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When shopping for an air conditioner, manufacturers often list the motor’s power in either kilowatts (kW) or horsepower (hp). Although these figures reflect the motor’s electrical output, they do not directly indicate the unit’s cooling performance. Nonetheless, knowing how to convert between the two units can help you compare specifications across brands.
1 horsepower equals 0.7457 kilowatts, and conversely, 1 kilowatt equals 1.337 horsepower. These constants stem from the relationship between mechanical work and electrical energy: 1 hp = 745.7 watts.
James Watt introduced the term “horsepower” in the 18th century to quantify the output of steam engines. In physics, power is the rate of work performed. A watt—named after Watt as well—is the electrical counterpart: 1 watt is the power delivered when 1 ampere flows through a 1‑volt potential. This equivalence allows the simple conversion between horsepower and watts, and therefore between horsepower and kilowatts.
An air conditioner’s condenser motor compresses refrigerant, which then travels through coils where it evaporates and absorbs heat. While the motor’s power affects how quickly refrigerant circulates, the actual cooling capacity depends on refrigerant type, coil size, and system design. For this reason, the industry prefers the British Thermal Unit (BTU) as the standard measure of cooling power—1 BTU equals the energy needed to raise 1 lb of water by 1 °F.
If a unit is rated at 1.5 hp, its motor power is:
1.5 hp × 0.7457 kW/hp ≈ 1.12 kW.
Conversely, a 3.5 kW motor produces:
3.5 kW × 1.337 hp/kW ≈ 4.68 hp.
These conversions help you match motor ratings when browsing international product listings, but remember that BTU figures remain the most reliable indicator of an air conditioner’s true cooling performance.
