Power Converter

Convert between watts, kilowatts, horsepower, BTU per hour, and metric horsepower — for engines, appliances, HVAC, and electricity.

Power

W, kW, hp, BTU/h

From

Result

0.001

1 W = 0.001 kW

Popular conversions

What Is a Power Converter?

A power converter translates a rate of energy use between units — watts to horsepower, kilowatts to BTU per hour, and so on. Power is energy per unit time, and the SI unit is the watt (W): one joule per second. Engines are rated in horsepower, appliances in watts, air conditioners in BTU per hour, and power plants in megawatts — all measuring the same thing, the rate at which work is done.

This converter routes through the watt with exact ratios. It distinguishes the two horsepowers — mechanical/imperial hp (745.7 W) and metric hp or PS (735.5 W) — and bridges the BTU-per-hour ratings of heating and cooling to the kilowatts of electrical engineering.

This is one category of the full Unit Converter — pair it with our percentage calculator or scientific calculator for related everyday maths.

How Power Conversion Works

Everything routes through the watt

Each unit has a fixed watt factor. The converter turns your input into watts, then projects it into every other power unit so all outputs agree.

Power is energy per second

1 W = 1 J/s. Power tells you how fast energy flows; multiply by time to get the energy used (watts × hours = watt-hours).

Two horsepowers exist

Mechanical horsepower is 745.7 W; metric horsepower (PS, used in Europe) is 735.5 W — about 1.4% less. Car specs can use either.

BTU/h for thermal power

Heating and cooling use BTU per hour: 1 BTU/h ≈ 0.293 W. A 12,000 BTU/h AC unit moves about 3.5 kW of heat.

Core Power Conversion Factors

Multiply to reach watts; divide to come back. Mind which horsepower you mean.

hp → W

× 745.7

One mechanical (imperial) horsepower is 745.7 watts. Metric hp (PS) is 735.5 W.

kW → hp

× 1.341

One kilowatt is 1.341 mechanical horsepower. A 100 kW engine is about 134 hp.

BTU/h → W

× 0.293071

One BTU per hour is 0.293 watts. Used to convert HVAC ratings to electrical power.

How to Use the Power Converter

1
Enter the power value
Type the power rating you want to convert — an engine output, an appliance draw, an HVAC capacity.
2
Choose the 'from' unit
Pick watts, kilowatts, horsepower, metric hp, or BTU per hour.
3
Choose the 'to' unit
Select the target unit, or swap the two to reverse direction.
4
Read every unit at once
The all-units table shows the power in watts, kW, hp, and BTU/h together for a quick cross-check.

Key Power Concepts

Watt

The SI unit of power: one joule per second. A modern LED bulb draws ~10 W; a kettle ~2,000 W; a car engine tens of kilowatts.

Horsepower

A traditional unit from James Watt's comparison to draft horses. Mechanical hp is 745.7 W; the metric PS used in Europe is 735.5 W.

BTU per hour

A thermal-power unit for heating and cooling. One 'ton' of air conditioning is 12,000 BTU/h ≈ 3.5 kW.

Power vs energy

Power (watts) is a rate; energy (watt-hours, joules) is the total used over time. A 1,500 W heater run for 2 hours uses 3 kWh.

Real-World Power Conversions

🚗

Engine output

A 150 hp engine is about 112 kW (or 152 metric PS). European and US car specs flip between kW, hp, and PS.

❄️

Air conditioner

A 12,000 BTU/h AC unit is 3.5 kW of cooling. AC capacity is sold in BTU/h or 'tons' (1 ton = 12,000 BTU/h).

💡

Appliances

A 1,500 W space heater is 2.01 hp of heat output; a 60 W bulb is 0.08 hp. Watts dominate household ratings.

⚡

Power plants

A 500 MW generator could power ~400,000 homes. Grid-scale power is quoted in megawatts and gigawatts.

🏍️

Motorcycle and tools

A 10 hp motor is 7.46 kW; a 750 W power tool is 1 hp. Small motors mix hp and watts freely.

🌬️

Wind turbine

A 2 MW turbine is about 2,682 hp. Renewable capacity is rated in kilowatts and megawatts.

Best Practices for Power Conversion

✓Specify which horsepower. Mechanical hp (745.7 W) and metric PS (735.5 W) differ by ~1.4%. European specs often use PS, so confirm before comparing engine outputs.
✓Keep power and energy separate. Watts are a rate; watt-hours are a total. To get energy used, multiply power by the running time — don't convert one into the other.
✓Use BTU/h for HVAC, kW for electrical. Heating and cooling capacity is BTU/h; electrical draw is watts. Convert between them with the 0.293 factor when sizing systems.
✓Mind input vs output power. A motor's rated output (mechanical) is less than its electrical input because of efficiency losses. Don't equate the two.
✓Round to the rating's precision. Engine and appliance ratings are nominal. Reporting 149.8 hp from a '150 hp' engine implies precision the spec doesn't claim.

Common Power Conversion Mistakes

Confusing the two horsepowers

Using mechanical hp where metric PS is meant (or vice versa) gives a ~1.4% error — small but real when comparing engine specs.

Treating watts as energy

Watts are power, not energy. A '2 kW' appliance uses 2 kWh only if run for one hour; the time dimension can't be dropped.

Reading BTU/h as BTU

HVAC ratings are a power (BTU per hour). Treating them as total energy (BTU) ignores the time over which the heat moves.

Ignoring efficiency losses

A motor's electrical input exceeds its mechanical output. Converting input watts straight to output horsepower overstates the useful power.

Why Power Conversion Matters

Power ratings drive purchasing and sizing decisions across vehicles, appliances, HVAC, and the electrical grid — and the units are a patchwork of watts, two different horsepowers, and BTU per hour. Picking the wrong horsepower or confusing power with energy can mislead an engine comparison, an air-conditioner purchase, or an electricity-cost estimate.

Because power is energy per second, it connects directly to running costs (power × time × price) and to system capacity. A converter that routes through the watt with exact factors — and keeps mechanical hp, metric PS, and BTU/h straight — lets a buyer, mechanic, or engineer compare ratings on a true, apples-to-apples basis.

Built for car buyers, mechanics, HVAC installers, electricians, and engineers converting between watts, horsepower, and BTU/h.

Linear unit factors follow the BIPM SI brochure, the NIST Guide to the SI, and ISO 80000. Currency rates load live from open.er-api.com; crypto prices from CoinGecko. See our methodology and editorial policy. Educational only — not certified for regulated trading, settlement, medical, or aerospace use.

Power Converter FAQs

Multiply mechanical horsepower by 745.7 to get watts. So a 150 hp engine is about 111,855 W, or 111.9 kW. Note that metric horsepower (PS), common in Europe, is 735.5 W, so the two horsepowers differ by about 1.4% — always confirm which is meant.

Exactly 1,000 watts. A kilowatt (kW) is just 1,000 W, and a megawatt (MW) is 1,000 kW (a million watts). Appliances are usually rated in watts, car engines and home electrical loads in kilowatts, and power plants in megawatts.

Mechanical (imperial) horsepower is 745.7 W, while metric horsepower — abbreviated PS or CV — is 735.5 W, about 1.4% less. European car makers often quote PS, so a '150 PS' car is roughly 148 mechanical hp. The difference is small but matters when comparing spec sheets.

Multiply BTU/h by 0.293071 to get watts. So a 12,000 BTU/h air conditioner is about 3,517 W (3.5 kW) of cooling power. Note that HVAC ratings are BTU per hour — a power — not total BTU, which would be an amount of energy.

No. Power (watts, horsepower, BTU/h) is the rate at which energy is used; energy (joules, kilowatt-hours) is the total amount. A 1,500 W heater draws power at a constant rate, but the energy it consumes depends on how long it runs: 1,500 W for 2 hours is 3 kWh.

It uses standard definitions (1 hp = 745.69987 W, 1 metric hp = 735.49875 W, 1 BTU/h = 0.293071 W) and routes every conversion through the watt at full precision, so the result is exact to your input precision.