Understanding Energy Units
SI Units
- Joule (J):
- SI unit of energy
- One newton-meter of work
- Energy to lift 102g by 1 meter
- Prefixes:
- Kilojoule (kJ) = 1000 J
- Megajoule (MJ) = 1000 kJ
- Gigajoule (GJ) = 1000 MJ
Electrical Energy
- Watt-hour (Wh):
- Common for electrical billing
- 1 Wh = 3600 J
- Household use measured in kWh
- Applications:
- Utility bills
- Battery capacity
- Power consumption
Heat Energy
- Calorie (cal):
- Heat to raise 1g water by 1°C
- Food energy in kcal
- 1 kcal = 4.184 kJ
- BTU:
- Common in HVAC systems
- Heat to raise 1 lb water by 1°F
- Used in air conditioning ratings