Power Converter

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HP • kW • W • BTU/hr • cal/s

Power Value ⓘ

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Enter a power value to convert

How to Use the Power Converter

Enter a power value — e.g. 100 for 100 horsepower, or 5000 for 5000 watts.
Select From unit — HP (US engine standard), kW (European/electric), W (appliances), BTU/hr (HVAC), or metric HP.
HP types note — this uses mechanical HP (US). Metric HP (PS/CV) = 735.499 W. Electrical HP = 746 W exactly. All differ slightly.
Results show HP, kW, W, BTU/hr all at once for easy comparison.

Benefits

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Vehicle Comparison

Compare US car specs (HP) with European car specs (kW) when researching imported vehicles.

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HVAC & Appliances

Convert BTU/hr to kW for air conditioners, heaters, and heat pumps. 1 ton cooling = 12,000 BTU/hr = 3.517 kW.

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EV Power

Electric vehicles are rated in kW. Convert to HP for familiar comparison — Tesla Model 3: 283 HP = 211 kW.

Power Conversion Guide — Horsepower, Kilowatts, Watts, BTU/hr

Power conversion is needed when comparing US vehicles (rated in HP) to European and electric vehicles (rated in kW), evaluating HVAC systems (BTU/hr vs kW), or understanding electrical appliances. The key conversion: 1 HP = 745.7 watts = 0.7457 kW. A 200 HP sports car = 149.14 kW. A Tesla Model 3 Performance at 450 HP = 335.6 kW.

HVAC: Air conditioners are rated in BTU/hr or "tons." 1 ton of cooling = 12,000 BTU/hr = 3.517 kW. A typical 2-ton AC = 24,000 BTU/hr = 7.03 kW. Electrical: a 100-watt lightbulb = 0.1 kW = 0.1341 HP. The average US home uses about 1.2 kW on average (10,500 kWh/year ÷ 8,760 hours). Solar panels are rated in watts: a 400W panel produces 400 Wh of energy per hour of full sun.

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Vehicle Power Reference

Economy car: 100–150 HP = 74.6–111.9 kW. Mid-size sedan: 180–250 HP = 134–186 kW. Sports car: 300–500 HP = 224–373 kW. Supercar: 600–1000 HP = 447–746 kW. Semi-truck: 400–600 HP.

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HVAC Reference

1 ton = 12,000 BTU/hr = 3.517 kW. 1.5 ton = 18,000 BTU/hr = 5.28 kW. 2 ton = 24,000 BTU/hr = 7.03 kW. 3 ton = 36,000 BTU/hr = 10.55 kW. 5 ton = 60,000 BTU/hr = 17.58 kW.

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Electrical Appliances

LED bulb: 9W = 0.009 kW. Hair dryer: 1,800W = 1.8 kW. Microwave: 1,000W = 1 kW. Electric oven: 5,000W = 5 kW = 6.7 HP. EV charger (Level 2): 7,200W = 7.2 kW = 9.7 HP.

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Renewable Energy

Home solar system: 6–10 kW peak. Wind turbine (residential): 5–10 kW. Large wind turbine: 3–15 MW = 3,000–15,000 kW. Hoover Dam output: 2,080 MW = 2.08 million kW = 2.79 million HP.

Formula & Logic

Power is energy per unit time, and its units carry an unusually literal history. James Watt defined horsepower in the 1780s by measuring how much a dray horse could lift, specifically 33,000 foot-pounds per minute, in order to sell steam engines against the animals they replaced. That marketing definition survives as mechanical horsepower, 745.6999 watts. Metric horsepower, used in European vehicle documents, is slightly smaller at 735.5 W, so a car quoted at 300 PS is not quite 300 hp — a discrepancy of about 1.4% that appears in every cross-market spec sheet.

watts = value × factor_fromresult = watts ÷ factor_to1 hp (mechanical) = 745.6999 W · 1 PS (metric) = 735.49875 W · 1 BTU/h = 0.29307 W

where:

watt: SI unit — one joule per second
hp: mechanical horsepower, 550 ft·lb per second
PS: Pferdestärke, metric horsepower, 1.4% smaller than hp
ton: of refrigeration: 12,000 BTU/h, the rate to freeze one short ton of ice per day

Assumptions: Engine output figures also depend on the measurement standard (SAE net, DIN, ECE), which can differ by several percent on the same engine independently of the unit used.

SourceNIST unit conversion

Step-by-Step Example: A 300 hp Engine in kW and PS

A US-market power figure translated for a European specification sheet.

Rated output300 hp (mechanical)

To watts: 300 × 745.6999 = 223,710 W.
To kilowatts: 223,710 ÷ 1,000 = 223.71 kW.
To metric horsepower: 223,710 ÷ 735.49875 = 304.16 PS.
Note the direction: because PS is the smaller unit, the PS number is larger than the hp number.
Sanity-check the ratio: 304.16 ÷ 300 = 1.0139, the expected 1.4% gap.

Result300 hp = 223.71 kW = 304.16 PS

This is why a car advertised at "304 PS" in Germany and "300 hp" in the US is the same engine, not a more powerful variant. Air conditioning uses a third convention entirely: a 3-ton unit is 36,000 BTU/h, about 10.5 kW of cooling.

Power Conversion FAQ

How many watts in a horsepower? ▾

1 mechanical horsepower (HP) = 745.69987 watts ≈ 745.7 W. Therefore, 1 kW = 1,000 W = 1.34102 HP. Common car conversions: 100 HP = 74.57 kW. 200 HP = 149.14 kW. 300 HP = 223.71 kW. 400 HP = 298.28 kW. 500 HP = 372.85 kW. For EVs: Tesla Model 3 350 HP = 261 kW. The term "horsepower" was coined by James Watt in the 1780s to market steam engines — he calculated a horse could do 33,000 foot-pounds of work per minute.

What is the difference between US horsepower and metric horsepower? ▾

US mechanical HP = 745.699 W. Metric HP (PS in German, CV in French/Spanish) = 735.499 W — about 1.4% less. European car specs use metric HP (PS) while US specs use mechanical HP. So a German car listed at "300 PS" = 300 metric HP = 295.8 US HP = 220.6 kW. Electric HP = 746 W exactly. Boiler HP = 9,809.5 W (a much larger unit used in industrial settings).

How do you convert BTU/hr to kilowatts? ▾

1 BTU/hr = 0.000293071 kW. Conversely, 1 kW = 3,412.14 BTU/hr. Common HVAC conversions: 12,000 BTU/hr = 3.517 kW (1 ton of cooling). 18,000 BTU/hr = 5.28 kW. 24,000 BTU/hr = 7.03 kW. 36,000 BTU/hr = 10.55 kW. When buying an air conditioner or heat pump, divide the BTU/hr rating by 3,412 to get kW and compare with European energy labels.

How much horsepower does a human produce? ▾

A fit human can sustain about 0.1 HP (75 W) for extended periods. Elite cyclists can sustain 0.4–0.5 HP (300–370 W) for an hour. Tour de France riders peak at about 1 HP (746 W) during short bursts. Usain Bolt peaked at about 3.5 HP (2,619 W) during his 100m world record sprint. So a "100 HP" car has the equivalent of about 1,000 sustained human workers — which is why the industrial revolution was so transformative.

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