Power Converter
Convert between watts, kilowatts, horsepower, and BTU per hour.
Comment ça marche
This converter handles power (the rate of energy transfer or work done) across watts, kilowatts, horsepower, and BTU per hour, converting your value to watts (the SI base unit) first, then from watts into your target unit.
The watt is defined as one joule of energy transferred per second, making it the standard scientific unit of power. A kilowatt is simply 1,000 watts, commonly used for household appliances (a typical microwave runs at 1-1.5 kW) and electric vehicle motors.
Horsepower originated as a way to market early steam engines by comparing their output to the power of a horse, and it persists today mainly in automotive and some industrial contexts. There are actually a few slightly different horsepower definitions (mechanical, metric, boiler), but mechanical horsepower — the most common — equals approximately 745.7 watts.
BTU per hour (British Thermal Units per hour) is common in heating and cooling equipment ratings, especially in the US — a furnace or air conditioner's capacity is often quoted in BTU/hr, representing how much heat energy it can add or remove per hour; 1 watt ≈ 3.412 BTU/hr.
Power and energy are related but distinct concepts worth not confusing: energy is the total amount of work done or capacity to do work (measured in joules or watt-hours), while power is the rate at which that energy is transferred or used (measured in watts) — a 100-watt bulb run for 10 hours uses 1,000 watt-hours of energy, but its power rating stays 100 watts regardless of how long it runs.
For everyday reference: a household hair dryer might use 1,200-1,875 watts, a small car engine might produce 100-150 horsepower (roughly 75-112 kW), and a large central air conditioning system might be rated around 24,000-60,000 BTU/hr — useful benchmarks for sanity-checking a converted power value.
Power ratings are central to electrical safety as well: household circuits and appliances are rated for a maximum power draw, and exceeding it (by plugging in too many high-wattage devices on one circuit) is a common cause of tripped breakers — understanding watts and their relationship to voltage and current (power = voltage × current) underlies these everyday electrical safety limits.
How many watts are in 1 horsepower?
1 hp ≈ 745.7 watts (mechanical horsepower).
What is a watt, precisely?
One joule of energy transferred per second — the SI (International System of Units) standard unit of power.
Why does horsepower vary slightly by definition?
There are a few historical horsepower definitions (mechanical, metric, boiler) that differ slightly in their exact watt equivalent — mechanical horsepower (≈745.7 W) is the most commonly used today.
What's the difference between power and energy?
Energy is the total amount of work done (measured in joules or watt-hours); power is the rate at which that energy is used or transferred (measured in watts) — a device's wattage doesn't change no matter how long it runs.
How many watts are in 1 BTU per hour?
1 BTU/hr ≈ 0.293 watts, or equivalently, 1 watt ≈ 3.412 BTU/hr.
Why is BTU/hr used for air conditioners and furnaces?
It's the traditional US convention for rating heating and cooling capacity, representing how much heat energy the unit can add or remove per hour.
How many kilowatts does a typical car engine produce?
A small car engine might produce roughly 75-112 kW (about 100-150 horsepower), though this varies widely by vehicle size and type.
Can I convert between more than two power units at once?
Yes — the "Quick reference" table below the main converter shows your entered value converted into every other supported power unit simultaneously.
How is electrical power calculated from voltage and current?
Power (watts) equals voltage (volts) multiplied by current (amps) — this relationship underlies why household circuits have wattage limits based on their voltage and amperage rating.
Why does plugging in too many appliances trip a circuit breaker?
Each circuit has a maximum safe power draw; combining multiple high-wattage devices can exceed that limit, and the breaker trips to prevent overheating or fire risk from excess current.