🔁Convert BTU per hour to kilowatts and tons

✓ Tested & verified Updated: Aug 8, 2026 How we calculate this

BTU · kW · tons converter

Amount

Given in

12,000 BTU/h ≈ 3.5 kW

= 1 tons of refrigeration · 3,517 watts of heat

Common size	BTU/h	kW	Tons
Room / window	5,000	1.5	0.4
Room / window	8,000	2.3	0.7
Room / window	9,000	2.6	0.8
Room / window	12,000	3.5	1
Mini-split	18,000	5.3	1.5
Mini-split	24,000	7	2
Central	36,000	10.6	3
Central	48,000	14.1	4

One ton is exactly 12,000 BTU/h; one kilowatt is 3,412.14 BTU/h. Both are exact by definition, so converting out and back returns the number you started with.

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How do you convert BTU to kW and tons?

Divide BTU per hour by 3,412.14 for kilowatts, or by 12,000 for tons. So 12,000 BTU/h is 3.52 kW and exactly 1 ton; 24,000 BTU/h is 7.03 kW and 2 tons; 9,000 BTU/h is 2.64 kW and 0.75 tons.

All three describe the same thing — a rate at which heat is moved — and which one you meet depends entirely on the catalogue. US room air conditioners are labelled in BTU per hour. Central systems are quoted in tons. Everywhere outside the United States, and for every heat pump specification sheet in Europe, the unit is kilowatts.

The ton is the strange one. It comes from the ice trade: one ton of refrigeration is the cooling produced by a ton of ice melting over 24 hours, which works out at 12,000 BTU per hour. It has nothing to do with what the equipment weighs, which is a very common assumption and occasionally an expensive one.

Equipment sizes cluster around a handful of values, and it is worth being able to recognise them in any of the three units.

BTU/h	kW	Tons	Usually seen as
5,000	1.47	0.42	smallest window unit
9,000	2.64	0.75	smallest mini-split head
12,000	3.52	1.0	one-ton unit, common split
18,000	5.28	1.5	large room, small house
24,000	7.03	2.0	two-ton central system
36,000	10.55	3.0	three-ton central system
60,000	17.58	5.0	largest common residential

A useful mental shortcut: BTU ÷ 3,400 ≈ kW, and BTU ÷ 12,000 = tons exactly. That gets you close enough to spot when a quote has been converted wrongly, which happens more often than it should.

Frequently asked questions

How many kW is 12,000 BTU?

3.52 kW of cooling. That is a one-ton unit, the most common mini-split head size, and the same machine will be advertised as 12,000 BTU in the United States and 3.5 kW in most of the rest of the world. The small discrepancy between 3.52 and the marketed 3.5 is rounding, not a different machine.

Is a ton of air conditioning about weight?

No. It is a unit of cooling rate inherited from the ice business — the rate at which one ton of ice absorbs heat as it melts over a day. A three-ton condenser weighs a couple of hundred pounds, not three tons, though it is heavy enough that the confusion rarely causes real problems beyond conversation.

Do heating and cooling use the same conversion?

Yes for BTU and kilowatts, which are just units of power. Tons are only used for cooling by convention — you will not see a furnace quoted in tons — but the arithmetic would work identically if anybody did.

What is the difference between kW of output and kW of electricity?

Everything, for a heat pump. A heat pump rated at 3.5 kW of heating output might draw only 1 kW of electricity to produce it, because it moves heat rather than making it — that ratio is the COP. For an electric resistance heater the two are the same number, which is why resistance heat is the expensive option.

Why do some listings show two BTU figures?

Usually a portable air conditioner showing both the current SACC rating and the older ASHRAE one, which differ by 30 to 40% for the same machine. Occasionally it is a heat pump showing cooling and heating capacity, which genuinely are different numbers. Check the label before assuming the bigger figure is the real one.

How many BTU is one watt?

3.412 BTU per hour. So a 1,500 W space heater is 5,118 BTU/h, and a 2 kW panel heater is 6,824 BTU/h. This is the conversion that lets you compare an electric heater with a gas one — and the one behind the 10 watts per square foot rule of thumb for electric heating.

How we calculate this

Conversions use exact definitions: 1 ton of refrigeration = 12,000 BTU per hour, and 1 kilowatt = 3,412.142 BTU per hour (derived from 1 BTU_IT = 1,055.05585262 joules). Watts convert at 1/1000 of the kilowatt figure. Because the constants are exact, converting a value out to another unit and back returns the original number rather than accumulating rounding error. Displayed values are rounded for readability only — the calculation itself carries full precision. The size chart lists nominal capacities as marketed rather than measured performance, which varies with outdoor temperature for every heat pump.

Worked example

With Amount 12000, Given in BTU per hour, this page works out 12,000 BTU/h ≈ 3.5 kW. = 1 tons of refrigeration · 3,517 watts of heat

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