BTU to kW: Conversion Formula, Chart & Examples
Walk into any appliance aisle and you’ll find two air con boxes side by side, one rated in BTU, the other in kilowatts. Both can describe heating or cooling capacity, just using different units. Heaters and portable cooling gear can create the same confusion. Converting between BTU/h and kW makes the ratings easier to compare, but the resulting capacity in kW isn’t the same as the electrical power the appliance draws. This guide explains the conversion and how to tell the two figures apart.
Quick Answer
1 kW of cooling or heating capacity equals roughly 3,412.14 BTU/h.
To convert BTU/h to kW: Divide the BTU/h figure by 3,412.14 (or multiply by 0.000293071).
Example: 12,000 BTU/h ÷ 3,412.14 ≈ 3.52 kW
To convert kW to BTU/h: Multiply the kW figure by 3,412.14.
Example: 2.5 kW × 3,412.14 ≈ 8,530 BTU/h
What Are BTU and kW?
BTU and kW both relate to energy, but appliance specifications use them for different jobs. Once you’ve got that difference straight, the conversion gets easier and the heating and cooling ratings start making sense.
What Is a BTU?
A British Thermal Unit measures energy, and the definition goes back to water. One BTU is the heat it takes to raise a pound of water by one degree Fahrenheit. You’ll rarely see a bare BTU on a box, though. On the box it’s BTU per hour, written BTU/h. That’s the heat a unit can shift into a room, or out of it, in an hour.
What Is a Kilowatt?
A kilowatt is 1,000 watts. A BTU counts energy, and a kilowatt counts how fast it moves. Air con and heat pumps sold here quote capacity in kW, so an installer can read a spec sheet at a glance. Electrical input is quoted in kW as well, while energy use over time is measured in kWh. For a portable power station, compare its AC output with the appliance’s electrical input, not its thermal capacity.
BTU vs. BTU/h
BTU is a quantity of energy. BTU/h is how fast that energy moves, and that’s the one that decides whether you’re comfortable, because a west-facing room takes on heat all afternoon. BTU and BTU/h get used loosely. A unit sold as 12,000 BTU nearly always means 12,000 BTU/h. The per-hour gets quietly left off.
How Do You Convert BTU to kW?
You only need one number to move between the two: divide the BTU/h rating by 3,412.14 and the answer is the thermal capacity in kilowatts.
BTU/h to kW Conversion Formula
kW = BTU/h ÷ 3,412.14
If you’d rather multiply, the same factor inverted gets you there:
kW = BTU/h × 0.000293071
Step-by-Step Conversion Example
Take a 14,000 BTU/h portable, the one that comes out every February:
Start with the rated capacity: 14,000 BTU/h.
Divide 14,000 by 3,412.14.
The result is approximately 4.10 kW of cooling capacity.
How to Convert kW Back to BTU/h
You’ll go the other way just as often. Plenty of imported gear gets sold on its BTU rating. To go back, multiply the kW figure by 3,412.14:
BTU/h = kW × 3,412.14
A 5.0 kW unit, common for open-plan living:
5.0 × 3,412.14 ≈ 17,061 BTU/h
What Are Common BTU/h to kW Conversions?
The ratings below turn up most often on Australian shelves, so you can set an import against a local unit without a calculator.
BTU/h Rating | Thermal Capacity (kW) | Typical Australian Living Context |
5,000 BTU/h | 1.47 kW | A campervan interior, a rooftop tent, or a study nook |
9,000 BTU/h | 2.64 kW | The standard Aussie suburban bedroom, roughly 10–15 m² in a brick-veneer home |
10,000 BTU/h | 2.93 kW | A bedroom, study, or other small room |
12,000 BTU/h | 3.52 kW | A master bedroom with ensuite, or a home office |
15,000 BTU/h | 4.40 kW | A larger bedroom or medium-sized living space |
18,000 BTU/h | 5.28 kW | An open-plan lounge room, or the kitchen and dining space off it |
24,000 BTU/h | 7.03 kW | Large living areas, rooms with a high ceiling, or open living zones |
30,000 BTU/h | 8.79 kW | Larger open-plan areas or multi-room applications |
36,000 BTU/h | 10.55 kW | Multi-room ducted zones, or big open-plan rural rooms |
Where Are BTU and kW Commonly Used?
Which unit you get depends on the product and who built it. Appliances built for the Australian market quote capacity in kW, while imported gear often still carries a BTU/h rating. That’s how both turn up when you search.
Air Conditioners and Heat Pumps
Air conditioners and heat pumps sold here generally list capacity in kilowatts, so local units are easy to compare. BTU/h still turns up on imported systems, on RV air conditioners built for the US market, on marine cooling equipment, and on overseas models.
Heaters and Heating Systems
Heating gear is less consistent, and the unit follows whatever it runs on. Reverse-cycle air conditioners are quoted in kW. Gas heaters and boilers carry their output rating in MJ/h, sometimes with a BTU/h figure alongside.
Portable Cooling and Heating Equipment
Portable air conditioners, window units, caravan air con and diesel heaters are where you’re most likely to run into both units. Caravan gear especially, since much of it comes through importers rather than distributors. Knowing both lets you weigh a local product against an import. When choosing the best camping air conditioner for your setup, also check electrical input, ventilation needs and the space being cooled.
What Should You Consider When Using BTU to kW Conversions?
A BTU-to-kW conversion hands you the heating or cooling capacity, and that’s where it stops. It won’t tell you the power draw. That’s the number you’re after when you size batteries, inverters or portable power systems.
Thermal Capacity vs. Electrical Power Consumption
Converting BTU/h to kW gives you thermal capacity, not electrical power consumption.
A 12,000 BTU/h air conditioner shifts about 3.52 kW of cooling capacity, but that doesn’t mean it’s drawing 3.52 kW out of the power point. The actual draw is a smaller number, and it shifts with the machine, the conditions and how hard the compressor’s working.
For portable cooling, camping, or shorter home backup needs, the EcoFlow DELTA 3 Max Plus Portable Power Station offers 2,048Wh of capacity and 3,000W of rated AC output. Its higher surge capacity also makes it suitable for appliances with brief startup loads, while expandable storage gives you more flexibility if longer runtime is needed.
For larger air conditioners, heavier household loads, or longer backup periods, the EcoFlow DELTA 3 Ultra Plus Portable Power Station provides 3,072Wh of capacity and 3,600W of rated AC output, with a 7,200W surge rating. Its larger base battery and higher output make it better suited to more demanding backup setups.
Whichever way you go, size the power station to the air conditioner’s rated electrical input rather than the thermal kW you worked out, and check the startup power requirement before you plug in. That second number’s what catches people out when the compressor kicks back in and asks for more than it did a minute earlier.
Efficiency and Real-World Energy Use
What you pay for comes down to the machine’s efficiency, the temperature outside, room size, the insulation and how hard the compressor works. A scorcher of an afternoon pushes the number up. So do a bare ceiling, unshaded glass and gaps under doors. Deciding what temperature to set your air conditioner in summer is another practical part of managing energy use.
So treat the converted thermal capacity as a way to compare output. For running cost, look at the rated input power and the efficiency figures.
Conclusion
Divide the BTU/h rating by 3,412.14, and you’ve got the number a local spec sheet would have handed you. A 12,000 BTU/h air conditioner puts out roughly 3.52 kW of cooling. That figure is heat moved, not electricity drawn. Anything you size to run it, whether that’s a circuit, an inverter, a battery or a portable power station, starts from the appliance’s rated electrical input, plus whatever the compressor asks for the moment it restarts.
FAQ
How much does it cost to run a 10,000 BTU AC for 24 hours?
A 10,000 BTU portable puts out roughly 2.93 kW of cooling, and running one flat out for 24 hours costs you about $7.50 to $9.20. That’s a draw of 900W to 1,100W, at the average Australian residential rate of $0.35 per kWh. Actual daily cost may be lower because inverter air conditioners can reduce compressor output once the room approaches the set temperature.
How many kW are in 15,000 BTUs?
There are roughly 4.40 kW of thermal capacity in a 15,000 BTU appliance (15,000 BTU/h if you’re being strict, though the box will leave the per-hour off). That’s 15,000 divided by 3,412.14.
Is 18,000 BTU enough for a living room?
An 18,000 BTU/h unit provides about 5.28 kW of cooling and may suit some living rooms, but floor area alone cannot confirm the right size. High ceilings, afternoon sun, insulation and local climate affect the cooling load. Use a room-sizing assessment or ask a qualified installer rather than assuming a 6.0 or 7.0 kW unit is required.
Does a higher BTU rating mean higher electricity use?
Not necessarily, and it’s the assumption that sends people home with the wrong machine. Consumption depends on the cooling load, efficiency, settings and running hours, not the headline rating alone. A correctly sized inverter unit can reduce its output as demand falls. An undersized unit may struggle to maintain the set temperature, but a larger unit is not automatically cheaper to run.
What happens if an air conditioner is oversized for a room?
An air conditioner with too much capacity for the room may cool the space quickly and cycle off before removing enough moisture, leading to uneven temperatures and poor humidity control. Frequent short cycling can also reduce efficiency and increase compressor wear, although inverter models can reduce output and are less prone to this problem. For heating equipment, oversizing can also cause frequent cycling and uneven comfort, but humidity control is mainly a concern in cooling mode.