Power and Energy in the Home

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Screen shot of applet for Power and Energy in the HomeThis lesson is designed to allow middle-school students (and others) to explore power and energy usage in the home. Power comes from a power plant to your home through a system of power lines, power substations, and transformers that make up the power grid. This Java applet shows power flowing through the transformer drum, the meter, and into the home circuit breaker panel. From there, it powers various appliances. Users can open and close switches to turn appliances on and off and track power usage and learn concepts such as power conservation, network flows, and the relationship between power and energy. An appliance's energy use and cost depend both on the amount of power needed for its use and on the amount of time the appliance is used. Some appliances require a lot of power, but we don't use them often, so they don't use much energy over time. Other appliances may not need as much power, but are used for more time. For example, a toaster needs a lot more power than a room air conditioner does, but most people use a toaster for much less time.


  1. Set the blue switches so that only the Energy Star refrigerator ('E-Star Fridge' under Kitchen Appliances) is on. What is the Current power consumed? (It's the green number near the bottom of the pole.) Compare the Energy Star refrigerator with the standard refrigerator. About how much more power does the standard refrigerator use?
  2. If your XBOX 360 and 40" LCD TV are on for 10 hours, how much energy is used?
  3. Set the blue switches so that only the toaster is on. What is the Current power consumed? Click on the Pause Time, Reset Time, and then Start Time buttons. You should see the energy use and energy cost change on the kWh meter. You should also see the Elapsed Time total changing near the bottom of the screen. If you use the toaster for 10 minutes, how much energy do you use? When the cost is 10¢ per kWh, how much do you pay to use the toaster for ten minutes?
  4. Set the switches so that only the Solar Module (scroll down under Household Appliance) is connected. What happens? Switch on the LCD TV. Now what happens? Which appliances need less power than the solar module can supply? If there were twenty of these solar modules producing electricity, how much power could they supply?
  5. Energy is sold by the kilowatt hour (kWh). A kilowatt is 1,000 watts. If you use the 1,000-watt hair dryer for one hour, you use 1 kWh (one kilowatt hour) of energy. How much energy is used if you dry your hair for 15 minutes?
  6. Click on the Show plot button. You should see the graph of Power Consumed Over Time. Change the appliances and click Reset Time to start the time over. How does the graph change as you change appliances and open and close the various switches?

Resources for Students & Teachers

  • Quick-Start Guide: Use this quick-start guide to learn about the features of this applet.
  • Lessons: Lessons have been created to help you use this applet in your classroom.