Power Converter
Convert between watts, kilowatts, horsepower and BTU/hr.
Kilowatt (kW)
111.855
from 150 Horsepower (hp)
Watt (W)
111,855
Horsepower (hp)
150
BTU/hour
381,665.193759
Megawatt (MW)
0.111855
AI Breakdown & Smart Takeaway
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How the Power Converter works
The GKCalculators Power Converter instantly converts between watts, kilowatts, horsepower, and BTU/hr — the four units you'll encounter most often when comparing motors, HVAC systems, generators, and electrical equipment. Whether you're an engineer sizing a motor, a homeowner evaluating an air conditioner, or a student working through a physics problem, this tool gives you fast, accurate cross-unit results without manual calculation.
Power is a measure of energy transferred or work done per unit of time. The challenge is that different industries have adopted different preferred units: electrical engineers work in watts and kilowatts, mechanical engineers and automotive professionals favor horsepower, and HVAC and heating specialists use BTU per hour. None of these units are inherently better — they simply evolved within their own fields. A power converter bridges these worlds by applying fixed, internationally recognized conversion factors to translate any input value into all other supported units simultaneously.
The conversion factors are exact constants derived from fundamental physical definitions. One mechanical horsepower is defined as exactly 745.69987 watts, a figure rooted in 18th-century measurements of draft horse output by James Watt. One BTU per hour equals approximately 0.29307 watts, where the BTU (British Thermal Unit) itself is defined as the energy needed to raise one pound of water by one degree Fahrenheit. Kilowatts are simply watts scaled by 1,000, making the kW-to-watt conversion the most straightforward of the group. Because these factors are constants, the converter produces exact results for any input — there is no estimation involved.
A common source of confusion is that 'horsepower' is not a single unit — there are at least three variants in practical use. Mechanical (or imperial) horsepower is the most common in the US for motors and engines (745.7 W). Metric horsepower, used widely in Europe and on vehicle datasheets outside North America, equals 735.499 W. Electrical horsepower, used specifically for electric motor ratings, is exactly 746 W. The differences are small but matter in precision engineering contexts. This converter uses mechanical horsepower as the default, which is the standard in most US engineering and consumer applications.
A mistake users often make is confusing power with energy. Power (watts, horsepower, BTU/hr) is a rate — it tells you how fast energy is being used or produced at any given moment. Energy (watt-hours, kilowatt-hours, BTUs) is the total amount consumed over time. When you convert 5 kW to BTU/hr, you're converting a rate to another rate, not calculating how much total energy will be used. This distinction matters enormously for electricity bills, generator fuel consumption, and HVAC load calculations, where you need both the power rating and the duration of operation.
Formula
1 Mechanical HP = 745.69987 W | 1 kW = 1,000 W | 1 BTU/hr = 0.293071 W Conversions: HP → W: multiply by 745.69987 kW → W: multiply by 1,000 BTU/hr → W: multiply by 0.293071 W → HP: divide by 745.69987 W → kW: divide by 1,000 W → BTU/hr: divide by 0.293071
Pro tips
- When comparing air conditioner or heat pump specs, convert everything to BTU/hr first — a 3-ton AC unit produces 36,000 BTU/hr (about 10.55 kW), which makes direct comparisons with kW-rated units much easier.
- For electric motor sizing, remember that the nameplate horsepower is the mechanical output — the actual electrical input in kW will be higher due to motor efficiency (typically 85–95%). Always divide the output HP by the efficiency rating to find true electrical draw.
- If you're calculating generator fuel consumption, convert the generator's watt rating to kW (divide by 1,000) and multiply by hours of use to get kWh consumed — then use your fuel's energy density for cost estimates.
- When reading European car specs, use the metric horsepower conversion (1 PS = 0.9863 mechanical HP) rather than the standard factor to get an accurate comparison with US horsepower ratings.
- Always double-check which horsepower standard a manufacturer used — motors sold in the US use mechanical HP (745.7 W), but some imported appliance data sheets specify metric HP (735.5 W), which can create a ~1.4% discrepancy that matters in close-tolerance applications.
Key terms
- Watt (W)
- — The SI base unit of power, equal to one joule of energy transferred per second, and the reference unit used internally for all conversions in this tool.
- Kilowatt (kW)
- — A unit of power equal to 1,000 watts, commonly used for electrical appliances, generator ratings, and utility billing.
- Mechanical Horsepower (HP)
- — The standard US unit of mechanical power, defined as exactly 745.69987 watts, originally based on the estimated output of a draft horse.
- BTU per Hour (BTU/hr)
- — A unit of power representing the rate at which energy is transferred, equal to one British Thermal Unit of heat per hour (≈0.2931 watts), widely used in HVAC and heating system ratings.
- Metric Horsepower (PS/CV)
- — A European variant of horsepower equal to 735.499 watts, commonly seen on vehicle specifications outside the United States — slightly less than mechanical horsepower.
- Power Rate vs. Energy
- — Power (measured in watts or horsepower) is the instantaneous rate of energy use, while energy (measured in watt-hours or BTUs) is the total amount consumed over a period of time — an important distinction when sizing equipment or estimating operating costs.