How much does your AC really cost to run? Free running cost calculator

A typical room air conditioner costs about 8 to 30 cents an hour to run at $0.15 per kWh, and a central system costs about 45 to 53 cents.

The AC running cost calculator below turns that range into your own number from three inputs: how much power your unit draws, how long it runs, and what your utility charges per kWh.

Most calculators stop there and then disagree with your bill. Three corrections close the gap: converting BTU or tonnage into real watts, adjusting for the time the compressor actually runs, and using the rate your AC is billed at, which is often higher than your average rate.

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AC running cost calculator

An air conditioner running cost calculator multiplies your unit’s electrical draw in kilowatts by the hours it runs and your price per kWh.

This one adds two inputs most tools leave out: a run-time factor that reflects how hard the compressor actually works, and an optional peak rate.

Enter capacity in BTU, tons, or kW of cooling, then an efficiency rating (EER, SEER, SEER2, or an Indian star label) or your unit’s watts if you know them.

Add hours per day, days per month, your rate, and your currency. The result shows cost per hour, day, month, and cooling season, along with the kWh behind each figure.

What to enter and where to find it on your AC

1. Find the capacity on the unit’s nameplate or in the manual. It appears in BTU per hour, tons, or kW of cooling, and one ton equals 12,000 BTU per hour.
2. Find the efficiency rating on the same label: EER, SEER, SEER2, or the star label. If the label lists input watts, use that number and skip the rating.
3. Read your rate from your latest bill as a price per kWh. If the bill shows separate peak and off-peak prices, enter both.
4. Estimate the hours per day and days per month the AC is switched on. Count switched-on hours, not compressor hours, because the run-time factor handles the difference.
5. Leave the run-time factor at its default until you have measured your own, which the end of this guide explains.

If you only know the room and not the unit, the BTU AC calculator estimates the capacity you need first.

Worked example: a 12,000 BTU AC running 8 hours

1. Divide capacity by efficiency: 12,000 BTU per hour ÷ EER 10 = 1,200 W, or 1.2 kW.
2. Multiply by hours: 1.2 kW × 8 hours = 9.6 kWh at full draw.
3. Multiply by your rate: 9.6 kWh × $0.15 = $1.44 for the day at full draw.
4. Apply a run-time factor of 0.6, a planning estimate for a mild day: 9.6 × 0.6 = 5.76 kWh, or about $0.86.

Central AC running cost calculator

Select central in the type menu and the calculator switches to tons (2 to 5), SEER2 or EER2, and cooling season length.

Central systems draw about 3 to 3.5 kW, so an 8-hour day at full draw costs roughly $3.60 to $4.20 at $0.15 per kWh.

Duct leaks and poor installation raise the real figure, which the section on room and installation quality covers.

Split AC running cost calculator

The split preset takes capacity in BTU, tons, or kW, with inverter on by default and a switch for fixed speed.

Expect an input draw of roughly 1 to 2 kW. Let’s say a Split AC unit in the UK uses 2 kW, while a 1.5-ton figures run from 0.8 to 1.5 kWh per hour depending on inverter technology and star rating.

Please, if you are reading this from India, kindly enter the star label instead of an EER.

Window AC running cost calculator

The window preset covers window and portable units from 5,000 to 12,000 BTU and asks for an EER.

An 8,000 BTU window unit at EER 11 draws about 727 W (8,000 ÷ 11).

Window units usually cool one room, so hours of use tend to be lower than for a central system, which is why the monthly cost often lands far below it.

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How can I calculate the Running Cost of my air Conditioner? (formula explained)

You calculate it in three steps: convert the unit’s rating into watts, multiply by the hours it runs, then multiply by your electricity price per kWh.

The first step is where most people go wrong, because BTU and tons measure cooling output, not power.

The Core Formula: Watts × Hours × Rate

Running cost = (watts ÷ 1,000) × hours × price per kWh.

A kilowatt-hour (kWh) is one kilowatt of power used for one hour, and it is the unit your utility bills you in.

The rate is the price of one kWh on your bill. A 1,200 W AC running for 5 hours uses 6 kWh, and at $0.15 per kWh that costs $0.90.

For a wider look at what drives those watts, see how much electricity an AC uses.

Convert BTU, Tons, or KW Cooling into Electrical Watts

Capacity is not power: a 12,000 BTU AC does not draw 12,000 W. Divide the BTU rating by the EER to get input watts, using 1 ton = 12,000 BTU per hour.

Capacity (BTU/h)	Tons	Cooling kW	Watts at EER 8	Watts at EER 10	Watts at EER 12	Watts at EER 14
5,000	0.42	1.47	625	500	417	357
8,000	0.67	2.34	1,000	800	667	571
18,000	1.5	5.28	2,250	1,800	1,500	1,286
24,000	2	7.03	3,000	2,400	2,000	1,714

To convert a nameplate you already have, the BTU-to-watts calculator does it in one step.

Why “hours on” is not “hours at full power”

A fixed-speed compressor cycles. Once the room reaches the thermostat setting, the compressor shuts off while the fan keeps running, then restarts as the room warms.

An inverter unit does something similar without stopping: it slows the compressor and draws less power.

Either way, eight hours switched on is not eight hours at the rated draw, so the basic formula overstates the bill.

This calculator uses a run-time factor: the share of full rated power your AC averages while it is on.

Multiply the rated kWh by that factor, and you get the equivalent of full-power hours. In the 12,000 BTU example, 9.6 kWh at full draw becomes 5.76 kWh at a factor of 0.6.

The factor moves with the weather. On a mild evening, the compressor may run less than half the time, while on a 100°F afternoon it runs close to all of the time.

A reasonable planning range is about 0.4 to 0.6 in mild weather and 0.8 to 1.0 in peak heat, with inverter units usually sitting lower because they modulate.

Treat those as editorial estimates rather than measured standards, since insulation, sun exposure, and setpoint all shift them.

The reliable way to get your own figure is to measure it, and the steps for that come near the end of this guide.

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How much does it cost to run an air conditioner per hour, day, and month?

A room AC costs about 8 to 30 cents per hour at $0.15 per kWh, and a central system about 45 to 53 cents.

At 8 hours a day, a month runs from roughly $18 for a small window unit to about $126 for central cooling. Those figures assume full draw, so real bills usually come in lower.

How much does it cost to run AC for an hour? (hourly cost calculator)

Cost per hour is the unit’s kilowatts times your rate. At 1.2 kW and $0.15 per kWh, that is $0.18 an hour at full draw.

The hourly mode of the calculator strips the form down to two fields: capacity or watts and your rate, so you get the one-hour figure before you look at the type tables below.

An hour of cooling rarely means an hour of full compressor power, so treat the result as a ceiling and scale it by your run-time factor.

How much does it cost to run AC for a month?

Monthly cost is the hourly cost times hours per day times 30. The grid below assumes full rated draw and $0.15 per kWh, so swap in your own rate and apply your run-time factor to bring the numbers down.

For example, a central units at roughly $30 to $270 a month at 8 hours a day, depending on size, a range that brackets the 3.5 kW row.

Input draw (kW)	4 hours/day	8 hours/day	12 hours/day
0.7	$12.60	$25.20	$37.80
1.0	$18.00	$36.00	$54.00
1.2	$21.60	$43.20	$64.80
2.0	$36.00	$72.00	$108.00
3.5	$63.00	$126.00	$189.00

Cost by AC type: window, portable, split, and central

The table uses $0.15 per kWh and full draw. Central, split, window, and portable ACs are approximate planning figures.

Type	Typical input draw	Per hour	Per 8-hour day	Per 30-day month (8 hours/day)	Best for
Window	500 to 1,200 W	$0.08 to $0.18	$0.60 to $1.44	$18 to $43	One room
Portable	1,000 to 1,400 W	$0.15 to $0.21	$1.20 to $1.68	$36 to $50	Renters and temporary setups
Split (inverter)	800 to 2,000 W	$0.12 to $0.30	$0.96 to $2.40	$29 to $72	One or two rooms with long daily use
Central	3,000 to 3,500 W	$0.45 to $0.53	$3.60 to $4.20	$108 to $126	Whole homes

Cost by size: from 0.75 ton to 5 ton

At a fixed efficiency, cost scales almost linearly with size: each added ton at EER 10 adds about 1.2 kW, or 18 cents an hour at $0.15 per kWh.

Size (tons)	BTU/h	Input kW at EER 10	Per hour	Per month (8 hours/day)
0.75	9,000	0.9	$0.14	$32.40
1	12,000	1.2	$0.18	$43.20
1.5	18,000	1.8	$0.27	$64.80
2	24,000	2.4	$0.36	$86.40
3	36,000	3.6	$0.54	$129.60
5	60,000	6.0	$0.90	$216.00

1 ton AC power consumption per hour

A 1-ton AC (12,000 BTU per hour, about 3.5 kW of cooling) draws roughly 0.86 to 1.5 kWh per hour, depending on its efficiency rating.

EER	Input watts	kWh per hour	Cost per hour at $0.15
8	1,500	1.50	$0.23
10	1,200	1.20	$0.18
12	1,000	1.00	$0.15
14	857	0.86	$0.13

Same AC, four tariffs: US, UK, India and Australia

The same 1.2 kW unit costs about twice as much per hour in the UK as in the US, purely because of the rate.

The rates below are illustrative. To set an example, we use the UK figure using the 24.67p per kWh rate; please confirm the price cap for your locality.

Region	Rate used	Per hour	Per 8-hour day
US	$0.15 per kWh	$0.18	$1.44
UK	24.67p per kWh	29.6p	£2.37
India	₹8 per kWh	₹9.60	₹76.80
Australia	A$0.30 per kWh	A$0.36	A$2.88

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Does efficiency rating change what you pay? EER, SEER2, ISEER and inverter

Yes. Input watts equal cooling output divided by the rating, so moving a 12,000 BTU unit from EER 8 to EER 12 cuts its draw from 1,500 W to 1,000 W, a one-third reduction.

The complication is that each country labels efficiency differently, so the same unit can appear under four different numbers.

EER, COP, SEER, SEER2 and ISEER translator

The table converts each rating into something you can put in the formula. SEER2 replaced SEER for US testing on January 1, 2023, and the same unit scores about 4.7% lower under the new test.

A 16 SEER unit is therefore roughly 15.2 SEER2 (16 × 0.953) with no change in how much power it uses. Canada still labels with SEER.

Metric	What it measures	How to turn it into watts or kWh
EER	Cooling BTU per hour per watt at fixed test conditions	Watts = BTU/h ÷ EER
EER2	EER under the updated US test, measured at 95°F outdoor temperature	Same formula as EER
SEER	Seasonal cooling output per watt-hour across a range of temperatures	Annual kWh ≈ annual cooling BTU ÷ SEER ÷ 1,000
SEER2	SEER under the US test in force since January 1, 2023	SEER2 ≈ SEER × 0.953, then use the SEER formula
COP	Cooling kW per input kW	Input kW = cooling kW ÷ COP, and COP = EER ÷ 3.412
kW per ton	Input kW per ton of cooling	Input kW per ton = 12 ÷ EER
ISEER (India)	Seasonal ratio on the BEE star label	Use the annual kWh printed on the label

If you hold a SEER label and need an EER, the SEER to EER converter handles it.

Inverter AC power consumption calculator

The inverter mode of the calculator replaces the single run-time factor with three bands: hours per day at low, medium, and high output, each with its own draw.

A rough split such as 3 hours low, 3 medium, and 2 high works for a first estimate. If your unit carries an ISEER or star label, you can skip the bands and type the annual kWh from the label for a seasonal figure.

Because an inverter slows its compressor instead of shutting it off, its average draw is lower, and this mode shows that without asking you to guess one blended number.

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What else changes your AC running cost?

Three things move an AC bill beyond the unit’s rating: the thermostat setting, how your tariff charges for peak hours, and the room and installation around the unit.

Room, insulation, sizing, and installation quality

Before blaming the unit, check the room with the AC capacity calculator by room size, because a mismatched size is one of the most common causes of a high bill.

• An oversized unit cools the room quickly, shuts off, and restarts often, which wastes energy and leaves humidity high.
• Poor insulation and sun-facing windows push the compressor toward full-time operation, which raises your run-time factor.
• Installation quality can account for up to 30% of real-world performance; leaky ducts or a wrong refrigerant charge can undo a high rating.
• Dirty filters and coils force the unit to run longer for the same amount of cooling.

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

For sure, it’s cheaper to turn the AC off all day or for a few hours than leaving it on all day long. More hours, more electricity consumption, lower hours, lower electricity consumption- as simple as ABC.

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How to lower your AC running cost

The fastest way to lower AC running cost is to raise the setpoint a few degrees and add airflow. Everything else adds smaller gains.

Seven quick wins, ranked by typical impact

1. Raise the thermostat 2 to 4°F. At 3 to 5% per °F, this is the largest single lever.
2. Add a ceiling or pedestal fan so you can hold the higher setting comfortably.
3. Use the timer or sleep mode so the unit stops cooling an empty or sleeping room at full power.
4. Move heavy use outside peak hours if your plan has time-of-use pricing.
5. Clean filters monthly during heavy use and keep outdoor coils clear of debris.
6. Shade windows and seal gaps so the room gains less heat and the compressor idles longer.
7. Service the system, since installation and charge problems can cost up to 30% of performance.

Our full guide on how to reduce your AC electricity bill covers each step in more detail.

Check the real number: measure your AC instead of guessing

1. For a plug-in unit, connect an energy monitor between the wall outlet and the AC, reset it, run the AC through a normal day, and read the kWh.
2. For a hard-wired or central system, read your electricity meter, run the AC for a set number of hours, and read it again. Take a baseline hour with the AC off and subtract it.
3. Divide the measured kWh by the rated kW times the hours switched on. A unit rated at 1.2 kW that used 5.4 kWh over 8 hours has a run-time factor of 5.4 ÷ 9.6 = 0.56.
4. Enter that factor in the calculator and compare the monthly result with your next bill.

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Get your exact number

Once you have your run-time factor and your peak rate, the figures on this page stop being estimates and start matching your bill.

The same inputs drive the AC power consumption calculator, which shows how many kWh your unit uses per hour, day, and month, so you can check a power consumption reading against your meter and your running cost against your bill.

Run the AC running cost calculator with your own rate.

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Frequently asked questions