Efficiency

• Less energy wasted = more efficient transfer
• Efficiency = useful output energy transfer / total input energy transfer
• Efficiency = useful power output / total power input
• Non renewable - will run out, damage environment, provide most energy

  eg. Coal, oil, gas, fossil fuels
• Renewable - never run out, can be unreliable and not much energy eg. Solar, geothermal, biofuels, hydroelectric