How much electricity does an air conditioner use?

As it is commonly known, air conditioners consume a lot of energy, especially in extreme temperatures. But how much electricity does an air conditioner use exactly?

In this article, I’ll put the electricity usage of air conditioners into perspective, which will be especially helpful if you’re thinking about running your AC unit on something other than grid power. Before I get into it, I’ll first clarify the difference between energy and power.

Power vs Energy: The difference between a kW (kiloWatt) and a kWh (kiloWatt-hour)

kiloWatts (kW) and kiloWatt-hours (kWh) are often used interchangeably as if they were the same thing, which doesn’t really hurt until you’re trying to put a system together (solar, batteries, generators, inverters, etc…). And the same goes for power and energy.

Here’s a very simple explanation of what the difference is:

Energy:

Electrical Energy is conventionally measured in Wh (Watt-hours) or kWh (kiloWatt-hours), with 1 kWh = 1000 Wh.

When a utility company bills you, it doesn’t bill you based on how much electrical power your appliances use, but rather on how much electrical energy your appliances consume. This is why you pay for kWh (kiloWatt-hours) rather than kW (kiloWatts).

For example, you could say that the average American household consumes 1000 kWh of energy per month. Or you could say that a mini-fridge consumes around 0.6 kWh per energy per day.

Notice that energy consumption is related to time. In other words, when you say that an appliance consumed a certain amount of energy, you’ll have a time frame for that energy consumption.

The energy consumption of an appliance is helpful when trying to size things like solar arrays, batteries, and other energy sources.

Power:

Electrical Power is conventionally measured in W (Watts) or kW (kiloWatts), with 1 kW = 1000 Watts.

Electrical Power is the rate at which electrical energy is being consumed or produced, at a given moment. For example, you could say that a light bulb uses 60 watts of power when it is on. Or you could say that a refrigerator uses between 200 and 300 watts of power when it is running.

The wattage rating of an appliance is helpful when sizing things like wires, fuses, circuits breakers, inverters, etc…

Sometimes, the power usage of an appliance is not specified by the manufacturer. However, most – if not all – appliances come with a technical specification sticker that includes the voltage (electrical potential) and amperage (electrical current) of the device.

The measurement units for voltage and amperage are Volts and Amps respectively. The relationship between power, voltage, and amperage is:

Power (Watts) = Voltage (Volts) x Amperage (Amps)

The relationship between Power (watts) and Energy (Watt-hours)

As mentioned above, electrical power is the rate at which electrical energy is being consumed or produced.

For example, consider a water tank that is being filled at a rate of 10 gallons per hour. If our tank continues to be filled at this rate for 3 hours, we could figure out how much water has been added to it at the end of those 3 hours:

Added Water (Gallons) = Rate (Gallon/hour) x Time (hours)

Added Water (Gallons) = 10 Gallon/hour x 3 hours

Added Water (Gallons) = 30 Gallons

The same logic goes for electrical power and energy. The relationship between the two can be represented by this equation:

Electrical Energy (Watt-hours) = Electrical Power (Watt) x Time (hours)

For example, consider a lightbulb that has a power rating of 60 Watts. If this light bulb is left on for 5 hours, how much energy would it have consumed?

Electrical Energy (Watt-hours) = Electrical Power (Watt) x Time (hours)

Electrical Energy (Watt-hours) = 60 Watts x 5 hours

Electrical Energy (Watt-hours) = 300 Watt-hours

Now that we’ve established these basics, we can look at both the power usage and the energy consumption of air conditioners.

How much power does an air conditioner use?

As mentioned above, electrical power is measured in watts. So the question becomes: how many watts does an air conditioner use?

The amount of power that an air conditioner uses depends mainly on its BTU (British Thermal Units) rating, the higher the BTU rating, the more power the AC uses. For example, while a 24000 BTU (2 ton) air conditioner uses around 2000 watts, a 36000 BTU (3 ton) AC unit uses around 3000 watts.

It’s also important to note that newer air conditioners are significantly more efficient, meaning they use less power and energy to run at the same capacity. This “efficiency” is indicated by a SEER or EER rating (12 EER for example).

This efficiency can actually be used to calculate the specific power usage of your unit. But before I explain how that goes,  here’s a table that gives you an idea about the power usage of air conditioners based on their capacity:

BTU rating Est. Power Usage 
5000 BTU 400 – 600 Watts
6000 BTU 500 – 750 Watts
8000 BTU 650 – 1000 Watts
12000 BTU (1 ton) 1000 – 1400 Watts
18000 BTU (1.5 tons) 1500 – 2200 Watts
24000 BTU (2 tons) 1800 – 2800 Watts
36000 BTU (3 tons) 2600 – 4500 Watts
Estimated power usage of air conditioners based on their capacity.

Please note that these figures as still just estimates. You can, however, use the information provided by the manufacturer to determine the power usage of your air conditioner.

Generally, there are a couple of ways to do this:

1- Use the Capacity and Energy Efficiency Ratio (EER) of your air conditioner:

Air conditioners will usually have an Energy Efficiency Ratio (EER) rating, and this rating can be used to estimate the power usage of the unit:

Power Usage (Watts) = BTU Rating ÷ EER

Both of these ratings are usually provided within the EnergyGuide label that comes with your AC. For example, the following label is for a 10000 BTU air conditioner that has an EER of 11:

How much electricity does an air conditioner use

The power usage of this air conditioner can be calculated as such:

Power Usage (Watts) = BTU Rating ÷ EER

Power Usage (Watts) = 10000 BTUs ÷ 11

Power Usage (Watts) = 909.1 Watts

Some EnergyGuide labels only provide a Seasonal Energy Efficiency Ratio (SEER) rating, which is not the same as and should not be confused with the EER rating of your air conditioner.

In this case, you can use this (provided by the U.S. DOE) equation to calculate the EER rating of your AC unit:

EER = (1.12 × SEER) – (0.02 × SEER²)

For example, if you have a 12000 BTU air conditioner, and the yellow label specifies a SEER rating of 22, its EER rating can be calculated as such:

EER = (1.12 × SEER) – (0.02 × SEER²)

EER = (1.12 × 22) – (0.02 × 22²)

EER = 14.96

The power usage of this AC is:

Power Usage (Watts) = BTU Rating ÷ EER

Power Usage (Watts) = 12000 BTUs ÷ 14.96

Power Usage (Watts) = 802.14 Watts

In case you can’t find the EnergyGuide label, you can still use the electrical specifications of your air conditioner.

2- Use the Voltage and Amperage specified on your air conditioner:

As previously mentioned, the power usage of an appliance can be calculated using its voltage and amperage:

Power (Watts) = Voltage (Volts) x Amperage (Amps)

While most appliances in the U.S. (including small air conditioners) operate at 120 Volts, large central air conditioners require 240 Volts to operate.

The amperage of the unit will depend on its capacity and efficiency, and will usually be specified under Amps, Current, or RLA for (Rated Load Amps) for bigger air conditioners. These specs can be found in the technical specification sticker, which is usually stuck somewhere on the AC unit.

For example, here’s a specification label for a 5000 BTU unit:

How much electricity does an air conditioner use

This particular specification sticker provides the wattage of the unit, which is pretty useful. But in case it didn’t, the wattage can still be calculated as such:

Power (Watts) = Voltage (Volts) x Amperage (Amps)

Power (Watts) = 115 Volts x 4 Amps

Power (Watts) = 460 Watts

Here’s another example of a much bigger AC unit, where the wattage is not directly specified:

How much electricity does an air conditioner use

The image above shows the technical specifications of a 36000 BTU central air conditioner. The Rated Load Amps for this AC unit is 14.4 Amps and its voltage says 208/230V, which means that its voltage is 240 Volts.

As a general rule of thumb, the power usage of this air conditioner can be calculated as such:

Power (Watts) = Voltage (Volts) x Amperage (Amps)

Power (Watts) = 240 Volts x 14.4 Amps

Power (Watts) = 3456 Watts

The actual power usage of this particular unit will be lower than 3456 watts (because of its power factor), however, overestimating is better than underestimating in this case.

How much energy does an air conditioner use?

The energy consumption of an air conditioner not only depends on its rated capacity and efficiency but also on other factors such as:

  • Usage time
  • Outdoor temperature
  • Quality of insulation

This makes it very hard to calculate – with precision – the amount of energy that an air conditioner consumes based on its power usage and usage time.

However, to put things into perspective, the following table provides estimates of the hourly energy usage of air conditioners based on their BTU ratings:

BTU rating Est. Hourly Energy Consumption (kWh/hour) 
5000 BTU 0.25 – 0.4 kWh/hour
6000 BTU 0.3 – 0.5 kWh/hour
8000 BTU 0.4 – 0.65 kWh/hour
12000 BTU (1 ton) 0.6 – 1 kWh/hour
18000 BTU (1.5 tons) 0.8 – 1.5 kWh/hour
24000 BTU (2 tons) 1 – 1.8 kWh/hour
36000 BTU (3 tons) 1.5 – 2.8 kWh/hour
Estimates of the hourly energy consumption of air conditioners based on their capacity.

How to estimate the energy consumption of your air conditioner?

As mentioned before, the energy consumption of an appliance can be calculated using its power usage and usage time:

Electrical Energy (Watt-hours) = Electrical Power (Watts) x Time (hours)

This is pretty straightforward for appliances that run 100% of the time when you turn them on (light bulbs, TVs, laptops, etc…). However, this is rarely true in the case of air conditioners.

Let me explain.

We can generally define 2 types of air conditioners, non-inverter units, and inverter units.

Non-inverter air conditioners:

When these AC units are turned on, they operate at full capacity (compressor runs at full speed) until the set temperature is reached. Once the set temperature is reached, these ACs turn off and then turn back on when the temperature starts rising again. They keep turning on and off in this way to maintain the set temperature.

The amount of time for which these air conditioners are actually running is referred to as a Duty Cycle, and this duty cycle depends on how easy it is to reach and maintain the set temperature.

For example, consider a non-inverter 5000 BTU air conditioner that is rated at 450 Watts.

With average insulation and temperatures around 90°F, this air conditioner will probably have a duty cycle of 75%, meaning that it really only runs for 45mins for every hour that it is on.

If it’s left on for 4 hours, its energy consumption can be calculated as such:

Electrical Energy (Watt-hours) = Electrical Power (Watts) x Time (hours) x Duty Cycle

Electrical Energy (Watt-hours) = 450 Watts x 4 hours x 75%

Electrical Energy (Watt-hours) = 450 Watts x 4 hours x 0.75

Electrical Energy (Watt-hours) = 1350 Watt-hours

However, there’s no practical way to determine the actual duty cycle of this AC. Such calculations will – at best – result in rough estimates.

Inverter air conditioners:

These air conditioners are equipped with an inverter that allows their compressor to run at different speeds based on cooling demands.

When you turn on one of these AC units, it’ll run at full capacity until the set temperature is achieved, and then run at lower speeds to maintain the temperature.

For example, consider a 12000 BTU inverter mini-split air conditioner that is rated at 900 Watts.

When this AC unit is first turned on, it’ll use 900 Watts of power until the set temperature is reached, and then it’ll run at around 200-400 Watts for most of the time. If a door or a window is opened, the air conditioner will draw more power to bring the temperature back down.

Although they stay ON all the time, these air conditioners have proven to be at least 30% more efficient than non-inverter units. However, it is still hard to come up with estimates for their energy consumption.

The only way to estimate the energy consumption of an AC is to use rules of thumb.

For example, consider a worst-case scenario in which the insulation is bad, and the temperature exceeds 95°F. In this case, the air conditioner will probably stay on (or operate at full speed) 100% of the time. The energy consumption in this scenario could be calculated as such:

Electrical Energy (Watt-hours) = Electrical Power (Watts) x Time (hours)

In a best-case scenario, where the insulation is great and the temperature is only about 85°F, the air conditioner would – for example -only stay on 40% of the time (or operate at 40% of its rated power on average). In this scenario, an estimate can be calculated as such:

Electrical Energy (Watt-hours) = Electrical Power (Watts) x Time (hours) x 40%

In any case, the most precise way to determine the energy consumption of an air conditioner is to actually measure it.

How to measure the energy consumption of your air conditioner?

Thanks to electricity monitoring devices, you can measure the exact amount of energy that an air conditioner consumes over time.

If your air conditioner connects to the wall outlet (or an inverter), you can use the Kill-A-Watt meter to measure its energy consumption over a certain period of time.

All you have to do is plug the device into the outlet, and then plug your AC unit into it.

How much electricity does an air conditioner use

For example, the following video shows a 5000 BTU window air conditioner that consumed 1.6 kWh of energy over 3 hours and 30 minutes.

If you have a central air conditioner that operates at around 220 Volts, and that runs on a dedicated circuit, you can use the Emporia monitor.

This device will be installed in your main electrical panel and will send real-time data to a monitoring app on your phone or tablet. However, unless you’re qualified, please get an electrician to set up the device for you.

In any case, the following video explains how the Emporia monitor works:

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Younes
Younes

Hi! My name is Younes. I'm an electrical engineer and a renewable energy enthusiast. I created renewablewise.com with a mission of delivering digestible content and information to the people who seek it.

One comment

  1. Hi Younes, i am asif masood a chemical engineer by profession. Than you for sharing a detail insight on how we can check & monitor Split Unit ac power consumption .

    If you can not measure it, you can not control it 🙂

    Regards

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