How Many Watts Does an Air Conditioner Use? Window, Portable, Mini-Split and Central AC

Window AC Watts by BTU: 5,000 to 24,000

A window air conditioner’s running watts are its cooling capacity in BTU per hour divided by its efficiency rating. The table uses two published efficiency figures for each size. The first is the federal minimum CEER that applied from 2014 until May 26, 2026, which is close to what an older or basic conventional unit draws whenever its compressor runs [1]. The second is the median CEER of ENERGY STAR-certified window units in that size band. Every one of the 608 models on ENERGY STAR’s room AC list on November 12, 2026, including 540 window units, had a variable-speed (inverter) compressor [4], and for those units BTU ÷ CEER is a season average, not the peak.

Running watts = BTU ÷ CEER (our arithmetic). Minimum CEER from 10 CFR 430.32(b) for units with louvered sides and no heat [1]; ENERGY STAR medians are our arithmetic on the certified-model list, cooling-only window units [4]. The starting range is 2–3× running, the multiplier Generac gives for motor loads [14]; it is a planning range, not a measured figure for any unit. The annual column multiplies by 750 hours, the cooling season DOE’s test procedure assumes [3].

Why an inverter unit’s label watts are higher than the average

DOE tests variable-speed room ACs at four outdoor temperatures from 95 °F down to 82 °F and weights the results toward the milder conditions [3], so CEER reflects a typical day. On the hottest afternoon the compressor runs flat out. Frigidaire’s 24,000 BTU FHWW245WE2 shows the gap: its CEER of 13.3 works out to about 1,805 W on average, but the spec sheet lists 2,630 W [6][4]. For sizing a battery or a circuit, use the watts or amps on the label. Use the CEER figure only to estimate energy over a season.

The 2026 efficiency rules

Room ACs made or imported on or after May 26, 2026 must meet higher minimums: CEER 13.1 under 6,000 BTU, 13.7 at 6,000–7,900, and 16.0 from 8,000 to 19,900 BTU, up from 10.7–11.0 before [2][1]. Older stock can still be sold, and the units already in windows aren’t affected, so the conventional column above is still the right planning number for most existing ACs.

Real Models: Nameplate Watts vs the Math

Five current or recent models with published electrical specs. In each case the label figure is the one to size a power station or circuit around; the check column shows how it compares with the efficiency math.

Published watts are the manufacturer’s or a retailer’s spec listing as cited. The Midea Duo’s listings disagree on its ASHRAE rating (10,000 vs 12,000 BTU), so we don’t compute an efficiency for it. The MRCOOL figure is our arithmetic from its certified EER2, because the listings we found give the rating and circuit size but not the input watts. The Frigidaire FHPC102AB1 has been discontinued; it is shown as a typical single-hose portable.

Mini-Split and Central AC Watts

Mini-splits are the most efficient way to cool one room. MRCOOL’s 12,000 BTU DIY 5th Gen unit is certified at EER2 12.5 and SEER2 23.5 with a continuously variable compressor [11][12]: about 960 W at the 95 °F rating point and about 510 W averaged over a season (12,000 ÷ 23.5, our arithmetic). That is roughly half the average draw of a 12,000 BTU conventional window unit.

Central air is sized in tons; one ton is 12,000 BTU per hour. Since January 1, 2023, new split-system central ACs must reach SEER2 13.4 in the North and 14.3 in the Southeast and Southwest (13.8 at 45,000 BTU and up), and the Southwest also sets an EER2 floor of 11.7 for most systems under 45,000 BTU (11.2 above that) [1][13]. The table divides by that EER2 floor for the hot-afternoon draw and by the national SEER2 minimum for the season average:

Our arithmetic on the federal minimums; more efficient systems draw less. Generac puts a 3-ton system at about 3.5–5 kW running and up to 15–18 kW at start-up [14], higher than the floor-based figures; use your own system’s nameplate or EER2 rating where you can. The kWh range runs from hot-afternoon to season-average draw.

kWh Per Day and Per Month

Energy depends on how many hours the compressor actually runs, not how long the AC is switched on. A conventional unit cycles off once the room reaches the set temperature; an inverter unit slows down instead. The table shows a conventional 10,000 BTU window unit (about 915 W at the pre-2026 minimum CEER) and an ENERGY STAR inverter unit of the same size at its season average (about 665 W).

Month = 30 days. Our arithmetic. For a whole season, DOE’s test procedure assumes 750 hours of cooling a year [3], which is how ENERGY STAR’s annual kWh figures are calculated; we checked that all 608 listed models match BTU ÷ CEER × 750 hours [4].

For scale: the average U.S. home uses about 28 kWh a day in total, and air conditioning is its largest single electricity use. Our household electricity guide breaks that down by state and month from EIA data. A 3-ton central system running 8 hours uses about 21–25 kWh, which is most of that daily average on its own.

Verdict: Size for the Label, Plan for the Start

Most window ACs draw about 350–1,100 W running, portables about 1,000–1,200 W, and a 12,000 BTU mini-split under 1,000 W. Read the watts or amps on your unit’s label, then check whether it has an inverter: that decides whether the start needs about 1.5× or about 3× the running watts. For any 120 V window or portable unit up to 12,000 BTU, the Bluetti Elite 200 V2 (our score 91/100) clears both checks. Currently $898.99 on Amazon, it runs an 8,000 BTU unit for close to three hours with the compressor flat out. For 240 V units, a mini-split on a transfer switch, or more hours per charge, step up to the EcoFlow Delta Pro 3 (95/100).