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The Power Converter enables instant, accurate conversion between all major power units used in electrical engineering, automotive, HVAC, and physics. Whether you need to convert watts to horsepower to compare engine performance, kilowatts to BTU/h for air conditioning selection, or horsepower to watts for an electric motor specification, this tool handles all conversions simultaneously.
Power is the rate of energy transfer or conversion — how quickly energy is used or produced. Watts (W) are the SI unit, used for electrical appliances, solar panels, and scientific calculations. Kilowatts (kW) are used for larger electrical systems, electric vehicles, and home energy. Horsepower (hp) is used in the US and some other countries for engine and motor ratings. BTU per hour (BTU/h) is the standard for HVAC and heating equipment in the US. Foot-pounds per second (ft·lb/s) appears in mechanical engineering.
Power conversions are critical for electrical system sizing, engine performance comparison, HVAC selection, and renewable energy planning.
All power values are converted to Watts (W) as the base unit, then converted to each output.
Convert to Watts:
Convert Watts to outputs:
The mechanical horsepower (1 hp = 745.699872 W) was defined by James Watt based on how much work a horse could do in a minute, and later standardized. Note: metric horsepower (PS) = 735.5 W, slightly different from mechanical hp.
Power reference points: a standard light bulb uses 60W (incandescent) or 8–10W (LED). A microwave runs at 700–1200W. A typical home uses 1–5 kW average power (10–15 kWh/day). A car engine produces 100–300 hp (75–224 kW). A 1-ton air conditioner = 12,000 BTU/h = 3,517 W = 3.517 kW. The human body at rest produces about 80W of heat. A professional cyclist at peak effort produces about 400W (0.54 hp).
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A 200 hp engine produces approximately 149.1 kW. This conversion is essential when comparing US and European vehicle specifications (US uses hp, Europe uses kW).
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A 5 kW solar system produces approximately 17,061 BTU/h. This comparison is useful when sizing solar backup for HVAC systems rated in BTU/h.
1 kilowatt (kW) = 1,000 watts (W). Watts are used for smaller appliances (a 60W light bulb, an 800W microwave). Kilowatts are used for larger systems (a 5 kW solar system, a 150 kW car engine). Electricity bills charge for kilowatt-hours (kWh) — the energy consumed when 1 kW operates for 1 hour.
One mechanical horsepower (hp) = 745.699872 Watts. Note that there is also metric horsepower (PS or CV) = 735.5 W, used in Europe. When comparing car specifications between US (hp) and European (kW) models, use 1 hp = 0.7457 kW. For example, 100 hp ≈ 74.6 kW.
BTU per hour (BTU/h) is the measure of how much heat an air conditioner removes per hour. A 1-ton AC = 12,000 BTU/h = 3.517 kW. To convert BTU/h to watts, divide by 3.41214. For sizing, rooms typically need 20 BTU per square foot — a 500 sq ft room needs about 10,000 BTU/h (approximately 2.9 kW).
A watt is the rate of energy transfer equal to one joule per second (1 W = 1 J/s). It is named after James Watt, who improved the steam engine. In practical terms: a typical human at rest generates about 80W of metabolic heat; a 100W light bulb converts 100 joules of electrical energy to light and heat every second.
Multiply kW by 3,412.14 to get BTU/h. For example, a 3.5 kW air conditioner provides 3.5 × 3,412 = 11,942 BTU/h (approximately 1 ton of cooling). Conversely, divide BTU/h by 3,412.14 to get kW. This conversion is essential for comparing HVAC equipment rated in different units.
Mechanical horsepower (hp) = 745.7 W — used in the US for automobiles, engines, and motors. Metric horsepower (PS or CV) = 735.5 W — traditionally used in Europe, Germany, France, and Japan for vehicle ratings. The difference is about 1.4%. Modern European car specifications increasingly use kW instead of PS, but PS still appears in older documents and some manufacturers.
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