Power Converter

Power Converter

This converter transforms values between seven common power units: watts, kilowatts, megawatts, horsepower, BTU/hour, calories per second, and foot-pounds per second. Whether you are comparing motor ratings, sizing HVAC equipment, or translating specs between metric and imperial systems, enter a value and select your units to get an instant result. Power units appear across automotive datasheets, appliance labels, utility bills, and engineering handbooks — often in incompatible systems that need quick translation.

How Power Conversion Works

All conversions use the watt (W) as the base unit. Each input value is first converted to watts, then divided by the target unit’s factor to reach the result:

• Result = input x (source factor in W) / (target factor in W)
• 1 kilowatt (kW) = 1,000 W
• 1 megawatt (MW) = 1,000,000 W
• 1 mechanical horsepower (hp) = 745.699 W
• 1 BTU/hour = 0.29307 W
• 1 calorie/second (cal/s) = 4.18400 W
• 1 foot-pound/second (ft-lbf/s) = 1.35582 W

To convert 5 kW to horsepower: 5,000 W / 745.699 = 6.705 hp. To convert 100,000 BTU/h to kW: 100,000 x 0.29307 / 1,000 = 29.307 kW.

Worked Examples

Example 1 — Sizing a home generator. A household needs to run a refrigerator (400 W), a sump pump (750 W), lights (300 W), and a window AC unit (1,500 W). Total load: 2,950 W. Converting to generator rating terms: 2,950 / 745.699 = 3.96 hp of continuous output required. Most portable generators are sold in watts, so 3,000 W covers this with no headroom; 4,000 W provides a safe 35% buffer.

Example 2 — Comparing a car engine to its kW equivalent. A 2024 mid-size truck is rated at 400 hp. In kW: 400 x 745.699 / 1,000 = 298.3 kW. European specs for the same engine would list it at approximately 298 kW — useful when reading international automotive reviews.

Example 3 — Matching a furnace to a heat pump. A gas furnace is rated at 80,000 BTU/h output. In watts: 80,000 x 0.29307 = 23,446 W (23.4 kW). A replacement heat pump would need at least 23 kW of heating capacity at design-day outdoor temperatures to match that output.

Power Unit Reference Table

When to Use This Converter

• You are reading a vehicle spec sheet from a European manufacturer that lists power in kW and need to compare it to a US spec in horsepower
• You are sizing a backup generator and need to add up appliance wattages from nameplates rated in BTU/h or horsepower
• You are replacing a gas furnace with a heat pump and need to match BTU/h output to kW capacity
• You are reviewing solar panel or battery storage specs listed in watts and comparing them to utility billing rates in kilowatts
• You are working through a mechanical engineering problem where power is given in foot-pounds per second and needs to convert to SI watts

Common Mistakes

1. Confusing horsepower variants. Mechanical hp (745.7 W) is most common in the US. Metric hp (PS, 735.5 W) appears in European auto specs. Electric hp and boiler hp have different values entirely — always check which variant the datasheet uses.
2. Treating input power as output power. Motor nameplates often list shaft output power in hp or kW. The actual electrical power drawn from the wall is higher by a factor of 1 / efficiency (typically 85-95% for motors). A 5 hp motor drawing 3,728 W of shaft power consumes roughly 4,100-4,400 W from the grid.
3. Forgetting the BTU/h scale. Because 1 BTU/h is only 0.293 W, large HVAC numbers look enormous in BTU/h but are modest in kW. A 36,000 BTU/h AC unit is just 10.5 kW — easy to underestimate when working with six-digit BTU figures.
4. Mixing power and energy. Watts (W) and kilowatts (kW) measure the rate of energy use. Kilowatt-hours (kWh) measure total energy consumed over time. The converter handles power rates only — to find energy, multiply power by time in hours.

Quick Reference Benchmarks

• LED light bulb: 7-15 W
• Laptop computer: 30-65 W
• Refrigerator: 100-400 W
• Space heater: 1,500 W (1.5 kW)
• Window AC (12,000 BTU/h): 1,000-1,400 W
• Electric vehicle charger (Level 2): 7,200-19,200 W (7.2-19.2 kW)
• Typical passenger car engine: 100-200 hp (75-149 kW)
• Utility-scale wind turbine: 2-5 MW

Tips

1. To convert a car engine rating quickly, remember 1 hp = 0.746 kW — a 200 hp engine produces roughly 149 kW
2. For HVAC sizing, 1 ton of cooling equals 12,000 BTU/h, which is approximately 3.52 kW
3. When comparing electric motors, rated horsepower refers to shaft output power; wattage on the nameplate may refer to electrical input power, which is higher
4. Solar panel output is rated in watts DC; inverter output is in watts AC and is about 2-4% lower due to conversion losses
5. European car brochures often list power in PS (metric horsepower) rather than hp — multiply PS by 0.9863 to get US hp, or convert both to kW for a clean comparison
6. BTU/h to watts: multiply BTU/h by 0.29307. Watts to BTU/h: multiply by 3.4121. Keep these two factors on hand for HVAC work