Australian, European and many Asian spec sheets rate air conditioners by cooling kilowatts, while shops in Southeast Asia sell the same units by horsepower. This converter bridges the two — using the cooling capacity, not the electrical draw.
Cooling kW to HP Formula
Critical distinction: the kW on a capacity label is cooling output; the kW on the energy label is electrical input, typically 2.5–4× smaller. A "2.5 kW cooling / 0.78 kW input" unit is one machine described two ways. Never size a room by the input figure, and never size a generator by the cooling figure. This is a different question from converting mechanical power — for that see kW to HP.
Cooling kW ↔ Aircon HP ↔ BTU ↔ Tons
| Cooling kW | Aircon HP | BTU/hr | Tons |
|---|---|---|---|
| 2.0 | 0.76 | 6,824 | 0.57 |
| 2.5 | 0.95 | 8,530 | 0.71 |
| 3.5 | 1.33 | 11,942 | 1.00 |
| 5.0 | 1.90 | 17,060 | 1.42 |
| 7.1 | 2.69 | 24,225 | 2.02 |
| 9.0 | 3.41 | 30,708 | 2.56 |
Worked Example
The Two Kilowatt Figures on Every Spec Sheet
This is the single most expensive misreading in air conditioner shopping. Modern spec sheets carry two kilowatt numbers, and they describe opposite ends of the same machine.
| Label on the sheet | What it is | Typical value on a 1 HP unit | Use it for |
|---|---|---|---|
| Cooling capacity (kW) | Heat removed from the room | 2.64 kW | Sizing the unit to the room. This is the figure this calculator converts. |
| Power input (kW) | Electricity drawn from the wall | 0.7–1.1 kW | Running cost, breaker sizing, generator sizing, solar planning. |
The ratio between them is the efficiency rating — roughly 2.5 to 4 times, because an air conditioner moves heat rather than creating it. Two consequences worth internalising:
- Sizing a room from the input figure massively undersizes the unit. A "0.78 kW" label is not a 0.3 HP aircon; it is a 1 HP aircon drawing 780 watts.
- Sizing a generator from the cooling figure massively oversizes it. You need the input kW, plus headroom for compressor startup surge.
For the electrical side specifically, use aircon HP to watts, which works from efficiency rating to input power and running cost.
What Room Size Each Cooling kW Suits
A practical starting point for a standard residential room with normal ceiling height, moderate insulation and one external wall.
| Cooling kW | Aircon HP | Typical room area | Example space |
|---|---|---|---|
| 2.0 | 0.75 HP | 10–14 m² | Small bedroom, study |
| 2.5 | 1 HP | 14–20 m² | Standard bedroom |
| 3.5 | 1.5 HP | 20–30 m² | Master bedroom, small lounge |
| 5.0 | 2 HP | 30–40 m² | Living room |
| 7.1 | 2.5 HP | 40–55 m² | Open-plan living/dining |
| 9.0 | 3 HP | 55–70 m² | Large open plan, small office |
Push toward the larger size if the room faces afternoon sun, has floor-to-ceiling glazing, a high or vaulted ceiling, poor insulation, a kitchen in the same space, or more than two or three regular occupants. Full sizing method in the aircon HP by room size calculator.
Reading Inverter Capacity Ranges
Inverter units rarely list a single capacity. Expect something like:
Convert the rated middle figure, not the maximum. The rated value is what the unit sustains at standard test conditions and what the HP badge is derived from — 3.5 kW rated is a 1.5 HP unit, even though it can briefly push to 4.2 kW when pulling a hot room down. Sizing on the 4.2 figure buys a unit that spends its life short-cycling.
The minimum figure matters too, and it is the real advantage of an inverter: a unit that can throttle down to 1.0 kW will hold a cool room steadily instead of switching on and off. See inverter vs non-inverter.
Which Market Uses Which Unit
| Unit on the label | Where you'll see it | Convert with |
|---|---|---|
| Cooling kW | Australia, New Zealand, Europe, UK | This page |
| Horsepower (HP) | Philippines, Malaysia, Indonesia, Hong Kong | This page, or the full chart |
| BTU/hr | United States, Middle East | BTU to HP |
| Tons / TR | India, US commercial, Middle East | Ton to HP |
| Tonner | Philippines (commercial) | Tonner to HP |
| HP (VRF/VRV) | Commercial systems worldwide | VRF HP to TR — a different HP scale at 2.8 kW |
That last row catches out even HVAC professionals: commercial VRF outdoor units use horsepower at roughly 2.8 kW per HP, not the residential 2.64 kW. A 10 HP VRF unit is about 6% larger than ten residential horsepower would suggest.
Frequently Asked Questions
About 0.95 HP — it's what SE Asian markets sell as a "1 HP" unit.
No. Mechanical kW→HP divides by 0.7457; cooling kW→aircon HP divides by 2.638, because aircon "HP" is a capacity label, not mechanical power. Mixing them up gives answers ~3.5× wrong.
The "cooling capacity" or "rated capacity" kW. The "power input" kW is electricity consumption — use that only for running-cost and generator sizing.
About 3.5 kW of cooling — 12,000 BTU/hr, or 1 ton. Its electrical input will be closer to 1.0–1.4 kW depending on efficiency.
The rated middle figure — 3.5 kW, so a 1.5 HP unit. The bracketed numbers are the minimum and maximum the variable-speed compressor modulates between. Sizing on the 4.2 maximum buys a unit that short-cycles.
Roughly 30–40 m² for a standard room — a typical living room. Go a size larger for afternoon sun, large glazing, high ceilings or an open kitchen.
No. An oversized unit reaches setpoint fast, shuts off, and never runs long enough to dehumidify — leaving the room cold and clammy, with higher bills from short-cycling.
No. VRF and VRV outdoor units use a different horsepower scale of about 2.8 kW per HP rather than 2.64. Use the VRF HP to TR converter instead.