Power Unit Converter -- Watts, HP, BTU/h & More

Convert Power Units

This power unit converter converts between watts, kilowatts, megawatts, horsepower (mechanical and metric), BTU per hour, foot-pounds per second, and calories per second. Enter a value and select the source unit to see all conversions instantly.

Quick Reference Table

Common power conversions, pre-calculated for quick lookup.

Real-World Power Examples

It helps to anchor abstract numbers to things you already know. Here are approximate power ratings for common devices and systems.

Power Units Explained

Watt (W)

The watt is the SI unit of power, named after James Watt. One watt equals one joule of energy transferred per second. Watts measure the rate of energy use — how fast energy is consumed or produced, not how much total energy is used.

Kilowatt (kW) and Megawatt (MW)

Kilowatts and megawatts are simply larger multiples of the watt. One kilowatt = 1,000 watts; one megawatt = 1,000,000 watts. Kilowatts are commonly used for household appliances and electric vehicles. Megawatts are used for power plants and industrial systems.

Mechanical Horsepower (hp)

Mechanical (or imperial) horsepower is defined as 550 foot-pounds per second, which equals approximately 745.7 watts. It originated as a way to compare steam engine output to the work capacity of draft horses. It is the standard in the US and UK for engines and motors.

Metric Horsepower (PS / CV)

Metric horsepower is defined as the power to raise 75 kilograms by 1 meter in 1 second, which equals approximately 735.5 watts. It is called PS (Pferdestärke) in German and CV (cheval-vapeur) in French. Car specifications in Europe and Asia typically use metric HP.

BTU per Hour (BTU/h)

BTU/h measures thermal power — how much heat is produced or removed per hour. It is the standard rating for HVAC systems (air conditioners, heaters, furnaces) in the US. One BTU is the energy needed to raise one pound of water by one degree Fahrenheit.

Foot-Pound per Second (ft·lbf/s)

A foot-pound per second is the power needed to move one pound-force through one foot in one second. It is the basis of the mechanical horsepower definition (1 hp = 550 ft·lbf/s). It occasionally appears in engineering and physics contexts.

Calorie per Second (cal/s)

A calorie per second measures the rate of heat energy transfer using the thermochemical calorie. One cal/s equals 4.1868 watts. This unit is sometimes encountered in chemistry and nutrition science contexts.

Common Conversion Formulas

Watts ↔ Kilowatts

Example: 2,400 W = 2.4 kW. A 2.4 kW heater draws 2,400 watts.

Watts ↔ Horsepower (mechanical)

Example: 150 hp × 745.7 = 111,855 W ≈ 111.9 kW.

Kilowatts ↔ Horsepower

Example: 100 kW × 1.341 = 134.1 hp.

Watts ↔ BTU/h

Example: A 5,000 BTU/h air conditioner = 5,000 × 0.2931 = 1,465.5 W ≈ 1.47 kW.

kW vs. kWh: Power vs. Energy

A common point of confusion: kW (kilowatts) measures power — the rate of energy use at any instant. kWh (kilowatt-hours) measures energy — the total amount used over time. Running a 2 kW appliance for 3 hours consumes 6 kWh of energy. Your electricity bill is in kWh, not kW.

Frequently Asked Questions

How many watts are in one kilowatt?

One kilowatt equals exactly 1,000 watts. To convert kilowatts to watts, multiply by 1,000. To convert watts to kilowatts, divide by 1,000. For example, 3,500 W = 3.5 kW.

How do I convert watts to horsepower?

Divide the number of watts by 745.7 to get mechanical horsepower. For example, 1,500 W ÷ 745.7 ≈ 2.01 hp. For metric horsepower (PS), divide by 735.5 instead: 1,500 ÷ 735.5 ≈ 2.04 PS.

What is the difference between mechanical and metric horsepower?

Mechanical (imperial) horsepower equals 745.7 watts and is standard in the US and UK. Metric horsepower (PS/CV) equals 735.5 watts and is standard in continental Europe and Asia. The difference is about 1.4%. When reading car specifications, check whether the rating is in hp or PS.

How do I convert BTU per hour to watts?

Multiply BTU/h by 0.29307 to get watts, or divide by 3.412 for the same result. For example, 12,000 BTU/h (a common "1 ton" AC unit) = 12,000 × 0.29307 = 3,517 W ≈ 3.5 kW.

What is a watt in simple terms?

A watt measures how fast energy is used or produced. One watt = one joule per second. A 100-watt light bulb uses 100 joules of energy every second. Higher wattage means faster energy consumption.

How many kilowatts does a typical house use?

A typical US home averages about 1.2 kW of continuous power draw (roughly 10,500 kWh per year). Peak demand during hot summer afternoons with air conditioning running can reach 5–10 kW. A single 120V household circuit is usually rated for 1.8–2.4 kW.

What is the difference between kW and kWh?

kW (kilowatts) measures power — the instantaneous rate of energy transfer. kWh (kilowatt-hours) measures energy — the total amount used over time. Running a 2 kW heater for 3 hours uses 2 × 3 = 6 kWh of energy. Your electricity bill charges per kWh.

How much horsepower does an electric car have?

Electric car motors are rated in kW, then often converted to hp for marketing. A Tesla Model 3 Standard Range produces about 211 kW (283 hp). A Nissan Leaf produces about 110 kW (148 hp). Electric motors deliver full torque instantly, so even lower-hp EVs can feel fast.

Privacy & Limitations

• Client-side only. No data is sent to any server. No cookies, no tracking.
• Mechanical horsepower uses the standard 745.69987 W factor. Metric horsepower (PS) uses 735.49875 W. Boiler horsepower and electrical horsepower are not included.
• BTU/h uses the International Table BTU (1 BTU = 1,055.06 J). Some sources use the thermochemical BTU (1,054.35 J), which differs by <0.07%.

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