Energy and Power — Two Related Concepts
Energy and power are closely related but fundamentally different. Energy is the capacity to do work, measured in joules (J), calories, or kilowatt-hours (kWh). Power is the rate of energy transfer, measured in watts (W). The relationship is simple: Energy = Power × Time. A 100-watt bulb running for 10 hours uses 1 kWh of energy.
Energy Unit Conversions
The SI unit of energy is the joule, but real-world applications use many different units. Electricity is measured in kWh, food energy in kilocalories (kcal), heating in BTU, and atomic physics uses electron volts (eV). This converter handles all of them, from the tiny eV (1.6 × 10⁻¹⁹ J) to gigajoules.
Power Unit Conversions
Watts and kilowatts dominate electrical measurements, but horsepower still reigns for engines and motors. HVAC systems use BTU/hr, and large-scale power generation uses megawatts and gigawatts. Switch to Power mode to convert between all these units instantly.
Practical Applications
Use this converter to compare electricity costs across regions (kWh pricing), understand car engine specifications (horsepower to kilowatts), evaluate HVAC system capacity (BTU/hr), or calculate solar panel output. The quick reference section provides common real-world energy and power values for context.
Related Tools
Calculate your electricity costs with the Electricity Cost Calculator. Convert temperatures with the Temperature Converter. For other measurement conversions, try the Unit Converter.