Power Converter
Convert Watts, Horsepower, and BTUs. Plus, estimate your electricity costs.
Metric & Electrical
Mechanical & HVAC
Standard Mechanical HP
Power Context
Explore More Unit Converters
Mastering the Flow of Energy
Power is the heartbeat of modern civilization. From the tiny electrical impulses in your brain (20 Watts) to the massive turbines powering cities (Megawatts), understanding power units is essential for engineers, mechanics, and homeowners alike. Use our tools to bridge the gap between abstract numbers and real-world costs.
Advanced Tool Features
Bill Estimator
Stop guessing your electric bill. Enter a device's wattage and usage to see exactly what it costs you per month.
True Horsepower
We distinguish between Mechanical HP (US/UK) and Metric HP (EU), ensuring your engine stats are accurate.
Power Context
Visualize abstract Watts as "LED Bulbs", "Cyclists", or "Horses". Great for teaching and understanding scale.
HVAC Ready
Instantly convert BTU/h to Kilowatts. Essential for sizing air conditioners and heaters.
SI Precision
All calculations are anchored to the standard Watt, providing scientific accuracy relative to NIST standards.
Smart Presets
Quickly load values for common items like a "Human Heart" or "Tesla Model S" to see their power stats.
How to Use the Power Converter
- Converter Tab: Enter a value in any field (e.g., Horsepower). All other units (Watts, BTU/h) update instantly.
- Use Presets: Tap "Lightbulb" or "Sports Car" to populate the fields with real-world examples.
- Bill Estimator: Switch to the 💸 tab. Enter your device's wattage and how many hours you use it daily to see the yearly cost.
- Check Visuals: The dark "Power Context" box at the bottom shows you what that power level actually represents in the real world.
Power Conversion Cheat Sheet
| To Convert From | To Watts (W) | Formula |
|---|---|---|
| Horsepower (cal/mech) | 745.7 W | hp × 745.7 |
| Horsepower (metric) | 735.5 W | hp(M) × 735.5 |
| Kilowatt (kW) | 1,000 W | kW × 1,000 |
| BTU per Hour | 0.293 W | BTU/h ÷ 3.412 |
Common Mistakes to Avoid
- Confusing kW and kWh:
This is the classic error. kW is the rate (like speed). kWh is the amount (like distance). You pay for kWh, not kW.
- Mixing up Horsepower Types:
American cars use Mechanical HP (746W). European specs often use Metric HP (736W). The difference is small (1.4%) but important for precision engineering.
Pro Tips for Power Math
- The "Rule of 10".
For a rough estimate, 1 Horsepower is a bit less than 1 Kilowatt (0.75 kW). So a 100hp engine is roughly 75 kW.
- Bill Estimation.
To quickly guess the cost of a device running 24/7 for a year: Multiply its Wattage by $1. (At average US rates, 1 Watt 24/7/365 ≈ $1.30/year).
Frequently Asked Questions
Expert answers to your energy questions.
What is the difference between Mechanical and Metric Horsepower?
Mechanical Horsepower (hp), used in the US and UK, is approximately 745.7 Watts. Metric Horsepower (PS, cv, hk), used in Europe and Asia, is slightly smaller at 735.5 Watts. Always check which standard your engine uses.
How do I calculate electricity cost for a device?
Use our Bill Estimator tab! The formula is: (Watts × Hours Used / 1000) × Cost per kWh. For example, a 100W bulb used for 10 hours uses 1 kWh. At $0.15/kWh, that costs $0.15.
What is a Watt?
A Watt (W) is the standard unit of power, named after James Watt. It measures the rate of energy transfer. One Watt equals one Joule per second. Think of it as the 'speed' of energy flow.
How many BTUs are in 1 Ton of cooling?
In HVAC, 1 Ton of refrigeration equals 12,000 BTU/hour. This can cool roughly 500-1,000 square feet of living space, depending on insulation and climate.
Why do cars use Horsepower instead of Watts?
Tradition! James Watt invented the term to sell steam engines by comparing them to draft horses. While electric cars (EVs) are technically rated in Kilowatts (kW), manufacturers still advertise 'Horsepower' because consumers understand it better.
What is 'Vampire Power'?
Vampire Power (or Phantom Load) refers to the electricity consumed by devices when they are turned off but plugged in (like TVs or chargers). This can account for 5-10% of your monthly bill.
How many Watts does a human generate?
At rest, a human generates about 100 Watts of heat (mostly from metabolism). During intense cycling or sprinting, a pro athlete can sustain 300-400 Watts for an hour, or burst up to 1,500 Watts for a few seconds.
Kilowatt (kW) vs Kilowatt-hour (kWh)?
kW is Speed, kWh is Distance. kW measures how fast you are using energy right now. kWh measures the total amount you used. A 1 kW heater running for 1 hour uses 1 kWh of energy.
How many Watts in 1 Amp?
You need to know the Voltage! The formula is Watts = Volts × Amps. In a standard US outlet (120V), 1 Amp = 120 Watts. In a car (12V), 1 Amp = 12 Watts.
What is the power of the Sun?
The Sun emits about 3.8 × 10^26 Watts. In comparison, the entire human civilization uses about 18 Terawatts (1.8 × 10^13 W).
Does a 60W LED bulb consume 60 Watts?
No! '60W Equivalent' LEDs actually consume only 8-10 Watts. The '60W' label just means it produces the same brightness (lumens) as an old incandescent bulb.
How do I convert BTU/h to Watts?
Divide BTU/h by 3.412. For example, a 12,000 BTU/h (1 Ton) air conditioner uses roughly 3,516 Watts of cooling power.