Power Converter
Convert between watts, kilowatts, horsepower, and BTU/hr. Used for motor ratings and energy calculations.
Power Converter
Enter a power value and select its unit β all other units update instantly.
Quick References
How to Convert Between Watts, Horsepower, BTU/hr, and Tons of Refrigeration
Your air conditioning quote says you need a 4-ton unit, but the electrician wants the load in kilowatts to size the circuit breaker. Enter 4, select tons, and the converter shows 14.069 kW, 18,864 hp, and 48,000 BTU/hr. The copy button lets you paste the kilowatt figure straight into the electrical load calculation worksheet.
The converter handles 13 units from milliwatts to gigawatts. A mechanic comparing a 200 hp (mechanical) engine with a 150 kW (metric) specification can instantly see that 200 hp = 149.14 kW, confirming the metric engine is slightly less powerful. A homeowner comparing a 1500W space heater to a 20,000 BTU/hr gas heater can see that the gas unit produces about 5.86 kW β nearly four times the output. The quick-reference row shows everyday power levels: a phone charger at 5 W, a laptop at 65 W, a car engine at 111,855 W.
HVAC sizing where the wrong unit wastes thousands
A contractor in Dubai quotes a 5-ton AC system for a villa. The client, used to kilowatts, sees "5" and assumes 5 kW β but 5 tons of refrigeration is actually 17.58 kW. Installing a 5 kW unit instead of a 17.58 kW unit would leave the villa sweltering. The converter makes it explicit: enter 5 tons, see 17.58 kW, 60,000 BTU/hr, and 23,900 kcal/hr. No ambiguity.
A motorsport engineer compares a Japanese engine rated at 180 PS (metric horsepower) with a British engine rated at 175 hp (mechanical). Converting: 180 PS = 177.5 hp. The British engine is actually slightly less powerful. Without converting, the engineer might assume 180 > 175 means the Japanese engine wins, which it does β but by only 2.5 hp, not 5.
An electrician installs a circuit for a 5,000W convection oven. The breaker must handle the load: 5 kW at 240V draws 20.83 amps. Converting 5,000W to BTU/hr gives 17,061 BTU/hr β useful for comparing the oven's heat output to a gas equivalent. The converter helps the electrician work across both the electrical and thermal sides of the same appliance.
Related tools
How the Power Converter Handles Watts, Horsepower, and BTU/hr
Every unit in the converter is stored as a multiple of one watt. When you enter 200 hp (mechanical), the tool multiplies by 745.7 to get 149,140 W, then divides by each target unit's factor. The conversion to kilowatts gives 149.14 kW. The conversion to BTU/hr gives 508,827 BTU/hr. Because all conversions pass through watts in one step, there is no rounding drift from chaining through intermediate units.
Why there are three different horsepowers
Mechanical horsepower (hp) is defined as exactly 550 foot-pounds per second, which equals 745.69987... W. Metric horsepower (PS, from the German PferdestΓ€rke) is defined as exactly 735.49875 W β the power needed to lift 75 kg at 1 m/s. Electrical horsepower is defined as exactly 746 W. The differences are small but real: a 100 hp (mechanical) engine is 101.4 PS (metric) or 99.8 hp (electrical). Car manufacturers choose whichever number makes their engine look best in the target market.
The ton of refrigeration is defined as exactly 12,000 BTU/hr, which equals 3,516.85 W. This represents the cooling power needed to freeze one short ton (2,000 lb) of water at 0Β°C in 24 hours. The definition dates to the era of ice harvesting: a "ton" of ice melting over 24 hours absorbs 12,000 BTU/hr. Modern air conditioners use this unit because it produces convenient whole numbers: a typical home needs 2-5 tons (24,000-60,000 BTU/hr).
Why BTU/hr and watts measure the same thing differently
Watts and BTU/hr both measure power β the rate of energy transfer. 1 watt = 3.41214 BTU/hr. Electric heaters are rated in watts because they consume electricity. Gas furnaces are rated in BTU/hr because they burn fuel. When comparing an electric heater (1,500W = 5,118 BTU/hr) to a gas furnace (40,000 BTU/hr), the gas unit produces about 7.8 times more heat. The converter bridges the unit gap so you can make this comparison directly.
The formatting thresholds handle the enormous range: milliwatts (0.001 W) display with 6-8 decimal places; watts and horsepower use 2-4 decimal places; megawatts and gigawatts use locale-formatted numbers. A smartphone charger at 5 W and a nuclear power plant at 1,000 MW (1 GW) both display clearly without scientific notation obscuring the practical meaning of the number.
Frequently Asked Questions
How many watts is a 3-ton air conditioner?
A 3-ton AC unit produces 36,000 BTU/hr, which equals 10,551 watts (10.55 kW). This means it draws about 44 amps at 240V β requiring a dedicated circuit. The converter shows this instantly: enter 3 tons, see 10.55 kW, 14.1 hp, and 36,000 BTU/hr. For home sizing, a typical house needs 2-5 tons depending on square footage and climate.
What is the difference between power and energy in practical terms?
Power is how fast you use energy. A 100W light bulb uses energy at a rate of 100 joules per second. Energy is the total amount consumed. Running that bulb for 10 hours uses 1 kWh of energy (100W Γ 10h Γ· 1000). Your electricity bill charges for energy (kWh), not power (kW). A 2 kW heater running for 1 hour uses the same energy as a 1 kW heater running for 2 hours.
Why do European car manufacturers use PS instead of hp?
PS (PferdestΓ€rke) is the German metric horsepower, defined as the power needed to lift 75 kg at 1 m/s. It was standardised in Germany in the early 20th century and remains the legal unit for car power ratings in the EU. PS is 1.4% lower than mechanical hp, so a 200 PS engine produces 197.2 hp. Manufacturers sometimes round up β a '200 PS' engine might actually produce 198 PS.
How do I calculate the electricity cost of running a heater?
Multiply the heater's wattage by hours of use, divide by 1,000 to get kWh, then multiply by your electricity rate. A 1,500W heater running 8 hours uses 12 kWh. At $0.12/kWh, that costs $1.44/day. Converting 1,500W to BTU/hr gives 5,118 BTU/hr β useful for comparing to a gas furnace's output per dollar.