Know Your Energy Costs

Grade Level: 6-12

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Source: National Energy Education Development Project. Adapted with permission.

It takes energy to run the appliances and machines we use everyday. The national average commercial cost to use this energy is $0.10/kilowatt hour. 

In addition to the financial cost, there is also an environmental cost in the form of carbon emissions. The general rule of thumb is that every kilowatt-hour of electricity produces 1.6 pounds of carbon dioxide. Some sources don’t emit carbon dioxide, but more than 70 percent of our electricity is produced by fossil fuels. Fossil fuels play an important role in allowing us to have lifestyles we’re accustomed to, but they do emit carbon dioxide, and we all want to be good stewards of our resources. 

The goal of this activity is to become aware of how much energy you use at school — and the financial and environmental costs.

Materials

Procedure

  1. Make a list of the appliances or electronic devices used at school. Set up a table like the one provided here.

  2. Learn to read an electric nameplate. Find the current (measured in amperes, A) and voltage (V). Some nameplates may also include the wattage (W). If the wattage is not listed, calculate it with this formula: W = V x A.

  3. Conduct an energy survey by finding the wattage for each object using information on electric nameplates. If you have access to a “Kill A Watt” meter, measure wattage using this tool. Or find the average wattage online. Many utility companies list estimates on their websites.

  4. Calculate the economic and environmental cost of using each appliance during the school year.

    5. Use these formulas to find the values needed:

    Yearly Use = hours used/week x weeks used/year = hours/year.

    One kilowatt is equal to 1,000 watts. To find kilowatts, divide by 1000 (kW = W/1000).

    Yearly Cost = Hours Used x Kilowatts x Cost of Electricity (kWh).

    CO2 a year = W x hours/year x rate of CO2/kWh.

  5. Discuss your findings. Brainstorm with your classmates  ways that energy could be used more efficiently or how it can be conserved. 

    6. Sample Table:

    Device or Appliance

    Watt
    W

    Kilowatts
    kW

    Hours/ Week

    Hours/ Year

    Rate
    $/kWh

    Yearly Cost

    CO2/ kWh
    Lbs

    CO2/year
    lbs

     

     

     

     

     

    $0.10

     

    1.6

     

     

     

     

     

     

    $0.10

     

    1.6

     

     

     

     

     

     

    $0.10

     

    1.6

     

     

     

     

     

     

    $0.10

     

    1.6