How Much Electricity Does an Air Conditioner Use? (Cost Per Hour, Day and Month)
Free calculator, browser-only. Sources verified on 2026-09-19. Last updated: 2026-09-19. Written by Y.W. Fung
An air conditioner uses 450-2,000W depending on BTU size. A 12,000 BTU unit costs about $0.19 an hour and $46 a month at 8 hours a day. Switching to an inverter model and raising the thermostat to 78°F cuts that by 20-40%, saving roughly $10-$20 a month.
At a glance
- What it is: window, portable or split cooling rated 5,000-18,000 BTU.
- How much it saves: $10-$20 a month from inverter operation plus thermostat setback.
- Payback time: 2-4 cooling seasons on the inverter premium; immediate for thermostat changes.
Air conditioning turns a modest summer electric bill into the biggest line item on the statement almost overnight, and the reason is simple: a compressor is one of the most power-hungry motors in an ordinary home. How much it actually costs depends on the unit's size in BTUs, whether it runs at a fixed speed or with an inverter compressor, and how many hours a day the thermostat calls for cooling. This guide breaks the cost down by wattage, by hour, day and month, and shows where an inverter model earns back its higher price tag.
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How many watts does an air conditioner use?
Air conditioners are rated in BTU (British Thermal Units) of cooling capacity, but the number that determines your bill is the electrical wattage the compressor draws to deliver that cooling. A small 5,000 BTU window unit typically pulls 450-550W, an 8,000 BTU unit around 700-800W, a 12,000 BTU unit near 1,100-1,300W, and an 18,000 BTU unit can draw 1,700-2,000W. Central systems sized in tons rather than BTU (1 ton equals 12,000 BTU) run considerably higher, with a 3-ton central AC drawing 3,000-4,000W including the indoor blower. Bigger is not automatically worse per BTU delivered, but an oversized unit for the room wastes energy cycling on and off rapidly, so matching capacity to room size matters as much as the wattage label.
How much does an AC cost per hour, day and month?
Once you know the wattage, the arithmetic is the same for every appliance: divide watts by 1,000 for kilowatts, multiply by hours run, then multiply by your electricity rate. An 8,000 BTU window unit running 8 hours a day at the US average of $0.16/kWh costs about 700W × 8h × $0.16 = $0.90 a day, or roughly $27 a month. Run the same unit 24 hours a day through a heat wave and the monthly cost jumps past $80. Central air, drawing 3,500W and cycling roughly 40-50% of the time on a hot day, typically adds $150-$250 a month to a US summer bill. You can enter your own rate and unit wattage into the calculator on the home page to get a number matched to your actual bill rather than a national average.
- 5,000 BTU window unit (~500W): about $0.08/hour, $19/month at 8 h/day
- 8,000 BTU window unit (~750W): about $0.12/hour, $29/month
- 12,000 BTU unit (~1,200W): about $0.19/hour, $46/month
- 18,000 BTU unit (~1,850W): about $0.30/hour, $71/month
- 3-ton central AC (~3,500W, 45% duty cycle): about $150-$250/month in peak summer
Is an inverter air conditioner worth it?
A fixed-speed (non-inverter) air conditioner runs its compressor at full power until the room hits the target temperature, then switches off completely, and repeats that cycle all day. An inverter unit instead varies compressor speed continuously, ramping down to a fraction of full power once the room is close to temperature rather than switching off and restarting. Because restarting a compressor is one of the most electrically demanding moments in its cycle, inverter units typically use 20-40% less electricity than a fixed-speed unit of the same cooling capacity over a full day, and they hold room temperature far more steadily. The trade-off is upfront price: inverter window and split units usually cost 25-50% more to buy, so the payback period is generally two to four cooling seasons in a hot climate and longer in a mild one.
What do SEER and EER ratings mean?
US central and split systems carry a SEER (Seasonal Energy Efficiency Ratio) rating, and window units carry an EER (Energy Efficiency Ratio); both describe cooling output divided by electricity input, so a higher number means less electricity for the same cooling. Federal minimums have risen to SEER 14-15 in most US states, but older systems installed a decade or more ago may sit at SEER 10-13, using roughly 20-30% more electricity than a new minimum-efficiency system for identical cooling. Upgrading a genuinely old central AC to a modern SEER 16-18 unit commonly cuts the cooling portion of a summer bill by a fifth to a third, though the upfront cost of replacement is substantial and should be weighed against remaining equipment life.
How can you lower AC running costs?
- Set the thermostat to 78°F (25-26°C) rather than 72°F; each degree lower adds roughly 3-5% to cooling energy use
- Use a programmable or smart thermostat to let the house warm slightly while nobody is home
- Close blinds and curtains on sun-facing windows during the hottest hours to cut heat gain before it reaches the AC
- Replace or clean the air filter monthly in cooling season; a clogged filter forces the compressor to work harder for the same cooling
- Size any replacement unit correctly for the room or house; an oversized unit cycles inefficiently and cools unevenly
Air conditioner running cost by size and electricity rate (8 hours/day, 30 days)
| Unit | Watts | Per hour @ $0.16 | Per month (US) | Per month @ 26p (UK) |
|---|---|---|---|---|
| 5,000 BTU window unit | 500W | $0.08 | $19 | £31 |
| 8,000 BTU window unit | 750W | $0.12 | $29 | £47 |
| 12,000 BTU unit | 1,200W | $0.19 | $46 | £75 |
| 18,000 BTU unit | 1,850W | $0.30 | $71 | £115 |
| 3-ton central AC (45% duty) | ~1,575W avg | $0.25 | $180* | £293* |
How much can you save, and how fast?
| Device / change | Cost | Yearly saving | Payback |
|---|---|---|---|
| Raise thermostat 72°F to 78°F | $0 | $90-$160 | Immediate |
| Inverter unit instead of fixed speed | +$150 upfront | $60-$110 | 2-3 seasons |
| Clean or replace the filter monthly | $30/year | $25-$50 | Under 1 season |
| Blackout blinds on sun-facing windows | $80 | $40-$80 | 1-2 seasons |
Cost vs savings summary
- Typical spend: $0-$150.
- Typical saving: $150-$300 a cooling season.
- Net: positive within the first summer.
Frequently asked questions
How much electricity does an AC use per day?
- A typical 8,000 BTU window unit run 8 hours a day uses about 6 kWh, roughly $0.96 at $0.16/kWh. Central air run through a hot day can use 25-40 kWh, costing $4-$6.50 a day at the US average rate.
Does an inverter AC really save money?
- Yes, typically 20-40% less electricity than a fixed-speed unit of the same capacity, because it avoids repeated full-power compressor restarts. On a $46 monthly cooling bill that can mean $10-$18 saved per month in peak season.
Is it cheaper to leave the AC on all day or turn it off and on?
- For most homes, letting the temperature drift up a few degrees while you are out and cooling down again when you return uses less total energy than holding one constant low temperature all day, especially with a fixed-speed unit.
How many watts does a 12,000 BTU air conditioner use?
- Most 12,000 BTU (1-ton) units draw about 1,100-1,300 watts. At $0.16/kWh that is roughly $0.19 per hour of continuous running, or about $46 a month at 8 hours a day.
Does a bigger AC unit cost more to run?
- A higher-BTU unit draws more watts, but an undersized unit for the space runs almost continuously, which can cost more overall than a correctly sized larger unit that cycles off once the room reaches temperature.
Key takeaways
- Wattage, not BTU alone, determines your electricity cost; check the unit's watt rating on the nameplate
- A window unit typically costs $0.08-$0.30 per hour depending on size; central AC costs $150-$250 a month in peak summer
- Inverter compressors use 20-40% less electricity than fixed-speed units of the same capacity
- Every degree above 72°F on the thermostat saves roughly 3-5% on cooling costs
- Enter your unit's wattage and local rate into the calculator on the home page for an exact monthly figure
Methodology & data sources
Every cost figure here is calculated with kWh = (watts × hours per day) ÷ 1000, multiplied by a regional average electricity price: about $0.16/kWh (US), 26p/kWh (UK), NT$3.5/kWh (Taiwan), HK$1.5/kWh (Hong Kong) and ¥31/kWh (Japan). Appliance wattages are taken from manufacturer nameplate ratings and published energy-label ranges for current models. Real bills vary with climate, insulation, appliance age and tiered or time-of-use tariffs, so we recommend re-running the numbers with the unit rate printed on your own latest bill.
Sources verified on 2026-09-19 - EIA, Ofgem, Energy Star, DOE, CLP Power, Taipower, METI
Last updated: 2026-09-19
Run the numbers for your own home
Enter your local rate, standing charge and appliance hours in the free electricity cost calculator to see your own monthly estimate.
Open the calculatorFAQ - Air Conditioner Cost
How much does a 1200W air conditioner cost per hour?
- At $0.16/kWh, 1.2 kW × $0.16 = $0.19 per hour.
How much does it cost to run for 8 hours a day?
- $0.19 × 8 hours = $1.54 per day, or $46.08 per month over 30 days.
Does a 1200W air conditioner use a lot of electricity?
- At 8 hours per day, it uses 9.6 kWh daily and 288 kWh monthly. Whether that is a lot depends on usage time and appliance efficiency, so compare the estimate with a plug-in meter or your utility data.
How much does this air conditioner cost to run for a year?
- At 8 hours per day and $0.16/kWh, the estimated yearly electricity cost is $560.64 for 365 days. Actual cost changes with the measured wattage, operating time, and local electricity rate.
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