Convert between energy units
A calorie (small 'c') is the energy to raise 1 gram of water by 1°C. A Calorie (capital 'C') or kilocalorie (kcal) equals 1,000 small calories. Food labels use Calories (kcal). 1 Calorie = 4.184 kilojoules.
A watt is one joule per second (W = J/s). Watts measure power (rate of energy transfer), while joules measure total energy. A 100W bulb running for 1 hour uses 360,000 joules or 0.1 kilowatt-hours of energy.
BTU (British Thermal Unit) is the energy to raise 1 pound of water by 1°F. It's commonly used for heating/cooling systems, air conditioners, and fuel energy content in the US. 1 BTU ≈ 1,055 joules.
1 kWh = 3.6 million joules (3.6 MJ). Multiply kWh by 3,600,000 to get joules. Conversely, divide joules by 3,600,000 to get kWh. Electricity bills use kWh as it's more practical for household consumption.
Food energy is measured in kilocalories (kcal) or Calories (with capital C) in the US, and kilojoules (kJ) in many other countries. 1 kcal = 4.184 kJ. Average adult needs about 2,000 kcal (8,400 kJ) daily.
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