Power Converter

How many watts is 1 horsepower?

One mechanical horsepower (hp or bhp) is 745.7 watts, and one metric horsepower (PS or CV) is 735.499 watts — so the two "horsepower" are about 1.4% apart. The UK quotes brake horsepower (bhp) for car engines, while European manufacturers often print PS, which is why the same engine can be advertised as, say, 148 bhp or 150 PS. Both convert to the same kilowatt figure used in official EU type approval, so kW is the neutral common ground.

To turn horsepower into everyday units yourself: multiply bhp by 745.7 for watts, or by 0.7457 for kilowatts. A 150 bhp family car is therefore 111,855 W, or 111.9 kW — the figure you'd see on its registration documents. Type any value into the converter above and the bhp, PS, kW and BTU/hr fields all fill in at once.

How do you convert kW to horsepower and back?

Multiply kilowatts by 1.34102 to get mechanical horsepower (bhp), or by 1.35962 to get metric PS; to go back, multiply bhp by 0.7457 to return to kW. A 100 kW motor is about 134 bhp or 136 PS, and a 70 kW city car is roughly 94 bhp. These factors come straight from the definitions — 1 bhp = 745.7 W and 1 PS = 735.499 W — so they never change with the seasons or the exchange rate.

Electric-car makers usually publish power in kW rather than horsepower, which is one reason EV specs feel unfamiliar. A 150 kW electric motor is a brisk 201 bhp, and a dual-motor 250 kW performance EV is about 335 bhp. If you also want to compare how quickly that power changes the car's speed, our acceleration converter handles g-force, m/s² and 0–60 figures.

What is the difference between bhp and PS?

BHP (brake horsepower) is based on mechanical horsepower, where 1 hp = 745.7 W, while PS (Pferdestärke, the German for horsepower) is metric horsepower at 1 PS = 735.499 W. Because a PS is the smaller unit, any engine reads as a slightly larger number in PS than in bhp: 1 bhp ≈ 1.014 PS. The gap is under 1.4%, so for everyday comparison they're interchangeable, but a spec sheet that mixes them can make one car look marginally more powerful than it really is.

How do you convert BTU/hr to kW for a boiler?

Divide BTU per hour by 3,412 to get kilowatts, or multiply BTU/hr by 0.000293 — the same thing. So a 30,000 BTU/hr output is about 8.8 kW, and a 24 kW combi boiler is roughly 81,900 BTU/hr. UK heating engineers and Gas Safe paperwork almost always state boiler output in kW, but BTU/hr still turns up in older manuals, imported units and air-conditioning datasheets, so being able to switch between them saves guesswork when you're sizing a system.

Remember that a boiler's output (heat delivered) and its input (gas consumed) are different numbers — efficiency sits between them. The converter treats every field as raw power, so enter the figure you actually want to compare. For heating and cooling loads you may also meet kilocalories per hour (kcal/h): 1 kW ≈ 860 kcal/h.

How long does it take to charge an EV at 7 kW?

Charging time in hours is roughly the battery size in kWh divided by the charger power in kW. A 7 kW home wallbox — the most common UK single-phase installation — adds about 7 kWh, or 25–30 miles of range, every hour, so a 60 kWh electric car goes from nearly empty to full in about 8–9 hours overnight. A standard 3-pin plug only delivers around 2.3 kW, so it takes roughly three times as long, while public rapid chargers rated at 50 kW or 150+ kW work in minutes rather than hours.

This is a neat illustration of why power and energy are different: the kW rating is the speed of the tap, and the kWh is the size of the bucket. Multiply one by time and you get the other. To turn kWh into a running cost at your tariff, use our energy converter for the joules-to-kWh side of the sum.

What do watts, kilowatts, megawatts and gigawatts actually mean?

They're the same unit scaled up in thousands: 1 kW = 1,000 W, 1 MW = 1,000 kW, and 1 GW = 1,000 MW. A watt is one joule of energy delivered per second, so power tells you how fast energy flows, while energy (measured in watt-hours) is power multiplied by time. A 2,000 W kettle running for six minutes uses 0.2 kWh; leave a 5 W phone charger plugged in all day and it uses about the same.

The bigger units describe infrastructure. A single large wind turbine is rated at a few megawatts; a major power station or offshore wind farm is measured in gigawatts, enough to supply a city. For a named worked example you can check against the tool: enter 100 into the kW field and the converter returns 134.1022092 bhp, 135.9621617 PS, 341,214.2 BTU/hr and 0.1 MW — the figures quoted throughout this page, rounded.