What Size Breaker For AC Unit? Explanation + Calculator + Chart

The wrong AC breaker will fry electric circuits. Everybody knows that you have to think about what size breaker you need for an AC unit. Not everybody, however, knows how to adequately choose the right size breaker for an AC unit.

To help you out with AC electrical requirements (and prevent your breaker from catching fire), we have prepared an overview article about air conditioners and respective breaker sizes for different capacity AC units.

ac breaker sizes in amps
Breaker size options for air conditioners include 15A, 20A, 25A, 30A, 35A. Bigger 5+ ton units require up to 65A breakers.

Most homeowners usually need help with determining the breaker size for 220/240V breakers. For smaller 1-ton (or up to and including 15,000 BTU) AC units, you only need a standard 110/120V circuit with the standard 15 amp breaker.

In order to understand the AC breaker sizing, we will look into:

  • How to figure out what size breaker you need for your AC? You can either check the AC label for ‘Max Breaker Size’ in the specification sheet (breaker amps are usually categorized under ‘Overcurrent Protective Device’ section).
    breaker size for 24000 btu air conditioner
    This is a snapshot from a specification sheet for 24,000 BTU (2-ton) AC unit. You have a specified min. circuit ampacity of 18 amps. This AC will fry a 15A breaker. That’s why we need a 20A breaker because it can handle 18+ amps.
  • How to calculate the AC breaker size? Further on, you will find an AC breaker size calculator that includes the bigger units that require a 220/240V circuit.
  • AC breaker size chart for air conditioners with 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5-ton capacity. These units require anything between a 15 amp breaker and a 35 amp breaker. You can find the summarized AC breaker chart at the end.
inappropriate ac breaker size catching on fire
If you choose an AC breaker that is too small (lower-than-needed minimum ampacity), you are running a risk of the breaker catching fire.

First of all, however, let’s look into how to adequately estimate the minimum amps for an AC breaker. This accounts for:

  1. Max. wattage. 1-5 ton units require anywhere between 1,800W and 6,000W electric power input.
  2. NEC breaker requirements. We will lay out the 80% National Electric Code (NEC) requirement for all breakers. This is a safety measure put in place in order to avoid the electric circuit from being overpowered.

Let’s first look at how the determine the minimum AC breaker size:

How To Calculate How Many Amps Breaker Size You Need For AC Units?

The easiest way to figure out how big a breaker you need for AC is to check the AC label. In the photo above, you see an example of the specs sheet with the outlined min. circuit ampacity.

Now, if you don’t have that, you have to know how to calculate the minimal amps of your breaker size.

Here’s how you do that in 2 steps:

  1. Figure out max. the wattage of your AC. You can check the label for maximum wattage. Max. wattage can also be calculated from the EER rating (we presume 10 EER rating in all our calculations further on). Based on this, you can calculate how many amps an AC unit draws.
    breaker size depends on maximum wattage of an air conditioner at full load
    If you have a watt-meter at home, you can even use it to measure the watt or amp draw at 100% output capacity.
  2. When you have the amp draw, you have to apply the 80% NEC rule. This states that the calculated amp draw should represent at most 80% of the total ampacity of the AC breaker.

Calculating Max. AC Wattage

Let’s first illustrate how to calculate the amp draw of an AC unit. Let’s say we have a 24,000 BTU air conditioner. You can get the max. wattage from the label.

Without that, we can approximate the wattage by applying an energy-efficient rating (EER rating of that). A 24,000 BTU AC unit with a 10 EER rating has a max. wattage of 2,400W. Here is how you calculate this:

Max. AC Wattage = Capacity (in BTUs) / EER rating

In our example, the max. wattage calculation looks like this:

Max. AC Wattage (24,000 BTU Unit) = 24,000 BTU / 10 EER = 2,400W

Calculating AC Amp Draw For Breaker Size

When we have the max. wattage, we have to calculate how many amps does such an AC unit draw when running at 100% output. Luckily, we know that these units run on 220V voltage (this may also be a 230V or 240V circuit).

what size breaker do i need for ac unit
Example of breakers that run on 220V electric circuit.

To calculate the amp draw we are going to use to determine the AC breaker size, we use the simple electric power equation:

P = I × V

This is the watts = amps × volts equation. Let’s express I (current) that is measured in amps:

I = P / V

Now let’s use our 24,000 BTU breaker size example. We know that P = 2,400 watts and V = 220 volts. Let’s plug this in the equation:

I (Amp Draw Of 24,000 BTU AC) = 2,400W / 220V = 10.91 Amps

This means that such an air conditioner should at most draw little less than 11 amps of electric current (10.91A, to be exact).

Now, we have to apply the 80% NEC rule. This is a safety measure so you don’t fry your AC breaker.

Apply 80% NEC Rule To Get The Minimal AC Breaker Capacity

This NEC rule tells us that the calculated amp draw should represent at most 80% of the AC breaker size amps. In short, we need a bit bigger AC breaker than the expected max. amp draw (just in case).

Example: Let’s say we have an AC unit with max. amp draw of 8A. This 8A should represent at most 80% of the AC breaker ampacity. That means that we need at least a 10A breaker size.

We can easily account for this 80% NEC rule by multiplying the max. amp draw by 1.25 factor like this:

Breaker Size (Applying 80% NEC Rule) = 8A × 1.25 = 10A

If we check out 24,000 BTU AC unit from the example above, we know that the max. amp draw is 10.91A. To illustrate how to apply the 80% rule here as well, let’s calculate the breaker size for 24,000 BTU breaker:

24,000 BTU AC Breaker Size (Applying 80% NEC Rule) = 10.91A × 1.25 = 13.64 Amps 

This is the minimal breaker size we need. Of course, there is no 13.64A breaker. Breaker sizes are usually rounded to the 5A. Namely, we have 10A, 15A, 20A, 25A, 30A, 35A AC breakers.

If we need a minimum ampacity of 13.64A. That means the 10A breaker is too small. 20A breaker is overkill (you can still use it, of course). The optimum choice of a breaker size for a 24,000 BTU air conditioner is a 15A breaker.

Below, we calculated the minimum required breaker size for 2-ton, 3-ton, 4-ton, and 5-ton air conditioners. You will find the full chart with minimum breaker sizes and actual AC breaker size choices.

This calculation does seem a bit complex for some homeowners. To make your life easier, you can use this automatic calculator that determines the minimum AC breaker ampacity for your air conditioner:

AC Breaker Size Calculator

Here you simply insert the tonnage of your AC and get the minimal breaker size amps. Based on this, you can choose the right size breaker for your air conditioner. (Note: We use a 10 EER rating and 220V to calculate the max. wattage in this calculator)

 

Here is how this AC breaker ampacity calculator works:

Let’s say we have a 3.5-ton AC unit. That’s 42,000 BTU. If the EER rating is 10, it draws 4,200W of power when running at 100%. At 220V voltage, this means it draws 19.09 amps. We need to apply the 80% NEC rule, and we get the minimum breaker ampacity should be 23.86A. That means you will need a 25A breaker for a 3.5-ton AC unit.

The calculator does all this automatically like this:

what amp breaker for a 3.5 ton air conditioner

You can make this calculation yourself for any air conditioner.

We made calculations for 2-ton, 3-ton, 4-ton, and 5-ton air conditioners as well. At the end, you can find a summarized chart for all AC tonnages.

24,000 BTU Air Conditioner Breaker Size (2-Ton Units)

24,000 BTU air conditioners can draw anywhere from 2,000W to 2,800W of electric power when running at 100% output. On average, at a 10 EER rating, they require 2,400 watts to run.

All 24,000 BTU AC units run on 220/240V circuit. We can use 220V for a conservative AC breaker size for 24,000 BTU units.

If we use the breaker size calculator above (that presumed 10 EER rating), we have to have a breaker size that can handle 2,400W at 220V. Here is the required minimum amps of a breaker we get with the calculator (24,000 BTU is equal to 2 tons):

24000 btu breaker size for air conditioner

As you can see, we can confirm that we need a 13.64A minimum ampacity. That means we will need a 15A breaker for a 24,000 BTU air conditioner.

Of course, more energy-efficient 24,000 BTU units run on lower wattage and less energy-efficient units run on higher wattage.

Higher energy efficiency: If the 24,000 BTU unit runs on 2,000W, we need fewer amps. At 220V, the amp draw is 9.09A. Accounting for the 80% NEC rule, this results in an 11.36A minimum breaker size requirement. We still need a 15A breaker.

Lower energy efficiency: If the 24,000 BTU unit runs on 2,800W, we need more amps. At 220V, the amp draw is 12.73A. Accounting for the 80% NEC rule, this results in a 15.91A minimum breaker size requirement. In this case, we need a 20A breaker.

Let’s make similar breaker size calculations for other AC sizes:

What Breaker Size For 3 Ton AC Unit?

On average, 3-ton units (or 36,000 BTU) run on 3,600W. Less efficient units can run on 4,200W and more efficient ones run on as little as 3,000W.

Using the calculator above, we can see that an average 3-ton AC unit requires a breaker with at least 20.45A ampacity. That means the most appropriate choice of a breaker size for a 3-ton unit is a 25A breaker.

Here is the breakdown for high energy efficiency (above 10 EER) and low energy efficiency (below 10 EER) 3-ton units:

  • High energy efficiency 3-ton units will require a 15A breaker.
  • Low energy efficiency 3-ton units will require a 20A breaker.

What Breaker Size For 4 Ton AC Unit?

On average, 4-ton units (or 48,000 BTU) run on 4,800W. Less efficient units can run on 5,600W and more efficient ones run on as little as 4,000W.

Using the calculator above, we can see that an average 4-ton AC unit requires a breaker with at least 27.27A ampacity. That means the most appropriate choice of a breaker size for a 3-ton unit is a 30A breaker.

Here is the breakdown for high energy efficiency (above 10 EER) and low energy efficiency (below 10 EER) 4-ton units:

  • High energy efficiency 4-ton units will require a 25A breaker.
  • Low energy efficiency 4-ton units will require a 35A breaker.

What Breaker Size For 5 Ton AC Unit?

On average, 5-ton units (or 60,000 BTU) run on 6,000W. Less efficient units can run on 6,800W and more efficient ones run on as little as 5,200W.

Using the calculator above, we can see that an average 5-ton AC unit requires a breaker with at least 34.09A ampacity. That means the most appropriate choice of a breaker size for a 5-ton unit is a 35A breaker.

Here is the breakdown for high energy efficiency (above 10 EER) and low energy efficiency (below 10 EER) 3-ton units:

  • High energy efficiency 5-ton units will require a 35A breaker.
  • Low energy efficiency 5-ton units will require a 40A breaker.

Let’s summarize all these breaker sizes for air conditioners:

AC Breaker Sizes Chart (For 1.5-Ton To 5-Ton Units)

Here is the chart for AC breaker sizing (at a 10 EER rating and 220V circuit):

Air Conditioner Tonnage: Max. Wattage (At 10 EER): Amp Draw At 220V: Min. Breaker Ampacity: Min. Breaker Size
1.5 Ton 1,800 Watts 8.18 Amps 10.23 Amps 15 Amp Breaker
2 Ton 2,400 Watts 10.91 Amps 13.64 Amps 15 Amp Breaker
2.5 Ton 3,000 Watts 13.64 Amps 17.05 Amps 20 Amp Breaker
3 Ton 3,600 Watts 16.36 Amps 20.45 Amps 25 Amp Breaker
3.5 Ton 4,200 Watts 19.09 Amps 23.86 Amps 25 Amp Breaker
4 Ton 4,800 Watts 21.82 Amps 27.28 Amps 30 Amp Breaker
4.5 Ton 5,400 Watts 24.55 Amps 30.69 Amps 35 Amp Breaker
5 Ton 6,000 Watts 27.27 Amps 34.09 Amps 35 Amp Breaker

Hopefully, you can use the know-how of how to calculate the breaker sizes to adequately select the right size amp breaker for your AC unit. With the calculated chart, you can quite accurately estimate the electric breaker size requirements for AC units with different capacities (tonnages).

2 thoughts on “What Size Breaker For AC Unit? Explanation + Calculator + Chart”

  1. Cooling Amps:6.3
    Cooling Watts:670
    Heating Amps:11
    Heating Watts: 1260
    Dimensions (WxDxH):18.44″

    Hi, I really need your advice. Will a 15,000btu window ac (specs above) be safe on a 15 amp. circuit breaker. I seem to get conflicting info and I’m concerned with safety.

    Reply
    • Hello Anna, you can load at most 12 amps on a 15 amp circuit breaker (NEC 80% rule). So, you will have absolutely no problems with cooling since that’s only 6.3 amps. Heating does draw 11 amps but that is still less than 12 amps. All in all, with these specs, you are safe to use the 15 amp circuit. Hope this helps.

      Reply

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