Energy Efficiency worksheet

  1. What is the energy efficiency formula?
  1. An elevator has an energy efficiency of 64%. What amount of energy must the elevator consume in order to provide 95 kWh of useful energy?
  1. A microwave consumes 27 000 J of energy in order to provide 21 500 J of useful energy. What is its energy efficiency?
  1. A computer that is 87% efficient consumes 375 kWh of energy. How much useful energy does it provide?
  1. A television that is 83% efficient provides 4 600 J of useful energy. How much energy does it consume?
  1. An oven consumes 425 kWh of energy in order to provide 386 kWh of useful energy. What is its percent efficiency?
  1. A DVD player that is 79% efficient consumes 9 500 J of energy. How much useful energy does it provide?
  1. An iPod that is 35% efficient provides 16 kWh of useful energy. How much energy does it consume?
  1. An electric lawn mower consumes 35 000 J of energy in order provide 12 600 J of useful energy. What is its percent efficiency?
  1. A hairdryer that is 42% efficient consumes 143 kWh of energy. How much useful energy does it provide?
  2. A kettle that is 85% efficient provides 16 700 J of useful energy. How much energy does it consume?
  1. A vacuum cleaner consumes 750 kWh of energy in order to provide 583 kWh of useful energy. What is its percent efficiency?
  1. An electric razor that is 56% efficient consumes 5 800 J of energy. How much useful energy does it provide?
  1. A toaster that is 37% efficient provides 109 kWh of useful energy. How much energy does it consume?
  1. A lamp that is 89 % efficient consumes 14 kWh of energy. How much useful energy does it provide?
  1. A cell phone that is 43% efficient provides 6 300 J of useful energy. How much energy does it consume?
  1. A radio that is 72% efficient consumes 385 J of energy. How much useful energy does it provide?
  1. Explain the difference between a light bulb that is 75% efficient versus one that is 97% energy efficient.
  1. The table below has three different hairdryer models. Which is most energy efficient?

Model A / Model B / Model C
Useful energy / 450 kWh / 700 kWh / 600 kWh
Energy consumed / 520 kWh / 770 kWh / 630 kWh
  1. What could be a reason that consumers buy products that are less energy efficient?