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Why are Air-Conditioners (AC) Rated in Tons, Not in kW or kVA?

Why is an Air Conditioner and Refrigerator Rated in Tons instead of kVA or kW?

In today’s comprehensive HVAC technical article, we will discuss and help you gain an understanding of the following basic and important terms and expressions used in heating and cooling devices and applications.

  • Why is an AC Rated in Ton, Not in kW?
  • Definition of Ton
  • How Many kW, kWh and HP are Equivalent to 1 Ton?
  • How to Convert Ton to kW / kWh and vice versa?
  • How Much Current in Ampere Will a 2 Tons AC Draw in 1-Phase & 3-Phase System?
  • How Many 2-Ton Air Conditioners Can I Run on a 30 kVA Generator?
  • What is the Suitable Rating of an MCB for a 1-Ton and 2-Tons Air Conditioner (AC)?
  • and much more…

Comprehensive HVAC Technical Article - Heating, Ventilation, and Air Conditioning


Why is an AC Rated in Ton, Not in kW?

Refrigeration and air conditioning (AC) systems are typically rated in tons. The capacity of an air conditioner is specified in tons instead of kilowatts (kW) or kilovolt-amperes (kVA) because it is designed to remove a specific quantity of heat from a defined area, such as a room or a hall.

Air conditioners are rated in tons rather than kW or kVA because of their historical origins and the way cooling capacity was originally measured. The term “ton” in this context does not refer to weight but rather to the amount of heat required to melt one ton (2000 pounds) of ice in a 24-hour period, which is equivalent to 12,000 British Thermal Units (BTUs) per hour.

This measurement became popular in the early 20th century when ice was commonly used for cooling, and it provided a convenient way to describe the cooling capacity of early air conditioning systems.

Even though the use of ice for cooling has largely been replaced by mechanical refrigeration, the term “ton” has persisted as a unit of measurement for air conditioning capacity. It is a well-established convention in the HVAC (Heating, Ventilation, and Air Conditioning) industry and is still widely used in the United States and some other countries.

While kilowatts (kW) or kilovolt-amperes (kVA) could technically be used to describe the cooling capacity of an air conditioner, the use of tons has become a standard practice and is often preferred for consistency and familiarity within the industry.

The term “ton” in reference to cooling capacity indicates the amount of heat energy a system can remove. If an air conditioner can remove 12000 BTUs (equivalent to 12,660.5 kJ, 30,26 kilocalories, or 3.517 kW-h) of heat in an hour, it is rated as a 1-ton AC unit.

The same measurement of ratings applies to all HVAC (Heating, Ventilation, and Air Conditioning) systems, such as air conditioners (AC), heat pumps, chillers, freezers, refrigeration systems, and cooling towers etc.

Why is an Air-Conditioner (AC) Rated in Ton, Not in kW or kVA?


Good to know:

  • British Thermal Unit (IT) per pound per Fahrenheit degree (Btu (IT)/lb-°F) is a unit of measurement that has the dimension of L2T-2Q-1. Where: L is length, T is time, and Q is temperature.
  • BTU = British thermal unit. A measurement of heat, specifically, the amount of heat needed to raise the temperature of a pound of water by 1°F.
  • 1 BTU = 0.252 kilocalories = 1055.05 joules = 0.293 W-hours = 0.0000833333 – ton.
  • 12000 BTUs/hr = 1 Ton

Related Post: Why is a Transformer Rated In kVA, Not in KW?

Definition of Ton

A Ton of refrigeration (RT) is approximately equivalent to 12,000 BTU/h or 3,516.8528 W or 4.7142Hp.

A Ton of refrigeration (RT) is a unit of power used to describe the heat-extraction capacity of air conditioning and refrigeration equipment. It is defined as the heat of fusion absorbed by melting 1 short ton of pure ice at 0 °C (32 °F) in 24 hours.

In industrial HVAC (Heating, Ventilation, and Air Conditioning), a “ton” is a unit of cooling capacity. It is defined as the amount of heat absorbed or removed by one ton (2000 pounds) of ice melting over a 24-hour period. In terms of BTUs (British Thermal Units), one ton is equivalent to 12,000 BTUs per hour.

For example, a 2-ton air conditioner has a cooling capacity equivalent to 24,000 BTUs per hour, while a 3-ton unit has a capacity of 36,000 BTUs per hour, and so on.

Good to Know: 1 Ton = 12,000 BTU/h = 12,660.5 kilojoules = 30,26 kilocalories = 3.517 kilowatts-hours

How Many kW, kWh and HP are Equivalent to 1 Ton?

1 Ton = 3.5168525 kWh = 4.714Hp


1 Ton = 12,000 BTU/h

1 Watt = 3.412141633 BTU/h

1 Ton = 12,000 ÷ 3.412141633 = 3,516.8528 Watts = 3.5168528 kW.

1 Ton = 3,516.8528 Watts = 3.516 kW.


1 Ton = 3,516.8528W ÷ 746 = 4.7142798928 Hp →→→ (1 Hp = 746 Watts)

1 ton is equivalent to:

  • Approximately 3.517 kilowatts (kW) of cooling capacity.
  • Approximately 3.517 kilowatt-hours (kWh) of energy consumption per hour (assuming a coefficient of performance (COP) of 1, meaning 1 kW of electricity produces 1 kW of cooling).
  • Approximately 4.714 horsepower (HP) of cooling capacity (1 HP is equivalent to 0.7457 kW).

1 Ton = 4.714 Hp

How to Convert Ton to kW / kWh and vice versa?

One RT (Refrigeration Ton) = 3.5168528 kW

1 R= 3.5168528 kWh

1 kWh = 0.284345 RT (Refrigeration Ton)

1 kWh = 0.28434517 RT


The power “P” in kW = Power “P” in RT (Refrigeration Ton) times 3.5168528.

Conversion of Ton into kW

P(kW) = P(RT) × 3.5168528

Conversion of kW / kWh into Tons

P(RT) = P(kW-h) ÷ 3.5168528

Example 1:

Convert 3 Ton AC into kW i.e. Convert 3 RT to kW or kWh.


P(kW) = 3 RT × 3.5168528

P(kW) = 10.55 kW


3 Ton AC = 10.55 kW

So, a 3-ton air conditioner has a cooling capacity of approximately 10.551 kilowatts.

Example 2:

Convert 0.5275 kW or kWh into Tons


P(RT) = 0.5275 kW ÷ 3.5168528

P(RT) ≈ 1.5 Tons


0.5275 kW Ton AC = 1800 BTU = 1.5 Tons of AC

Please note that these formulas assume a coefficient of performance (COP) of 1, meaning 1 kW of electricity produces 1 kW of cooling. In reality, COP varies depending on the efficiency of the cooling system. Adjustments may be needed for systems with different COP values.

How Much Current in Ampere Will a 2 Tons AC Draw in 1-Phase & 3-Phase System?

Current Drawn by 2 Tons AC in a Single Phase Circuit

Suppose, the single phase supply voltage are 230V having a power factor = Cos ϕ = 0.95

1 Ton = 3,516.8528 Watts = 3.516 kW.

2 Ton = 2 × 3.516 kW = 7.032kW = 7032W

Power in a Single Phase AC System

P = V × I Cos Φ and current…

I = P ÷ (V × Cos Φ)….. Where Cos Φ = Power factor

I = 7032W ÷ (230V × .95)

I = 32.18 A

Therefore, a 2 Ton AC (Air-conditioner in Single Phase AC system will draw 31.18 Ampere Current

Current Drawn by 2-Ton AC in a Three-Phase Circuit

Suppose, There are 440V and Power factor = Cos Φ = 0.85 in Three Phase AC system…

Power in a Three Phase AC System

P =√3 × VL × IL CosΦ and current….

I = P ÷ ( √3 × V × CosΦ)

I = 7032W ÷ (1.732 × 440V × .85) Where Cos Φ = Power factor and √3 = 1.732

I = 10.855 A

Therefore, a 2 Ton AC (Air-conditioner in Three Phase AC system will take 10.855 Ampere Current.

Good to Know:

These calculation are based on basic electrical formulas and the assumptions and reference values may change with real life applications. For example, an air conditioner current depends a lot on operating conditions such as ambient temperature, refrigerant pressure, Energy Efficiency Ratio (EER) etc. for instance, if EER is 6, then input power for 2 Tons Air conditioner is 24000BTU/6 = 4000 watts

In case of single-phase 230 volt system, the air conditioner load current would be = 4000 ÷ (230V × .95) = 18.5 A

Another similar rating is Coefficient of power (COP) which is the output power in watts divided by input power, so with a COP = 1.8, for instance, input power for 2 Tons Air conditioner  is 7032W ÷ 1.8 = 3906 watts. Now you can find current by using the above method which is equal to 18A approx. [/box]

How Many 2-Ton Air Conditioners Can I Run on a 30 kVA Generator?

To determine how many 2-ton air conditioners you can run on a 25 kVA generator, you first need to calculate the total power consumption of the air conditioners and compare it to the generator’s capacity.

A 2-ton air conditioner typically requires around 3.516 kW ( ≈ 3500 watts) per hour. Since 1 ton is approximately equal to 3.5 kW, a 2-ton unit would be around 7032W (≈7 kW).

2 Ton = 2 × 3.516 kW = 7.032kW = 7032W

The efficiency of utility power generators are 90% approximately.

Efficiency of Generator = 30 kVA × (90 ÷ 100) = 27 kVA

Now the Number of 2 Ton AC (Air conditioners) which you can run on a 25 kVA Generator smoothly:

27kVA ÷ 7032W = 3.8

So, you can run three air conditioners, each rated at 2 tons, on a 30 kVA generator. Do not add an additional unit to avoid overloading the circuit.

What is the Suitable Rating of an MCB for a 1-Ton and 2-Tons Air Conditioner (AC)?

Note: For calculations in depth, you may refer to the premium technical resource on sizing a circuit breaker for various electrical devices and applications.

Sizing MCB for 1 Ton AC

A 1-ton AC usually has a running current of around 5 to 7 amps and a starting current that could be around 15 to 20 amps or higher. As the starting current is high during the initial switching, hence it takes more current at full load than the normal running current.

1 Ton = 3516.85 W

Full Load Current of 1 Ton AC in 230V AC circuit can be calculated using Ohm’s Law.

I = P ÷ V

3516.85W ÷ 230V

I ≈ 15.3

The circuit breaker should be connected to the load at 80% of its rated amperes. In other words, the rating of the circuit breaker should be 1.25 times the load circuit current.

  • 15.3A Load Circuit × 1.25 ≈ 19.125A Breaker Size
  • 19.125A Breaker × (80/100) = 15.3A Load Circuit

Now, the next standard size of 20A Class “C” MCB (miniature circuit breaker) is perfect for 1 Ton AC (air-conditioner) which is capable to run the AC smoothly in both the full load high starting current as well as the normal running current without tripping the circuit.

And 20 A Class “C” MCB would be better for 1 Ton AC (air-conditioner)

Sizing MCB for 2 Ton AC

A 2-ton AC typically has a running current of around 10 to 12 amps and a starting current (also known as inrush current) that can be significantly higher, possibly reaching 30 to 40 amps or more for a brief period during startup.

As we have calculated the load current for 2 Ton Air conditioner (AC) above which is 32A.

Calculated Current for 2 Ton A.C = I = 32 A

The circuit breaker should be connected to the load at 80% of its rated amperes. In other words, the rating of the circuit breaker should be 1.25 × load circuit current e.g.

  • 32A Load Circuit × 1.25 = 40A Breaker Size
  • 40A Breaker × (80/100) = 32A Load Circuit

Now 40A Class “C” MCB (miniature circuit breaker) would be suitable for 2 Ton AC (air-conditioner) as it will smoothly handle both the high starting starting and ruining current in the circuit.

Good to Know:

Class “’C’ Type of CBs

Class “C” type MCBs are suitable for installations with high inrush current during the initial switching time. In other words, they are ideal for equipment and devices with inductive loads, such as air conditioners, induction motors, fluorescent lamps, transformers , etc.

A general AC (Air-conditioner) Name plate rating Data

A general AC (Air-conditioner) Name plate rating Data
Related Posts:

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    1. @ Junaid Khan…<br />We took it as a reference…in real calculation…you will have to take actual Power factor value…

    2. @electrical technology<br />i am mechanical engineer just graduated and have a very common question which i couldnt ask during my course duration.<br />1 ton= 3.52 kW approx but on our A.c it is written cooling capacity 12000 Btu/hr ( thats 1 ton) but also written Power Consumption 1348 W .. if its 1 ton it have to consume 3520 W for rated cooling? what is point i am not getting from the relation

    3. The calculations are grossly wrong, as One ton of AC means the removal of that much of heat or energy or whatever, it does not mean the consumption of that much of power. In practical cases an AC system to remove one ton of consumes around 1.2KW, moreover the compressor in practical conditions run only for 30% time. I never expected this kind of theoretical mistake in an engineering page.

      1. Power consumed = Heat Rejected – Refrigeration effect (Law of conservartion or Carnot Refrigeration cycle)

        Now,in above calculation,Heat rejection is assumed as zero (PPM1) so Power consumed = Refrigeration effect .

        In actual case EER or COP & Rerigeration effect determine actual Power consumption (as above calculations).

        SO Electrical Technology calculations are perfectly RIGHT one from IDEAL (PPM1) & other from REAL point of view.

        Hope this work !

  1. You have hit on the bulls eye. you article is just amazing and reading it again and again is still not enough. There is some kind of charisma in your article that draws me towards reading it again and again and again

    1. have a project that split type AC with specs 4hp, 2kw electric heater, 1p, 220v, 60 hz, could anyone explain how this electric heater work with the system?

  2. i am mechanical engineer just graduated and have a very common question which i couldnt ask during my course duration.<br />1 ton= 3.52 kW approx but on our A.c it is written cooling capacity 12000 Btu/hr ( thats 1 ton) but also written Power Consumption 1348 W .. if its 1 ton it have to consume 3520 W for rated cooling? what is point i am not getting from the relation

    1. Dear friend ,
      I think your Ac is rated for 3 star energy efficiency ratio it is 2.5 for 3 star (3.5 for 5 star)
      so 1 ton cooling capacity is equal to 3520 w
      divide by 2.5 if your ac is rated for 3 star, divide by 3.5 if your ac is 5 star
      3520 w/ 2.5 = 1408 w power consumption

  3. i have read my orient a.c specification 1 ton with 1950W.but here in calculation your result is 3150W….what wrong with these.can anyone explain

  4. I am a consumer of Calcutta Electric Corporation. In my electric Bill Load (KVA) is written as 0.9. Whether this load is sufficient for running one 1.00 Ton Air Conditioner ?<br />MAdhab Char

  5. Note the claculation to as below : <br />If 1 TR = 1000 K Cal / Hr ….then it is =1000*4.18/3600 = 1.2 KW.<br />Actually,<br />1 TR = 3024 K Cal / Hr……that comes to =3024*4.18/3600 = 3.5 KW.<br /><br />This is the thermal power equivalent of 1TR by definition.

  6. The clarification above for converting TR to electrical power is not correct. 1 TR is equal to 3516 W is not electrical power. It is mechanical power. we need find out how much electrical power required to generate that much mechanical power. 1.7kW split type air conditioner can generate 1 TR or 3.516 Mechanical KW.

    1. Your question is wrong. Everyone here is just guessing and discussing wrong calculations.
      Cooling capacity means the amount of heat energy that can be pumped from inside of the room (usually low temperature) to outside of that room(usually high temperature). This can not happen naturally as heat energy can flow only from high temperature to low temperature.
      To make it happen, external work has to be done on a system to transfer heat from low to high temperature. This work done is mechanical form of energy which is equal to the electrical energy consumed. Hence, mechanical power=electrical power(not considering efficiency of the compressor etc.)
      This electrical power(such as 1875 W) is consumed to pump 5275 W of heat out of a room.
      Net heat dissipated by the system is only the energy consumed in form of electrical energy; but, energy emitted outside the room in an hour = 1875+5275 = 7150 Watt hour by consuming 1875 Watt hour of electrical energy.

  7. In above discussion it is seen that 1.2kwatt electric power can generate 3.516kwatt cooling or mechanical power. But we know that energy (power*time) can not be increased (nor destroyed); can only be converted into another form. Here, is not the conservation of energy rule failed? Will anyone explain more details?

      1. I am sorry but please don’t confuse the actual power rating of the Air conditioner with the converted tonnage in KW, they are absolutely 2 different things. Actual power rating of the AC unit is thee power consumed to run the compressor motor at full load, and the indoor fan too, i.e. total power required to function all the electrical parts of the unit.
        Have you tried connecting a KWH meter to say this 2 TR AC unit?
        If not, I strongly advice you to check by connecting one to understand the actual power consumption,
        Request you not to give such false and misleading information on public blogs.

    1. Because a refrigeration system does indeed NOT create or destroy any energy; it is merely the means of conveyance of heat (or cold as the case may be) from one point to another.
      However, it is good to see recognition of Sir Isaac’s Laws. It does take most engineers a little while, at least, to properly understand the fundamentals of heat transfer and in particular, the behaviour of latent heat flows.

  8. 2 Tonn of refrigeration is equal to 3.51×2 kw in the sense of cooling capacity. But Actually in the sense of electrical engineering when we are considering, the power input for a 2.0 tonn AC will be in the range of 2.6-2.8 kw, Normally taken as 2.8 KW.

    now 25 Kva genset x 0.9 efficiency = 22.5 KVA

    Power consumed by 2.0 Ton ac is 2.8 KW

    Now 22.5/2.8 = 8.03 ~ 8 NOs.

    ie, 8 Numbers of 2.0 Ton AC can loaded by an 25 KVA generator.

      1. How is 1.4 kw Derived for getting the power consumption ? Is it only for the compressor load or also for evaporator fan loads.
        What are the ways to achieve this – technically in terms of compressor selection, fan static pressure considered etc.
        Need this to find the power consumption for a Dx ( Direct expansion) type packaged AC unit, wherein manufacturer claims he cannot meet even 1.6 KW/TR.

  9. we have learnt that 1 Ton = 1400 W = 12000 Btu/h…….then why here posted that 1 TON= 3.516 KW….OR am i wrong …..anywy pls try to justify & make me clear the doubt ….am an electrical engineer …..Is there any problm in just looking the name plate details ,means the max current and confirming the MCB according to that current which were shown on name pate ….rather going for ton ,kw calculations…….please reply to this also

  10. I am mech engg student and interested to know that how much electrical power a refrigerator so that it can run by solar energy using panel

  11. Sir, please explain the difference of actual ac rating and theoretical( 1Ton=3.516KW). this creates confusion. I am working on solar system design. every time I have to check the data sheet of AC. so please…

  12. Unfortunately you are confusing readers, these calculations are wrong in view of power consumption, as the calculations are based on the amount of heat transfer which different from the compressor power consumption, actually I measured the current of 1T AC and it was about 6A and was 12A for the 2 ton AC

    1. u r right
      and also your calculation is @ normal operation, so assume for the 2Ton the starting current equal 16 amp

  13. Sir, I am a electrician,

    Now I Have to take a connection for 4 no of 2 ton carrier split AC. Now how much KWA connection I have to apply?

  14. How is it possible to divide the kVAS with KW and get a simple number . First the KVAS should be converted to KW by multiplying by power factor .

  15. Would like to clarify the explanation above as it is misleading. Tons of refrigeration in terms of watt is different from electrical power input needed in terms of watt to suffice the requirement needed by a room.
    The first is about heating and cooling, mechanical in nature. It is the result of converting electrical energy by a unit, say a motor to run the compressor (mechanical) for heating or cooling. Although heat can be expressed or calculated in various ways, (BTU/hr, calories/s, joules/s, watts and hp), we are only calculating how to condition the temparature of the room. For the electrical power, it pertains to the power input needed by the motor or the HVAC system to achieve the heating needed by a room.
    With that explanation comes the Energy Efficiency Ratio (EER). It is the ratio of cooling provided by a unit (or heating) divided by the amount of electrical input power required to achieve it. On places where there are four seasons, there is what we call Seasonal Energy Efficiency Ratio (SEER). Here in my place, air conditioning units typically only show EER of the equipment as we only have 2 seasons.

    EER = cooling generated by a unit / amount of electrical input to achieve it

    Now for example, a window type air conditioning unit, typically it has an EER of around 9 to 11 bu we may use 10 for illustration. For machines with ACCUs FCUs, chillers etc., this value will go higher as stricter regulations apply to bigger machines for HVAC, because of the point that the higher the EER, the less electricity a person/company pays.
    Going back, if the window type air conditioning unit is rated 1hp and assuming the motor/mechanical system has 85% efficiency, it would require you 877W of electrical power to run it. Applying the EER above, cooling for this unit will yield 8770kJ/hr. In terms of watts of heating and cooling for this specific equipment, it would give you around 2436W. In addition, the recommended cooling area could be up to around 16 square meters. To note, I have computed it in a reverse sense meaning to the point of electrical, though, in reality, you compute first for the heating and cooling requirement of the room before determining the needed machine to achieve it.

  16. An excellent article, thank you. Despite having worked in these fields (process, refrig, powergen etc) for most of my working life, I had forgotten the history as to why refrigeration capacity has customarily, always been measured in tons (short tons too, which is 2000#, not 2240# as per standard imperial ton, nor 2205# for the metric “tonne”).
    Tons as a measure of cold makes so much sense; before reliable mechanical refrigeration came along, things were kept cold with blocks of ice. Where I live, Cambodia, that is still very much the case today. So 2000 pounds of ice, melting at or about the triple point of H²O will provide 1 ton of cooling. Doubtless that was how coolrooms and the like were monitored and measured until the latter part of the 19th century.
    A minor correction: as I recall, CoP is the acronym for “Coefficient of Performance”, as opposed to Coefficient of Power, as, written in the article. And I’m pretty sure that it is usually written big C small o big P, unless you are a hard core acronymer from the US of A (in which case it is probably all upper case).
    cheers // Steve

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