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Why AC Rated in Tons, Not in kW or kVA?

Why Air Conditioner and Refrigerator Rated in Tons

If you pick this article, You will be able understand;

  • Why AC rated in Tons, Not in kW or kVA?
  • Definition of Ton
  • How many kW and HP are there in 1 Ton?
  • How to convert Ton to kW and vice versa?
  • How much Current in Ampere will a 2 Tons AC draws in Single Phase & Three Phase System?
  • How many 2 Ton A.C (Air conditioner) can I run on a 25 kVA Generator?
  • What is the suitable rating of MCB for 2 Ton and 1 Ton AC (Air conditioner) and why?
  • and much more…

Why AC rated in Tons, Not in kW?

Refrigeration and air-conditioned (AC) systems are always rated in Tons. Air conditioners are rated in Tons capacity instead of kW or kVA rating because Air conditioners are designed on the basis of quantity of heat removal from room, hall or specific area. Quantity of heat is termed in Tons means if an air conditioner is able to remove 1000 kilo calories of heat or 4120 kilo joules or 12000 BTU of heat in an hour that AC rated as 1 Ton of AC because 1000 kilo calories or 4120 kilo joules or 12000 BTU equal to one Ton of heat. Also, this is the same case for freezer and refrigerator i.e. refrigeration system.Why AC Rated in Tons, Not in kW or kVA

Good to know:

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.

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 equipments. 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.

How many kW and HP are there in 1 Ton?

1 Ton = 3.5168525 kW = 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 = 4.714 Hp

How to convert Ton to kW and vice versa?

One RT(Refrigeration Ton) = 3.5168528 kW…

1 R= 3.5168528 kW

1 kW = 0.284345 RT(Refrigeration Ton)

1 kW = 0.28434517 RT


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

P(kW) = P(RT) × 3.5168528


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


P(kW) = 3 RT × 3.5168528

P(kW) = 10.55 kW

3 Ton AC = 10.55 kW

How much Current in Ampere will a 2 Tons AC draw in Single Phase & Three Phase System?

Suppose, There are 230V and Power factor = Cosθ = 0.95 in Single Phase AC system

1 Ton = 3,516.8528 Watts = 3.516 kW.

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

Power in a Single Phase AC System

P = VxI Cosθ and current…

I = P / (V x Cosθ)….. Where Cosθ = Power factor

I = 7032W / (230V x .95)

I = 32.18 A

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

And in Three Phase System

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

Power in a Three Phase AC System

P =√3 x VLxIL Cosθ and current….

I = P /( √3xVxCosθ)

I = 7032W / (1.732 x 440V x .85) Where Cosθ = Power factor and √3 = 1.732

I = 10.855 A

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

Good to Know:

This is just calculation based on Electrical formulas. In real, 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.. 
If this is a 230 volt system, then air conditioner load current would be = 4000/(230x.95) = 18.5 A

For More detail…Check the Air conditioner Name plate rating.

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.

How many 2 Ton A.C (Air conditioner) can I run on a 25 kVA Generator

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

The Efficiency of Utility Power Generator is 90% approximately.

Efficiency of Generator = 25kVA x (90/100) = 22.5kVA

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

22.5kVA / 7032W = 3

So you can run Three Air conditioners of 2 Tons each on a 25kVA Generator.

What is the suitable rating of MCB for 2 Ton and 1 Ton AC (Air conditioner) and why?

As we have calculated the load current for 2 Ton AC Air conditioner…

Calculated Current for 2 Ton A.C = I = 32.18 A

Now 40A Class “C” MCB (miniature circuit breaker) would be suitable for 2 Ton AC (air-condition) because in starting time it takes more current of the full load current

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

Good to Know:

Class “’C’ Type MCBs

Class “C” Type MCBs are suitable for installations with high inrush of current at the starting switching time. in other words, equipment and devices having 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
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  1. Junaid Khan says:

    why we take power factor 0.95 in single phase while in 3 phase we take it 0.85..???

    1. Electrical Technology says:

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

    2. Junaid Khan says:

      thanks for your precious time… :-)

    3. Electrical Technology says:

      Most welcome…And Thanks for Your appreciation …

    4. Anonymous says:

      @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

    5. Anonymous says:

      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. mohammad khurram says:

        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 !

      2. M.M. Alam says:

        Yes, u r correct. I found in Samsung AC, the rating for 1 Ton(12000 BTU) AC is 1200 Watts.

      3. Nilesh Darekar says:

        Yes, You r correct.

    6. due to the variation in phase current

  2. VIKRAM MISHRA says:

    i have seen some company r introducing their AC which consume power less than a Hair Dryer..<br />How??

    1. Electrical Technology says:

      For example…???

  3. Anonymous says:

    Great piece of Information!

  4. lg split air conditioner says:

    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. anonymous says:

      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?

  5. Anonymous says:

    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. Anonymous says:

      here comes the role of ,EER ,energy efficiency rating<br />

    2. 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

  6. Adeel Watto says:

    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

  7. Anonymous says:

    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

  8. Anonymous says:

    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.

    1. Masood.Jilani says:

      I am thankful of confirming about difference b/w electrical and mechanical watts

      1. Masood.Jilani says:

        I want to be in contact of this valuable page ho

  9. 1 ton=3.5kw…in this 3.5kw is electrical power or its like cooling capacity unit…please any one explain me

  10. 1 ton=3.5kw…in this 3.5kw is electrical power or its like cooling capacity unit…please any one explain me

    1. Engr.Azmat khan says:

      it is rated power in kilo watt to be consmed.

  11. Lal Kumara says:

    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.

  12. sirajafridi says:

    dear sir explain me ac and dc difference and also dc motor tarq and ac motor tarq

  13. 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. Electrical Technology says:

      1 Ton = 3.5168525 kW = 4.714Hp = 3,516.8528 Watts = 3.516 kW.
      Where is 1.2kW in the above discussion ????

      1. K G BALAJI says:

        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.

    2. JS Broadbent says:

      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.

  14. carlo villarta says:

    Haha nice thankyou xo much .. electrical technology

  15. anonymous says:

    See name plate and clarify the above issue

  16. 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.

  17. mohammad ajazuddin says:

    i need how many kw of 174 ton air conditioner

    1. 174 x 1.4KW = 243.6 KW Power consumption

      174 x 3.51 KW = 610.7 KW Cooling Capacity

      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.

  18. Jayakumar v says:


    I want to know the details about chiller & its operation.

  19. vipin mathews says:

    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

  20. Thejaswini says:

    Very usefull website.. Very much informative

  21. R.S.GOUDA says:

    very useful website learned many more things regarding A.C

  22. anjum chodhary says:

    very informatve site

  23. Can i get all info available on panel board

  24. 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

  25. SASHI ALORA says:

    very informative and helpful

  26. 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…

  27. Sir, our 150Kva generator how many 1.5 ton A/C can work?

  28. How much electricity produced by A 125kv genset? How much ton of acs can we run on 125kv genset?

  29. 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

  30. why dont we use kilowatt can u plz elaborately explain it sir..I couldnot understand it properly..

  31. electricguru says:

    1 .2 KW is electrical power required for 1 TR to operate . 3.5 kw is cooling capacity of 1TR ac .

  32. 9000 btu = 1hp (industrial convertion for cooling capacity)? Please explain

  33. Anil Cyriac says:

    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?

  34. Anonymous says:

    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 .

  35. how Resistance of a 3 phase moter can be calculated if its power and Volt is known.

  36. Roy Juguilon says:

    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.

  37. Anastasia Gordon says:

    Thank you for nice explanation.

  38. JS Broadbent says:

    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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