Energy efficiency

• Input energy


  The energy supplied to an appliance
• Useful output energy


  The useful energy transferred by the appliance
• Efficiency


  The percentage of input energy transferred to useful output energy
• The higher the percentage of energy that is transferred usefully, the more efficient an appliance is
• Calculating energy efficiency


  Use equation: efficiency = (useful output energy / total input energy) x 100%
• The efficiency can never be more than 100%
• You can never get more energy out of a device than you put in
• Efficiency measurement


  Efficiency is measured in percentage
• A device can never be more than 100% efficient
• Types of energy


  • chemical
  • elastic
  • electric
  • kinetic
  • light
  • sound
• To calculate the efficiency of a device you have to identify the input and the useful output energy transferred
• Sometimes it is harder to identify the energy input and useful output energy
• Lightbulb comparison


  • Filament lightbulb
  • LED lightbulb
• Filament lightbulb transfers 4 J as light
• LED light bulb transfers 68 J as light