Window vs portable air conditioner: running cost

These two are usually sold as equivalent, with the portable priced as the convenient option. On the meter they are not equivalent, and the reason is in how a single-hose design works. At the US average rate of 18.34¢ per kilowatt-hour the gap is $32 a year.

All comparisons · Both figures from the same duty-cycle model · EIA June 2026

Window air conditioner costs less by

$32a year

$323 over ten years · window air conditioner uses 23% less electricity

Window air conditioner 596 kWh a year against 771 kWh — at the US average rate of 18.34¢/kWh.

Window air conditioner596 kWh$109
Portable air conditioner771 kWh$141

The verdict

The window unit wins, and the gap is larger than the wattage difference suggests. A single-hose portable exhausts indoor air outside, which puts the room under negative pressure and drags unconditioned outside air in through every gap in the building. It is cooling air that it is simultaneously replacing with warm air, so it runs at a higher duty cycle and never quite catches up. Real-world capacity is commonly a quarter to 40% below the label.

Side by side

Window air conditioner and portable air conditioner are costed by the same function from the same dataset, so the $32 between them is a difference in the appliances and not in how each was measured. Window air conditioner draws an average 541 W across the hours it runs; portable air conditioner draws 771 W across its own.

Both at 18.34¢/kWh, the EIA residential average for June 2026. Ten years is roughly the service life of either.

Window air conditionerPortable air conditionerDifference
Electricity a year596 kWh771 kWh176 kWh
Cost a year$109$141$32
Cost a month$9.10$12$2.69
Over ten years$1,092$1,415$323

The assumptions behind those figures

Nothing above is a manufacturer’s claim. 900 W at 60% for 10 hours a day, 110 days a year, is where window air conditioner’s 596 kWh comes from; 1,100 W at 70% for 10 hours over 100 days is where portable air conditioner’s 771 kWh comes from. The duty cycle is the input most published comparisons leave out, and it is why the ratings and the running costs are not in the same proportion here.

Change any of these on the appliance’s own page and every figure moves with it. The duty cycle is a property of the machine; the hours are a property of you.

Window air conditionerPortable air conditioner
Rated power900 W1,100 W
Duty cycle60%70%
Hours a day in service1010
Days a year110100
Average draw while in service541 W771 W

What the gap is worth at your rate

Nothing here is a purchase decision, so there is no payback to compute. But $32 is the gap at the national average, and what it is worth to you depends on your rate — which varies more across the country than the difference between these two.

Residential average for June 2026, from the EIA. Your own tariff may differ; you can read it off your bill.

Window air conditioner
$109

a year

Portable air conditioner
$141

a year

A year apart
$32
Over ten years
$323

In the US average at 18.34¢ per kWh. Both figures on the standard assumptions printed above; your rate is the input that moves the gap most.

The gap in your state

The appliances are the same everywhere; the rate is not. The gap between these two is worth $93 a year in Hawaii and $23 in Nevada — 4× apart, on identical appliances.

A year of each, by state. Residential average price, EIA June 2026.

StateRateWindow air conditionerPortable air conditionerDifference
Hawaii52.72¢$314$407$93
California34.74¢$207$268$61
Massachusetts29.61¢$176$228$52
Maine29.59¢$176$228$52
New York29.49¢$176$227$52
Rhode Island29.23¢$174$225$51
Alaska28.21¢$168$218$50
New Hampshire27.01¢$161$208$47
New Jersey24.95¢$149$192$44
Vermont24.44¢$146$189$43
District of Columbia24.39¢$145$188$43
Connecticut24.32¢$145$188$43
Michigan22.99¢$137$177$40
Maryland21.84¢$130$168$38
Pennsylvania21.73¢$129$168$38
Illinois19.89¢$118$153$35
Wisconsin19.56¢$116$151$34
Delaware19.29¢$115$149$34
Ohio19.19¢$114$148$34
Minnesota17.52¢$104$135$31
Indiana17.51¢$104$135$31
Virginia17.22¢$103$133$30
Colorado17.13¢$102$132$30
Alabama16.4¢$98$127$29
Georgia16.36¢$97$126$29
Oregon16.32¢$97$126$29
Missouri16.22¢$97$125$29
Texas15.94¢$95$123$28
Iowa15.93¢$95$123$28
Kansas15.71¢$94$121$28
South Carolina15.55¢$93$120$27
West Virginia15.45¢$92$119$27
South Dakota15.36¢$91$118$27
Wyoming15.24¢$91$118$27
Arizona15.18¢$90$117$27
Montana15.14¢$90$117$27
Florida15.1¢$90$116$27
New Mexico15.06¢$90$116$26
Washington14.91¢$89$115$26
Mississippi14.88¢$89$115$26
North Carolina14.74¢$88$114$26
Idaho14.37¢$86$111$25
Oklahoma14.33¢$85$111$25
Kentucky14.26¢$85$110$25
Arkansas14.12¢$84$109$25
North Dakota14.12¢$84$109$25
Tennessee14.07¢$84$109$25
Louisiana13.49¢$80$104$24
Utah13.37¢$80$103$24
Nebraska13.25¢$79$102$23
Nevada13.11¢$78$101$23

Questions

Is a portable air conditioner more expensive to run than a window unit?
The window unit wins, and the gap is larger than the wattage difference suggests. On the assumptions printed above, window air conditioner costs $109 a year and portable air conditioner costs $141 at 18.34¢ per kilowatt-hour — a difference of $32 a year, or $323 over ten years at today’s rate.
How is window air conditioner’s 596 kWh a year calculated?
Rated watts × duty cycle × hours × days, plus standby, times your rate — the same function that produces every figure on this site. For window air conditioner: 900 W × 60% × 10 h × 110 days ÷ 1,000 = 596 kWh, which at 18.34¢ is $109. Portable air conditioner runs through the identical arithmetic on its own assumptions and lands at $141. The rate is the EIA residential average for June 2026; nothing here is a manufacturer’s claim.
Why is the BTU rating not the whole story?
BTU is cooling capacity and watts is what you are billed for; the ratio between them is the efficiency rating. Divide BTU by CEER to get the draw. Two units with the same BTU can differ substantially in what they cost to run, and a portable that cannot achieve its rated capacity in practice is worse still.
What reduces either one the most?
The setpoint, by roughly 3–5% of cooling energy per degree, and a ceiling fan, which lets most people accept a setpoint several degrees higher for the same comfort at a fraction of the draw.
Does my state change the answer?
It changes the size of the gap, never its direction. The same pair costs $93 a year apart in Hawaii and $23 in Nevada. Whichever uses less electricity uses less everywhere; only what that is worth moves.

Source: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A, June 2026. U.S. Government work, public domain.

How every figure on this page is computed · Where the data comes from