Aircon HP to Watts Calculator
How much electricity a 1 HP, 1.5 HP or 2 HP air conditioner actually draws — plus monthly kWh and running cost. Aircon "HP" is a cooling class, not shaft power, so 746 W per HP doesn't apply.
Ask how many watts a 1 HP aircon uses and you'll get two very different answers. One camp multiplies by 746 and says 746 W. The other quotes 900 W from a rating plate. Only the second is meaningful — and understanding why is the difference between a sensible electricity budget and a wildly wrong one.
Why 1 HP of Aircon Is Not 746 Watts
In Southeast and East Asia — the Philippines, Malaysia, Indonesia, Hong Kong, Singapore — air conditioners are sold by horsepower class. "1.5 HP split type" is a size on a showroom tag, in the same way a shirt is a size medium.
That label descends from the compressor motors used in early units, but it stopped tracking motor power decades ago. Today it is a cooling capacity class, anchored roughly at 1 HP = 9,000 BTU/h. Applying the mechanical conversion of 746 W per horsepower to it produces a number with no physical meaning.
| Quantity | 1 HP aircon | What it describes |
|---|---|---|
| Cooling capacity | ≈ 9,000 BTU/h = 2.64 kW | Heat moved out of the room |
| Electrical input | ≈ 900 W = 0.9 kW | What the meter records |
| "746 W per HP" | — not applicable | Mechanical shaft power, a different quantity |
Notice that the cooling output is about three times the electrical input. That isn't a violation of anything — an air conditioner is a heat pump, not a heater. It moves existing heat rather than creating it, so the ratio of heat moved to electricity consumed is comfortably above one. That ratio is exactly what EER measures.
EER is BTU/h per watt at a fixed test condition; CSPF is the seasonal average used across Southeast Asia
Aircon HP to Watts Table
Full-load electrical input at three efficiency levels. Use the low-efficiency column for older window and non-inverter units, and the high column for a modern high-CSPF inverter.
| HP class | Cooling BTU/h | EER 8.5 (older) | EER 10 (typical) | EER 13 (high-eff. inverter) |
|---|---|---|---|---|
| 0.5 HP | 5,000 | 588 W | 500 W | 385 W |
| 0.75 HP | 7,000 | 824 W | 700 W | 538 W |
| 1 HP | 9,000 | 1,059 W | 900 W | 692 W |
| 1.5 HP | 12,000 | 1,412 W | 1,200 W | 923 W |
| 2 HP | 18,000 | 2,118 W | 1,800 W | 1,385 W |
| 2.5 HP | 24,000 | 2,824 W | 2,400 W | 1,846 W |
| 3 HP | 30,000 | 3,529 W | 3,000 W | 2,308 W |
| 4 HP | 36,000 | 4,235 W | 3,600 W | 2,769 W |
| 5.5 HP | 48,000 | 5,647 W | 4,800 W | 3,692 W |
| 6.5 HP | 60,000 | 7,059 W | 6,000 W | 4,615 W |
The HP ladder is not linear — and that surprises people
Look at the middle column of the table. 1 HP is 9,000 BTU/h but 1.5 HP is 12,000, not 13,500. 2 HP is 18,000, not 18,000-by-arithmetic-from-1-HP. The ladder follows the standard capacity steps manufacturers actually build — 5,000, 7,000, 9,000, 12,000, 18,000, 24,000 — with HP labels attached afterwards.
Practical consequence: going from 1 HP to 1.5 HP buys you 33% more cooling, but 1.5 HP to 2 HP buys 50% more. The step sizes are uneven, so "one size up" means different things at different points. Our aircon HP room size calculator works out which step you actually need.
Inverter vs Non-Inverter: Where the Saving Really Comes From
A widespread misreading is that an inverter unit draws fewer watts. At full load it draws about the same as a comparable fixed-speed machine of the same capacity. The saving is structural, not instantaneous.
- Non-inverter: the compressor is either on at 100% or off. Once the room is cool it cycles — full power, off, full power, off. Each restart carries an inrush penalty and a period of poor efficiency.
- Inverter: the compressor slows to match the heat leaking into the room, often running at 30–50% output indefinitely. No cycling, no restart losses, and a compressor is measurably more efficient at part speed.
Across a cooling season that generally lands at 30–50% lower consumption for the same comfort. It also means the nameplate wattage overstates what an inverter really averages — a realistic day is often 50–70% of rated input. Full comparison in inverter vs non-inverter aircon.
Read Your Own Rating Plate — It Beats Any Estimate
Everything above is a model. The actual tested figure for your unit is printed on it. Look on the side of the indoor unit or on the outdoor condenser for:
- Rated power input (W) — the number you want, straight off the plate
- Rated current (A) — multiply by your supply voltage for an input estimate; a 4.1 A unit on 230 V is roughly 940 W
- Cooling capacity (kW or BTU/h) — the honest capacity, which may not match the HP badge
- EER / CSPF / ISEER — the efficiency figure used in your market's energy label
If the plate and the showroom badge disagree, believe the plate. Marketing HP labels are approximate; rating plates come from a test procedure.
Working Out What It Costs You
Three steps, and one honest caveat:
- Input kW = BTU/h ÷ EER ÷ 1,000
- Daily kWh = input kW × hours the compressor runs
- Cost = daily kWh × your tariff × days
The caveat is step 2. "Hours the aircon is switched on" and "hours the compressor is running at rated power" aren't the same thing. A non-inverter cycling on a mild night may only compress for a third of the time; an inverter modulates rather than stopping. Treat the calculator's figure as a ceiling and expect real bills below it. For energy accounting in horsepower terms, see HP to kWh.
Related Tools
For capacity conversions rather than consumption, use BTU to HP, ton to HP and the aircon conversion chart. To size a unit for a room see aircon HP by room size, and to identify what you already own, how to check aircon horsepower.
Frequently Asked Questions
Roughly 750–1,100 W. It delivers about 9,000 BTU/h, so at EER 10 that's 900 W. Older non-inverters sit high in the range, efficient inverters low.
No — and this is the key point. Aircon HP is a cooling class, not shaft power. A 1 HP unit moves ~2.64 kW of heat while drawing ~0.9 kW of electricity.
About 1,000–1,450 W. Rated near 12,000 BTU/h, so at EER 10 that's roughly 1,200 W.
1.5–2.1 kWh per hour of full-load compressor running. At 18,000 BTU/h and EER 10 that's about 1.8 kW.
Not at full load — similar. The saving is at part load, where the compressor slows instead of cycling. Seasonally that's typically 30–50% less energy.
Input kW × compressor hours × tariff. Because an inverter rarely runs flat out, budget 50–70% of the nameplate figure for a realistic day.
The rating plate on the indoor or outdoor unit. Look for rated power input (W), or multiply rated current by supply voltage. That tested figure beats any HP-based estimate.
No. An undersized unit runs flat out and never reaches setpoint. A right-sized larger unit reaches setpoint then modulates. Severe oversizing is also wasteful — short cycling stops the coil dehumidifying.