Horsepower (Metric) to BTU (IT)/second

EU regulations require engine power in kilowatts, but consumers prefer a familiar number. Continental Europe adopted metric horsepower (PS) in the 19th century, and car culture cemented it. Germans say "PS," French say "CV," Italians say "CV" too. The UK uses "bhp" (British horsepower). A 200 PS car is 197 hp — close enough that most people don't notice the 1.4% difference. Japanese manufacturers use PS as well (sometimes written 馬力).

In a light car (1,000 kg), 100 PS gives a power-to-weight ratio of 100 PS/tonne — adequate for city driving with 0–100 km/h in about 10–11 seconds. In a heavy SUV (2,000 kg), 100 PS feels sluggish, struggling on hills and taking 15+ seconds to reach highway speed. The magic number for "fun" is roughly 150–200 PS per tonne — which is why a 90 PS Mazda MX-5 (1,000 kg) feels livelier than a 200 PS family SUV (1,800 kg).

As of 2025, the Rimac Nevera holds the production EV record at 1,914 PS (1,408 kW). For combustion engines, the Bugatti Chiron Super Sport delivers 1,600 PS. Koenigsegg's Jesko Absolut produces 1,600 PS. But the real mind-bender is that a Formula 1 car's power unit produces about 1,050 PS from just 1.6 liters — over 650 PS per liter, achieved through turbocharging and energy recovery systems at 15,000 RPM.

Because they're defined differently. British hp = 550 ft·lbf/s = 745.7 W. Metric hp = 75 kgf·m/s = 735.5 W. The metric definition uses round metric numbers (75 kg, 1 m, 1 s) rather than being an exact conversion of the British unit. The ~1.4% gap is small enough that it rarely matters practically, but it means a car rated at 200 PS is technically 197 hp. Marketing departments sometimes quietly use whichever number is larger.

Both, depending on market. Tesla lists kW in tech specs but PS/hp in consumer marketing because buyers understand horsepower intuitively. A Tesla Model 3 Performance produces about 460 PS (340 kW). The shift toward kW is accelerating because EVs make the kW connection obvious — if you charge at 11 kW and your motor outputs 150 kW, the relationship is clear. Eventually kW may replace PS entirely, but decades of "how many horses?" thinking won't die easily.

In US combustion engineering and power plant heat rate analysis, fuel energy content is natively specified in BTU (natural gas is sold per therm = 100,000 BTU). Expressing burner output in BTU/s keeps the calculation in one unit system, avoiding constant conversions. When your fuel flow is in BTU/min and your efficiency calculations use BTU, switching to watts mid-calculation just creates errors.

One BTU/s ≈ 1,055 watts — roughly a single-bar electric fire or a small hair dryer. It's a surprisingly human-scale unit. A typical US home gas furnace running at full blast produces about 28 BTU/s (100,000 BTU/h ÷ 3,600). A gas stovetop burner on high delivers about 3–5 BTU/s. So BTU/s lands right in the range where you can feel the heat on your face.

Power plant thermal engineering (heat rate analysis), industrial furnace and kiln design, jet engine combustion analysis, and rocket propulsion engineering. NASA specifications for rocket engines often include BTU/s figures. The Space Shuttle Main Engine produced about 12 million BTU/s of thermal power. Steelmaking blast furnaces operate at 50,000–200,000 BTU/s of heat input.

One BTU/s = 1.415 mechanical horsepower, or roughly 1.4 hp. This is useful in automotive and engine testing where dynamometers may report in BTU/s for thermal measurements but engineers think in horsepower. A 400 hp engine rejects about 280 BTU/s through its cooling system at full power (assuming 60% of fuel energy becomes waste heat). The conversion factor is easy to remember: multiply BTU/s by 1.4 to get hp.

The BTU originated as a water-heating energy unit, with several temperature-dependent variants. This converter uses the fixed International Table variant: 1 BTU(IT) = exactly 1,055.05585262 J. BTU-based energy and power units remain common in U.S. thermal engineering, equipment ratings and fuel-energy quantities. BTU alone measures energy; BTU per second, minute or hour measures power.