AC Ton to BTU and kW: 1, 1.5 and 2 Ton Explained

The short answer

In air conditioning, 1 ton means a cooling capacity of 12,000 BTU per hour, which equals about 3.517 kW of cooling. So a 1.5 ton AC is rated for about 18,000 BTU/h or 5.28 kW, and a 2 ton AC for about 24,000 BTU/h or 7.03 kW. You can check any BTU figure with the Energy Converter by converting BTU to watt-hours (Wh): the BTU per hour figure converts to the same number of watts. The cooling kW is not the electricity the AC uses; that is much lower and depends on the unit's efficiency.

What "ton" means for an AC

The ton here is not a weight. It is the ton of refrigeration, a unit of cooling power. It was originally defined as the rate of heat removal needed to freeze or melt one short ton (2,000 lb) of ice at 0 °C in 24 hours. Today it is defined as exactly 12,000 BTU per hour (using the International Table BTU), which is about 3.516853 kW.

So when a shop calls an AC "1.5 ton", it means the unit is rated to remove about 18,000 BTU of heat from the room every hour.

AC tonnage conversion table

AC size	Cooling in BTU per hour	Cooling in kW
0.75 ton	9,000	2.64
1 ton	12,000	3.52
1.5 ton	18,000	5.28
2 ton	24,000	7.03
3 ton	36,000	10.55

The kW values use 1 BTU = 1,055.06 joules, the same value the Energy Converter uses.

Formulas

• BTU per hour = tons × 12,000
• kW = BTU per hour × 0.000293 (or BTU per hour ÷ 3,412)
• kW = tons × 3.517
• tons = kW ÷ 3.517

Worked example: 1.5 ton

1.5 × 12,000 = 18,000 BTU/h

18,000 × 0.00029307 = 5.275 kW

Rounded: about 5.28 kW of cooling

Worked example: a label that says 5.0 kW

5.0 ÷ 3.517 = 1.42 ton. Labels and brochures often round, so a unit sold as 1.5 ton may list a measured capacity a little below or above 5.28 kW.

How to do it with the Energy Converter

BTU is an energy unit and BTU per hour is a power unit, so it helps to think of "one hour's worth". If an AC removes 12,000 BTU in one hour, that is the same as removing 3,517 Wh in one hour, which is a rate of 3,517 W or 3.517 kW.

Open the Energy Converter.

Type the BTU per hour figure, for example 18000, in Value to convert.

Set From to BTU.

Set the target to Watt-hour (Wh). The result for 18,000 is 5,275.3 Wh, so the cooling rate is about 5,275 W, or 5.28 kW.

If you choose Kilowatt-hour (kWh) instead, you read 5.2753 directly, which is the kW figure.

To go the other way, set From to kWh, type 1, and read 3,412.13 BTU. That is where the "divide by 3,412" shortcut comes from.

Cooling capacity is not power consumption

This is the most common misunderstanding. A 1.5 ton AC with 5.28 kW of cooling does not use 5.28 kW of electricity. An air conditioner moves heat from inside to outside; it does not create the cooling from electricity one-for-one. The ratio between cooling output and electrical input is the efficiency figure, shown on labels as EER, ISEER, SEER or COP depending on the country.

As an illustration only: if a unit delivers 5,275 W of cooling at an efficiency ratio of 3.5 (watts of cooling per watt of electricity), its electrical input at that moment is 5,275 ÷ 3.5 ≈ 1,507 W, or about 1.5 kW. Real consumption varies with the outside temperature, the thermostat setting, whether it is an inverter model and how long the compressor runs. For the actual input power, check the rating label or the manufacturer's specification sheet.

Once you have the input wattage and the hours of use, you can estimate electricity units. See How to Calculate Electricity Units: Watts to kWh.

Reading AC specifications

• Cooling capacity may be listed in W, kW, BTU/h or tons. They all describe the same thing.
• Rated input power (in W) is the electricity drawn under test conditions.
• Efficiency (EER, ISEER, SEER or COP) is cooling divided by input. Higher is better.
• Some brochures list capacity at more than one test condition, for example rated and maximum. Compare like with like.

Common mistakes

• Treating ton as weight. It has nothing to do with how heavy the unit is.
• Mixing BTU and BTU/h. BTU is energy; BTU/h is a rate. AC sizes always mean BTU per hour, even when "per hour" is left out.
• Using cooling kW for the electricity bill. Use the input power instead.
• Comparing kW figures from different test conditions. A capacity measured at a lower outdoor temperature can look higher.

Quick answers

• 1 ton = 12,000 BTU/h = 3.517 kW
• 1.5 ton = 18,000 BTU/h = 5.275 kW
• 2 ton = 24,000 BTU/h = 7.034 kW
• 1 kW = 3,412 BTU/h = 0.284 ton

For more on energy units, the converter also handles kJ, kcal and electron volts; see kJ to kcal: How to Read Calories on a Food Label for a different everyday use.