and central AC is in fan vs air conditioner cost.