How Much Electricity Does an Air Conditioner Use? (Per hour, day, and month)

A typical 1.5HP (12,000 BTU) air conditioner uses about 0.5 to 1 kWh of electricity per hour on a hot day, even though it draws about 1.2 kilowatts while the compressor runs. The common sizes compare like this:

Size (retail label)	Cooling capacity	Draw while running	Typical average use per hour
1HP	about 9,000 BTU/h	0.9 kW	0.36 to 0.72 kWh
1.5HP	12,000 BTU/h	1.2 kW	0.48 to 0.96 kWh
2HP	about 18,000 BTU/h	1.8 kW	0.72 to 1.44 kWh

Estimates for fixed-speed units at an efficiency of about EER 10, with the compressor running 40% to 80% of the time.

The number printed on the unit is its running draw, while your bill reflects how often the compressor actually runs. Every figure here is in kilowatt-hours (kWh), the unit your meter and bill use.

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Air Conditioner Power: Watts, KW and kWh

Air conditioner power is the rate at which the unit draws electricity while it runs, shown in watts (W) or kilowatts (kW) on the label. 

Energy use is that power multiplied by time, measured in kilowatt-hours (kWh), which is what your meter counts and your utility charges for.

Reading the power rating on your AC label

The rating sticker sits on the side of the indoor unit of a split system, or on the back or side panel of a window or portable unit. Three entries matter.

Rated power input (W) is the electricity the unit draws when it runs at full capacity under test conditions. Use this number for every calculation on this page.

Rated cooling capacity (BTU/h or kW) is how much heat the unit removes per hour. It tells you which room size the unit suits, not how much power it consumes.

EER (energy efficiency ratio) is cooling capacity in BTU/h divided by power input in watts. A higher EER means less power for the same cooling. A 12,000 BTU/h unit with an EER of 10 draws about 1,200 W.

Why “watts per hour” is the wrong unit

Watt (W) is a rate: one joule of energy per second. Because a watt already includes time, “watts per hour” mixes up two different quantities.

Several HVAC technicians still describe central air conditioning as using “2,000 and 3,500 watts per hour.” Read that as 2 to 3.5 kW.

Kilowatt-hour (kWh) is the energy used by drawing 1,000 watts for one hour. A 1,200 W air conditioner running for one hour uses 1.2 kWh.

Unit is the term many prepaid meters and bills use in countries such as Nigeria, India, and Pakistan. One unit is one kWh.

HP, BTU and Tons: Converting Between Them

HP on a retail label is a size class, not an electrical measurement. The table shows the usual mapping, with running draw estimated from the BTU ÷ EER formula.

Retail size	Cooling capacity (BTU/h)	Cooling tons	Cooling output (kW)	Typical running draw (kW)
1HP	9,000	0.75	2.6	0.8 to 1.0
1.5HP	12,000	1.0	3.5	1.0 to 1.4
2HP	18,000	1.5	5.3	1.6 to 2.0

One ton of cooling equals 12,000 BTU/h. Brands map HP to BTU differently, so trust the BTU figure over the HP badge.

Watch the “1.5 ton” label in particular: in markets such as India, it means 18,000 BTU/h, which is the 2HP row above, not 1.5HP. 

Take, for example, Onida, an Indian manufacturer, which puts 1.5-ton models at 1.05 to 1.8 kWh per hour depending on star rating, which fits that row.

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How Much Electricity Does an AC Use Per Hour?

A fixed-speed 1.5HP air conditioner draws about 1.2 kW while running and averages about 0.7 kWh per hour on a hot day, and that average is the figure that drives your bill. 

Smaller units draw less and larger units more, roughly in proportion to cooling capacity.

1HP Aircon Power Consumption Per Hour

A 1HP unit draws 0.8 to 1.0 kW while the compressor runs. The hourly average falls near 0.35 kWh in a mild room and climbs toward 0.7 in extreme heat.

Measure	Typical value
Cooling capacity	about 9,000 BTU/h
Draw while running	0.9 kW
Average per hour, hot day	0.54 kWh

1.5HP Air Conditioner Power Consumption Per Hour

A 1.5HP unit draws 1.0 to 1.4 kW while running and averages about 0.72 kWh over a hot hour.

Measure	Typical value
Cooling capacity	12,000 BTU/h
Draw while running	1.2 kW
Average per hour, hot day	0.72 kWh

12,000 BTU AC Power Consumption Per Hour

Two 12,000 BTU units can draw very different power because efficiency varies. The running draw equals 12,000 divided by the EER.

EER	Draw while running	Average per hour, hot day
8	1.50 kW	0.90 kWh
10	1.20 kW	0.72 kWh
12	1.00 kW	0.60 kWh
14	0.86 kW	0.51 kWh

Split, Window and Portable AC Compared

The figures below are estimates, but they give you an idea of how each AC type consumes or uses power:

Type	Published running draw
Window	900 to 1,440 W
Split (ductless)	Close to a window unit of the same capacity, usually lower because EER is higher
Portable	About 880 W, or 2,900 to 4,100 W
Central	2,000 to 3,500 W

Portable units are generally less efficient than split units of the same capacity, which is part of why their published draw runs high. 

Figure	Likely reason	What to use
5,000 BTU unit at 0.25 to 0.4 kWh per hour  or 0.5 kWh	One figure may reflect average use with cycling, the other full running draw	Running draw for sizing a generator, average for estimating a bill
Portable AC at about 880 W versus 2,900 to 4,100 W	Different capacity classes and designs	The rated input on your own label
“Watts per hour”	A unit error	Read it as kW
360 kWh a month for a 5,000 BTU unit	The arithmetic works out to 0.5 kWh for all 720 hours in a month, which assumes nonstop running	Multiply by your real hours and duty cycle

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How to Calculate Your AC’s Electricity Usage

Multiply the unit’s running power in kilowatts by the hours it is on and by the share of that time its compressor actually runs. The result is energy in kWh, which you can then multiply by your electricity rate.

The formula with a worked example

1. Find the rated power input on the label, for example, 1,200 W.
2. Divide by 1,000 to get kilowatts: 1.2 kW.
3. Multiply by the hours the AC is on. For 8 hours, 1.2 kW × 8 h = 9.6 kWh at full power.
4. Multiply by the duty cycle, the share of time the compressor runs. At 60%, 9.6 × 0.6 = 5.76 kWh.
5. Multiply by your rate per kWh to get the cost.

Real use in this example is 40% lower than the label-only figure of 9.6 kWh. For a version that does the arithmetic for you, use our custom FREE AC power and electricity consumption calculator.

Why Real Usage is Lower than the Label: Duty Cycle

A fixed-speed compressor switches off when the room reaches the set temperature and back on when it warms. 

For example, a properly sized single-stage unit runs in 15- to 20-minute cycles, one or two an hour and sometimes three, depending on the heat. 

That cycle pattern translates directly into duty cycle. One 15-minute cycle an hour is a duty cycle of 25%. 

Two 17.5-minute cycles are about 58%. Three 20-minute cycles mean the compressor never stops, a 100% duty cycle. 

The runtime chart for central units shows run time climbing as the outdoor temperature rises above the design temperature, reaching continuous operation at 15°F above it.

The table below uses three illustrative bands: mild (40%), hot (60%), and extreme heat (80%). These are assumptions for planning, not measured data, so replace them with your own results using the method below.

Unit	Draw while running	Mild day (40%)	Hot day (60%)	Extreme heat (80%)
1HP	0.9 kW	0.36 kWh/h	0.54 kWh/h	0.72 kWh/h
1.5HP / 12,000 BTU	1.2 kW	0.48 kWh/h	0.72 kWh/h	0.96 kWh/h
2HP	1.8 kW	0.72 kWh/h	1.08 kWh/h	1.44 kWh/h

Average kWh per hour = running kW × duty cycle. Inverter units slow down instead of switching off, so use their average power as a share of running power.

Measure your own AC in 24 hours

1. Choose a method. A plug-in energy meter works for window and portable units. A hardwired split unit needs a sub-meter, a clamp meter, or a main-meter reading with other heavy loads off.
2. Record the meter reading at a fixed time, such as 8 p.m., plus the thermostat setting.
3. Run the AC as you normally would for 24 hours and note how many hours it was on.
4. Record the reading again at the same time the next day.
5. Subtract the first reading from the second. If you used the main meter, run the same 24 hours with the AC off on another day and subtract that baseline.
6. Divide the AC’s kWh by the hours it was on to get your actual average kWh per hour. Then divide that by the running kW on the label to get your duty cycle, and compare it to the table above.

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How Much Electricity Does an AC use per day (24 hours)?

A 1.5HP air conditioner used for 8 hours a day uses about 5.8 kWh on a typical hot day. 

Depending on how hard the compressor works, that ranges from 3.8 to 7.7 kWh, and running it for all 24 hours takes about 17 kWh at the hot-day average.

How much electricity does a 12,000 BTU AC use per day?

A 12,000 BTU unit draws about 1.2 kW while running, so its daily use follows from the hours and the duty cycle.

Hours on	Mild day (40%)	Hot day (60%)	Extreme heat (80%)
8 hours	3.8 kWh	5.8 kWh	7.7 kWh
12 hours	5.8 kWh	8.6 kWh	11.5 kWh

Daily kWh by hours of use (4, 8, 12, 24 hours)

The table assumes a hot day, with the compressor running 60% of the time.

Hours on	1HP	1.5HP	2HP
4 hours	2.2 kWh	2.9 kWh	4.3 kWh
8 hours	4.3 kWh	5.8 kWh	8.6 kWh
12 hours	6.5 kWh	8.6 kWh	13.0 kWh
24 hours	13.0 kWh	17.3 kWh	25.9 kWh

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How Much Electricity Does an AC use Per Month, and what does it cost?

A 1.5HP air conditioner used 8 hours a day uses about 173 kWh a month at the hot-day average, and about 518 kWh if it runs around the clock for 30 days. 

Cost is that figure multiplied by your rate per kWh.

Monthly kWh by hours of daily use

The table assumes 30 days and a 60% duty cycle.

Hours on per day	1HP	1.5HP	2HP
4 hours	65 kWh	86 kWh	130 kWh
8 hours	130 kWh	173 kWh	259 kWh
12 hours	194 kWh	259 kWh	389 kWh
24 hours	389 kWh	518 kWh	778 kWh

How much does 30 minutes of AC cost?

Half an hour of AC costs running kW × 0.5 × your rate if the compressor never stops, which is the upper estimate. With normal cycling, the figure is lower.

Unit	Full-power 30 minutes	Hot-day average, 30 minutes
1HP	0.45 kWh	0.27 kWh
1.5HP	0.60 kWh	0.36 kWh
2HP	0.90 kWh	0.54 kWh

Taking Nigeria as an example, for a 1.5HP unit at ₦225 per kWh, half an hour costs about ₦135 at full power and about ₦81 at the hot-day average. 

At ₦63 per kWh, the same half hour costs about ₦38 and ₦23. To price your own unit at your own tariff, use the AC running cost calculator.

What an AC costs at different electricity rates

The same 1.5HP unit costs very different amounts depending on where it runs. The table applies the hot-day average of 0.72 kWh per hour. 

The $0.10, $0.20, and $0.30 rows are example rates, not national averages.

Rate per kWh	30 minutes	1 hour	8 hours	Month (8 h/day)
$0.10	$0.04	$0.07	$0.58	$17.28
$0.20	$0.07	$0.14	$1.15	$34.56
$0.30	$0.11	$0.22	$1.73	$51.84
₦63 (Nigeria, Band B)	₦23	₦45	₦363	₦10,886
₦225 (Nigeria, Band A)	₦81	₦162	₦1,296	₦38,880
Diesel generator, ₦250 to ₦400	₦90 to ₦144	₦180 to ₦288	₦1,440 to ₦2,304	₦43,200 to ₦69,120
Petrol generator, ₦400 to ₦700	₦144 to ₦252	₦288 to ₦504	₦2,304 to ₦4,032	₦69,120 to ₦120,960

Nigeria’s regulator, NERC, sets tariffs by band according to hours of daily supply. 

Band A is about ₦225 per kWh for feeders with 20 or more hours of supply, and ₦40 to ₦63 for Bands B to E. 

For example: Let’s also estimate generator electricity at ₦250 to ₦400 per kWh for diesel and ₦400 to ₦700 for petrol. 

You also need to know that electricity tariffs vary by distribution company and state, so check your latest bill.

Generator electricity in the table costs roughly 1.1 to 11 times as much per kWh as the grid rates above it.

To learn more about the various distribution companies in Nigeria and electricity bands, read this guide on: Understanding Nigeria’s Electricity Band and Rate.

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Which AC Consumes Less Electricity?

A high-efficiency inverter air conditioner, sized correctly for the room, uses the least electricity. 

Of two units with the same cooling capacity, the one with the higher EER draws less power, and the one that matches the room runs fewer wasted hours.

Inverter vs non-inverter AC

Feature	Inverter	Non-inverter (fixed speed)
Compressor	Slows down to hold the temperature	Runs at full speed, then switches off
Power pattern	Steady and lower once the room is cool	Full running draw each cycle, then zero
Startup surge	Gentler	Higher, commonly two to three times the running draw
Upfront price	Higher	Lower
Best fit	Many hours a day, hot climates, generator or solar power	A few hours a day on a tight budget

An inverter pays back faster the more hours you run it. For daily all-night use, it is usually the lower-cost choice over the unit’s life, while at two hours a day the savings may never cover the higher price. 

For a deeper comparison, see this guide to inverter vs non-inverter AC.

1HP vs 1.5HP vs 2HP: Matching Size to Room

A smaller unit uses less power per hour, but only if it can hold the room’s temperature. 

An oversized unit cycles on and off in under 10 minutes, and an undersized one runs continuously, so the right size is the smallest unit that cools your room on the hottest day.

Size	Draw while running	Average per hour, hot day	Suits
1HP	0.9 kW	0.54 kWh	Small bedroom or office, one or two people
1.5HP	1.2 kW	0.72 kWh	Standard bedroom or small living room
2HP	1.8 kW	1.08 kWh	Large living room, open plan, or a sun-exposed room

To check your room against a specific capacity, use our FREE custom BTU AC calculator.

Energy ratings and what to check on the label

• A higher EER cuts running draw directly: on a 12,000 BTU unit, moving from EER 10 to EER 12 lowers the draw from about 1,200 W to 1,000 W, a drop of roughly 17%.
• SEER and CEER ratings average efficiency over a season, so compare them only with other SEER or CEER figures, not with EER.
• In markets with star labels, such as India’s scheme, more stars mean lower consumption for the same capacity.

Which AC uses less in hot climates and on unreliable grids (Nigeria Example)

In a hot, humid climate with long daily run times, a correctly sized inverter unit with a high efficiency rating is the lowest-consuming option. 

The same unit costs more than three times as much to run on a Band A feeder as on Band B.

• At ₦225 per kWh, a 1.5HP unit used 8 hours a night costs about ₦1,296 per night, so a more efficient unit pays back faster there than on a cheaper band.
• On a generator or inverter battery, the gentler startup of an inverter compressor matters, because a small power source can trip on the surge from a fixed-speed unit.
• Many inverter models list a wider operating voltage range, which helps where the supply fluctuates, so check the spec sheet for the range.

Read our guide on the best air conditioner brands suitable for dry heat and humid climates in Nigeria.

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How to Reduce Your AC’s Electricity Use

The fastest ways to cut AC electricity are raising the thermostat setpoint a few degrees, keeping the filters clean, and blocking sunlight from the room.

Each one shortens the time the compressor runs, which lowers the duty cycle and the kWh.

What makes an AC use more or less electricity

• A higher outdoor temperature raises usage, as the above runtime chart shows.
• A lower thermostat setpoint increases run time because the gap to the outdoor temperature is larger.
• Poor insulation, uncovered west-facing windows, and gaps around doors let heat in faster than the unit removes it.
• Dirty filters and coils reduce airflow and heat transfer, so the compressor runs longer for the same cooling.
• A higher-EER or inverter unit uses less power for the same cooling than an older fixed-speed model.

Is it cheaper to leave the AC on or turn it off?

Turning the AC off saves electricity when you will be away for more than a few hours.

For shorter absences, raising the setpoint several degrees is the safer choice, and the startup surge is not what decides it. 

Ask yourself the questions below; the answers will determine your action:

1. Will you be gone for more than a few hours? Turn it off, or, on an inverter model, set it several degrees higher. The longer the absence, the more switching off saves.
2. Is the room sun-exposed or poorly insulated, and will you be back within an hour or two? Raise the setpoint instead, so the room does not heat up and force a long full-power cooldown.
3. Is it a fixed-speed unit? The startup surge lasts a few seconds and uses very little energy compared to an hour of running, so it is not a reason to leave the unit on.
4. Are you on a generator or a small meter? Choose a higher setpoint over repeated on-and-off cycles, because the surge can trip a small supply.

AC vs fan electricity use

An AC uses far more electricity than a fan, but a fan only moves air and does not lower the room’s temperature.

Appliance	Typical draw	Average per hour
Ceiling fan	15 to 75 W	0.015 to 0.075 kWh
Pedestal fan	40 to 70 W	0.04 to 0.07 kWh
1.5HP AC	1,200 W while running	about 0.72 kWh (hot day)

A 1.5HP AC at its running draw uses as much power as 16 to 80 ceiling fans. Fan wattages are typical label ranges, so check your own model.

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Can you run an AC on a generator, inverter battery, or solar?

Yes, if the power source can handle the AC’s starting surge as well as its running draw.

A fixed-speed unit needs a source sized for the surge, and an inverter unit, which starts more gently, often runs on a smaller one.

Generator sizing: running vs starting watts

A fixed-speed air conditioner needs a generator sized for its starting surge, not just its running draw, and the guide on generator size for an air conditioner covers the full calculation.

Unit	Running draw	Estimated starting draw (2 to 3×)	Suggested minimum generator (AC alone)
1HP	0.9 kW	1.8 to 2.7 kW	3 kVA
1.5HP	1.2 kW	2.4 to 3.6 kW	3.5 to 4 kVA
2HP	1.8 kW	3.6 to 5.4 kW	5 to 6.5 kVA

These are rules of thumb for fixed-speed units. Check the starting current on your spec sheet, and add the other loads you will run at the same time.

Battery and solar sizing rule of thumb

1. Work out the daily kWh from the daily table above. A 1.5HP unit used 8 hours at the hot-day average needs about 5.8 kWh.
2. Decide how much runs from the battery. For a night-only AC, the battery must supply the whole 5.8 kWh.
3. Divide the battery kWh by the usable depth of discharge. At 80%, 5.8 ÷ 0.8 gives about 7.2 kWh of battery capacity.
4. Size the panels by dividing daily kWh by peak sun hours and system efficiency. With 5 peak sun hours and 75% efficiency, 5.8 ÷ (5 × 0.75) gives about 1.5 kW, or around four 400 W panels.
5. Choose an inverter rated above the AC’s starting surge, not just its running draw.

These figures are illustrative. The full sizing method is in this guide on how many solar panels to run an AC.

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Measure it yourself. Download the printable 24-hour measurement sheet and record your own AC’s actual kWh and duty cycle: Get the AC usage worksheet.

Knowing how much electricity an AC uses is easier once you can put your own hours, rate, and unit size into the numbers. 

The AC power consumption calculator turns the kWh per hour, per day, and per month figures on this page into a result for your setup.

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Frequently asked questions