ManualHarbor

How Much Electricity Does an Air Conditioner Use?

Updated October 9, 2026

How much electricity an air conditioner uses depends on two numbers: its cooling capacity (Btu per hour) and its efficiency rating. Here are two examples worked from federal efficiency floors. An 8,000 Btu/h window unit at today's federal minimum (CEER 16.0) draws about 500 watts while cooling, roughly 9 cents an hour at the U.S. average residential price of 18.19¢/kWh. A 3-ton central system rated at 11.7 EER2 draws about 3.1 kW at the 95°F test condition, roughly 56 cents an hour. Over a full year, EIA's 2020 household survey found that homes using air conditioning averaged 2,318 kWh for it, which is about $422 at today's average rate.

Capacity is not power: the formula that converts one to the other

Air conditioner sizes are given in Btu per hour (Btu/h) or tons. One ton equals 12,000 Btu/h. These numbers tell you how much heat the unit can remove from your home. They do not tell you how much electricity it uses. Electrical input is measured in watts (W) or kilowatts (kW), and the efficiency rating is what links the two.

  • Input power (kW) = cooling capacity (Btu/h) ÷ EER (Btu per watt-hour) ÷ 1,000
  • Energy (kWh) = input power (kW) × hours the compressor runs
  • Cost = kWh × your electricity price ($/kWh)

The units work out because an EER is Btu per watt-hour. Dividing Btu/h by Btu/Wh leaves watts. A common mistake is to treat a 12,000 Btu/h unit as if it draws 12,000 watts. In reality it draws only a fraction of that, because air conditioners move heat rather than create it.

How to read EER2, CEER and SEER2

  • EER / EER2 — Where you'll see it: Central AC, heat pumps, mini-splits; What it measures: Cooling output (Btu/h) ÷ electrical input (W) at a 95°F outdoor test condition, so it reflects hard-working, hot-day efficiency; Best use: Estimating watts while the unit runs at full output
  • CEER — Where you'll see it: Room (window and through-the-wall) ACs; What it measures: Btu per Wh from DOE's room AC test, which combines cooling-mode power over 750 hours a year with standby and off-mode power for the rest of the year; Best use: Estimating running watts (slightly conservatively) and annual kWh
  • SEER / SEER2 — Where you'll see it: Central AC, heat pumps, mini-splits; What it measures: Total heat removed over a cooling season ÷ total electricity used that season, in Btu/Wh; Best use: Estimating seasonal kWh

Definitions: DOE's 2023 central AC standards FAQ (EER, SEER), the ENERGY STAR heat pump specification (EER2, SEER2), and DOE's room AC test procedure in 10 CFR 430 (CEER).

Some points to keep in mind:

  • SEER2 and EER2 replaced SEER and EER in 2023. DOE changed the test procedure to better reflect real installations. The new numbers look similar to the old ones, but DOE says they are not directly comparable.
  • A high SEER2 doesn't guarantee a high EER2. In the Southwest, DOE requires split ACs under 45,000 Btu/h to meet 11.7 EER2 if they're below 15.2 SEER2. Units rated at or above 15.2 SEER2 only need 9.8 EER2. If you care about peak summer demand, look at both numbers.
  • CEER includes standby power. That slightly lowers the rating, so capacity ÷ CEER gives a conservative (slightly high) estimate of running watts. The DOE test assumes 750 hours of cooling a year. ENERGY STAR's annual kWh figure for room ACs follows the same math: capacity × 0.75 ÷ CEER. All 570 room AC listings in ENERGY STAR's dataset on October 10, 2026, matched that formula within rounding. Our room air conditioner guides show CEER and annual kWh for each certified model.

Worked examples: per hour, per day and per month

Assumptions: an electricity price of 18.19¢/kWh (EIA, January–July 2026 average); 8 hours of operation per day, the same daily assumption the FTC requires on room AC EnergyGuide labels; and a 30-day month. These figures treat the unit as running at rated output for those hours. Real units cycle on and off or slow down, so treat the numbers as an upper estimate for those hours.

  • 8,000 Btu/h window AC, older — Rating used and where it comes from: CEER 10.9, the federal minimum for this class from June 2014 to May 2026; Power while running: 734 W; Per hour: $0.13; Per 8-hour day: $1.07; Per 30-day month: $32.04
  • 8,000 Btu/h window AC, new — Rating used and where it comes from: CEER 16.0, the federal minimum for this class made from May 26, 2026; Power while running: 500 W; Per hour: $0.09; Per 8-hour day: $0.73; Per 30-day month: $21.83
  • 12,000 Btu/h ductless mini-split — Rating used and where it comes from: EER2 13.0, the median of 12,000 Btu/h ENERGY STAR mini/multi-split listings; Power while running: 923 W; Per hour: $0.17; Per 8-hour day: $1.34; Per 30-day month: $40.30
  • 36,000 Btu/h (3-ton) central AC — Rating used and where it comes from: EER2 11.7, DOE's Southwest minimum for split ACs under 15.2 SEER2; Power while running: 3,077 W; Per hour: $0.56; Per 8-hour day: $4.48; Per 30-day month: $134.33

Example (new window unit, step by step): 8,000 Btu/h ÷ 16.0 Btu/Wh = 500 W, or 0.5 kW. Then 0.5 kW × 8 hours = 4 kWh a day. At $0.1819 per kWh, that's $0.73 a day and $21.83 for 30 days.

The central AC row uses EER2, which is measured at 95°F. On milder days the system draws less power. In a heat wave it may run far more than 8 hours. For ductless systems, see the certified models in our mini-split heat pump listings. They are rated with the same EER2 and SEER2 metrics.

Seasonal estimate with SEER2

For a whole cooling season, use the seasonal rating together with an estimate of equivalent full-load hours. That is the number of hours the unit would need to run at full capacity to deliver the season's cooling. State energy-efficiency Technical Reference Manuals (TRMs) publish these hours by location.

Seasonal kWh = capacity (Btu/h) × full-load cooling hours ÷ SEER2 ÷ 1,000

Example: a 36,000 Btu/h (3-ton) central AC at 18.19¢/kWh.

  • Chicago, IL (Illinois TRM, single-family) — Full-load cooling hours: 570; At SEER2 13.4: 1,531 kWh, about $279; At SEER2 15.2: 1,350 kWh, about $246
  • Belleville, IL (Illinois TRM, single-family) — Full-load cooling hours: 1,035; At SEER2 13.4: 2,781 kWh, about $506; At SEER2 15.2: 2,451 kWh, about $446
  • Texas "South" climate zone (Texas TRM, from the ENERGY STAR central AC calculator) — Full-load cooling hours: 2,209; At SEER2 13.4: 5,935 kWh, about $1,080; At SEER2 15.2: 5,232 kWh, about $952

Calculations by ManualHarbor. Hours come from the 2019 Illinois TRM v7.0 (derived from program evaluation data) and the 2015 Texas TRM v2.1. Both manuals were written for SEER-rated equipment.

Why these two ratings? 13.4 SEER2 is the federal minimum for split-system central ACs in the North. 15.2 SEER2 is ENERGY STAR's minimum for heat pumps. ENERGY STAR's central air conditioner program was retired effective February 1, 2026. Because kWh scale with 1 ÷ SEER2, going from 13.4 to 15.2 cuts seasonal use by about 12% (1 − 13.4 ÷ 15.2 = 11.8%).

For a room AC, DOE's 750-hour basis gives a quick annual figure: capacity × 0.75 ÷ CEER. An 8,000 Btu/h unit at CEER 16.0 comes to 375 kWh (about $68 a year), and at CEER 10.9 it comes to 550 kWh (about $100).

What real homes use: EIA's household survey

Engineering formulas are useful for comparing equipment. EIA's Residential Energy Consumption Survey (RECS) shows what households actually used. In 2020, air conditioning was the largest single use of electricity in U.S. homes, at about 19% of residential consumption.

  • All U.S. homes using AC — Average AC electricity per home using AC, 2020: 2,318 kWh; At today's 18.19¢/kWh: about $422
  • Very cold and cold — Average AC electricity per home using AC, 2020: 1,310 kWh; At today's 18.19¢/kWh: about $238
  • Mixed-humid — Average AC electricity per home using AC, 2020: 2,293 kWh; At today's 18.19¢/kWh: about $417
  • Mixed-dry and hot-dry — Average AC electricity per home using AC, 2020: 2,691 kWh; At today's 18.19¢/kWh: about $489
  • Hot-humid — Average AC electricity per home using AC, 2020: 4,173 kWh; At today's 18.19¢/kWh: about $759
  • Marine — Average AC electricity per home using AC, 2020: 902 kWh; At today's 18.19¢/kWh: about $164

Source: EIA RECS 2020, Table CE5.3a. Dollar column calculated by ManualHarbor.

EIA reports the indoor blower ("air handlers for cooling") separately. That added an average of 457 kWh for homes that have one, and 720 kWh in hot-humid climates.

What drives air conditioner electricity use

Climate and run time

Run time explains most of the spread in the tables above. The same 3-ton system uses almost four times as much electricity with Texas "South" hours as with Chicago hours.

Thermostat setpoint

DOE's Energy Saver Guide recommends setting the thermostat as high as is comfortable while you're home and raising it when you're asleep or away. It estimates that adjusting the setting by 7–10°F for 8 hours a day can save up to 10% a year on heating and cooling. A 2012 DOE article estimated that cooling to 78°F instead of 72°F saves 6–18% on the cooling bill. DOE also notes that a ceiling fan lets you raise the thermostat about 4°F with no loss of comfort, as long as you turn the fan off when you leave the room. A schedule on a smart thermostat makes the setback automatic.

Insulation, windows and ducts

According to DOE, new efficient equipment alone can cut energy use by 20% or more. Pairing it with insulation, air sealing and better thermostat settings can cut heating and cooling bills by about 30%. DOE says leaky ducts in an attic or crawl space can add hundreds of dollars a year. The DOE-funded Building America Solution Center puts duct losses at more than 30% of heating and cooling energy when ducts run through unconditioned space. Windows matter too: DOE attributes 25–30% of residential heating and cooling energy use to heat gain and loss through windows. Keeping shades closed on sunny days helps.

Sizing

DOE warns that an oversized air conditioner is less efficient and less effective than a properly sized one. The Building America Solution Center adds that oversizing causes short cycling, which wastes energy and controls humidity poorly. Ask your contractor for an ACCA Manual J load calculation.

Age and maintenance

DOE suggests considering replacement when a central AC or heat pump is more than 10 years old. It also recommends cleaning or replacing filters monthly or as the manufacturer recommends. Leave refrigerant and electrical work to a licensed HVAC technician. An AC's capacitors can hold a dangerous charge even when the power is off.

Your electricity price

In July 2026, EIA's state averages ranged from 12.72¢/kWh in Louisiana to 48.00¢/kWh in Hawaii. At those two prices, the same 2,318 kWh would cost about $295 or about $1,113. Use the price per kWh from your own bill.

To check your own usage, use your utility's hourly or daily smart-meter data to compare hot days with mild ones. Don't open a disconnect box or electrical panel to take measurements. Leave that to a licensed electrician or HVAC technician.

FAQ

How much does it cost to run an air conditioner for 24 hours?

Multiply the running kW by 24 hours and by your price. At 18.19¢/kWh, an 8,000 Btu/h window unit drawing 0.5 kW would cost at most about $2.18 a day. A 3-ton central AC drawing 3.08 kW would use about 73.8 kWh, or about $13.43. Most units cycle off or slow down for part of the day, so real costs are usually lower except during extreme heat.

Is a window unit cheaper to run than central air?

Per hour, yes, because it's much smaller. If you only need one or two rooms cooled, small units running in just those rooms will typically use fewer kWh than cooling the whole house. If you need the whole house cool, compare ratings and run time instead. CEER and SEER2 come from different tests, so don't compare them directly.

Does a higher SEER2 rating lower my bill?

Yes, in proportion. Seasonal kWh equals capacity × hours ÷ SEER2, so moving from 13.4 to 15.2 SEER2 cuts cooling electricity by about 12%. That holds for the same house, hours and thermostat setting.

Should I turn the AC off or up when I leave?

DOE recommends raising the temperature when you're away or asleep rather than holding a low setting all day. If you have a heat pump, check the heat pump guides and your manufacturer's instructions. DOE cautions that heating-season setbacks on heat pumps can trigger costly backup heat.

Related guides

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