Lesson Overview

Students will learn how to measure their electricity consumption and calculate a monthly electricity bill. Projected savings will be assessed from various energy efficiency and conservation measures.

Target Grades: 9-12

Set Up Time: 20 minutes

Class Time: 1.5-2 hours

Lesson Resources

Objectives

  1. Estimate household electricity consumption.
  2. Measure and compare the different amounts of electricity used by appliances and devices.
  3. Explain and implement ways to conserve electricity.

Guiding question: How do I know how much electricity something uses?

Educational Standards

ALASKA CULTURAL STANDARDS: B4

ALASKA ENGLISH LANGUAGE ARTS: 9-12 WSLST.PDW.4

ALASKA MATHEMATICS STANDARDS: HS.N-Q.1.; HS.S-IC.5; HS.N-Q.2; HS.S-IC.6; HS.S-IC.3.

ALASKA DIGITAL LITERACY STANDARDS: 6-12.EL.4, 6-12.CT.2

ENERGY LITERACY CONCEPTS: 6.2, 6.6, 6.8

NGSS: HS-ESS3-2

Lesson preparation:
  • Research electricity rates in your community.
  • Read the Background information below.
  • Download the Personal Electricity Consumption spreadsheet file (from “Lesson Resources” dropdown above) and make it easily accessible for each student to use.
Materials:
  • One computer with internet access per student.
  • Optional: 1 to 5 Kill a Watt meters or other electricity monitors

Most of us do not think about how much electricity we actually use. We flip a switch and the lights turn on, or we press a button and the TV or computer turns on. However, every flip of a switch or press of a button means we are (1) using electricity and (2) spending money. Understanding how much energy these appliances use and how much they cost to run each day is valuable and can help facilitate more responsible behavior through conserving energy or using more efficient appliances. Most Alaskans’ energy also comes from non-renewable resources and cause emissions. 

In 2016, the U.S. Energy Information Administration reported that the average American household uses 897 kilowatt-hours (kWh) of electricity a month. Homes and commercial buildings consume 71% of the electricity in the United States and this number is expected to rise to 75% by 2025 (NREL). Existing residential buildings represent an extremely large source of potential energy savings. According to the Alaska Energy Authority’s 2012 End Use Study, residential electricity consumption is quite significant. Major appliances such as refrigerators, freezers, washers, and dryers consume 24% of the electrical energy in households in the Railbelt and Southeast Alaska and consume 35% of the electrical energy in households in Bethel.  Appliances such as TVs and microwaves continue to draw power even when switched off. Eliminating these phantom loads by unplugging them and turning off appliances like lights, computers, and TVs when not in use are all ways to realize energy savings. To identify areas for efficiency and conservation, and therefore reduced emissions and cost savings, we must first measure our energy consumption.

There are multiple methods to measure personal, household, or school energy consumption, including using energy bills, energy monitoring tools (like a Kill a Watt meter), and conducting online energy audits. While energy bills allow a homeowner to keep track of how much energy is used from month to month, they do not indicate how much energy specific appliances or devices use. A Kill A Watt meter measures the electricity used in a given outlet by a given appliance or device. For example, you can plug a refrigerator or computer into a Kill A Watt meter (which is, in turn, plugged into a wall socket) and measure the amount of energy the device uses over an hour, day or a week. Kill A Watt meters are a great way to closely monitor how much energy individual devices and appliances use. However, if you do not have a Kill A Watt meter, there are several online tools for estimating your home’s electricity consumption based on the total number of household devices and appliances in your home. 

Gauging your energy use off of your electric utility bill gives you a starting place, or baseline, from which to begin your investigation. Measuring consumption of specific appliances with a Kill A Watt meter helps identify energy hogs and lets you know when certain appliances start using energy inefficiently. From this baseline you can begin to identify areas and appliances in your home where you can apply conservation and efficiency measures in order to save energy and money. Knowing your energy consumption level can help you be aware of your personal emissions, the impacts those have on the environment, and how you can reduce those impacts. You can also get a professional energy audit which can also give you recommendations on how to reduce your energy use.

The cost for energy varies across Alaska. Each utility sets its rates for services, and for electricity that is charged per kilowatt hour plus flat fees. Non-electric heating may be charged per ccf (natural gas) or per gallon (heating oil, diesel, propane, etc). With electricity, the state offers Power Cost Equalization (PCE) for communities that have a very high rate of electricity (three to five times that of more urban areas of the state). The state reimburses utilities for usage by consumers up to 500 kWh per month. The way that works for consumers is that they pay a certain rate up to 500 kWh per month, then a higher rate over 500 kWh per month, depending on the cost to the utility. 

Once you know what how much energy you consume and how much it costs you to use different appliances, you can start reducing your energy consumption through conservation and efficiency. Identify phantom loads, appliances or lights that are left on, inefficient lights or appliances, and other “energy hogs” through an energy assessment (or pay somebody to do a full energy audit), then make a plan to reduce your energy use. This lesson helps with electricity consumption, and links with top tips for reducing energy consumption can be found in the Additional Resources section of the lesson.

 

Consumption: Using a resource, referred generally in this lesson as electricity usage. 

Energy Audit: An evaluation of energy consumption in a home, business, or public building to determine how energy can be conserved or used more efficiently. 

Energy Conservation:Energy conservation is a behavior change that results in not using energy at a time when one normally might. For example, riding a bike instead of driving a car, unplugging computers and other electronics at night or when not in use, or turning off the lights when you leave a room.

Energy Efficiency:Energy efficiency is using improved technology that makes an existing use of energy more efficient; i.e., allows us to do more with less. For example, replacing incandescent light bulbs with light emitting diode bulbs (LEDs), adding extra insulation to a house, or using Energy Star® appliances that have special power-saving measures installed.

Kilowatt-Hour (kWh):  A unit used to measure electrical energy, and used by utilities to measure monthly energy use. A kilowatt-hour is the amount of energy used if you use 1000 watts for one hour and is equivalent to 3.6 million joules or 3,412 BTUs. 1 kilowatt-hour (kWh) = 1000 watts x 1 hour = 100 watts x 10 hours

Phantom Load: Electricity consumed by an electronic device or appliance while it is turned off or in standby mode. This includes electricity used to power a clock on a microwave or a small light indicating that a computer is sleeping.

Power Cost Equalization: Run by the Alaska Energy Authority, the Power Cost Equalization Program provides economic assistance to Alaskan communities and residents of rural electric utilities where the cost of electricity can be three to five times higher than for customers in more urban areas of the state. The program’s purpose is to equalize power costs to near the average cost of power in Anchorage, Fairbanks, and Juneau. Residential and community facility buildings in nearly 200 communities are eligible for the reduced rate. Consumers in eligible communities pay a certain rate up to 500 kWh per month, then a higher rate over 500 kWh per month, depending on the cost to the utility.

Watt: A watt is a basic unit of electrical power which measures the rate at which electricity is used. watt = joules per second

Gear Up: 
  • Start with a discussion about how students use electricity every day, perhaps making a list of as many things as they can think of, and writing them on a white or Smart board. Then, ask students why their family or parents care how much electricity they use and guide them to think about cost of electricity.
  • Ask students how electricity is measured. Next, ask students why it is important to know and understand personal and household energy habits. Guide the conversation based on the background information.
Activity
  • Each student should have a computer, lap top, or tablet with the Personal Electricity Consumption Worksheet downloaded on it. If you don’t have access to Microsoft Excel, you can still download the worksheet and upload it to Google Drive or other file sharing service without opening it. If your school/district use Gsuite, the file can then be shared with your students. a class, identify the different types of waste produced in your community (using the vocabulary list and any others that constitute a significant portion of your community’s waste).
  • Students list all of the lights, devices and appliances in her/his house that use electricity and record them on the Personal Electricity Consumption Worksheet. They can either do this from memory or take a print out of the sheet home and complete it there to ensure the have an accurate list.
  • Once the students have listed the appliances and devices, visit: https://generatorist.com/power-consumption-of-household-appliances. There they can search for an item and get an estimated wattage that they use to enter into the worksheet. Students can also do this list at home and use a Kill a Watt meter to get an accurate wattage, use label information, or use the same link to find wattage information.
  • Next, the students enter into the spreadsheet an estimated number of hours per day and days per month that they use the appliance. The spreadsheet will calculate the kW and kWh that are used for each device each month. 
  • Each student then enters their local electric rate(s) into cells C12 and E12. A table is provided for some rates, however using a current rate will be the most accurate. If possible, show students a local electric bill (with identifying information removed).
  • The worksheet will automatically total the kilowatt hours (kWh) for the month and will calculate the associated electric bill based on the rate of the value in your local electric rate. If the kWh are less than 500, it uses the rate in C12, and if the kWh is more than 500, it uses C12 for the first 500kWh and E12 for everything over 500kWh. For some communities, this is the same rate, however for those with PCE, electricity rates are much higher after 500kWh. Discuss PCE with students and how all energy costs, not just electricity, vary across the state. 
  • Once students have filled out the worksheet, facilitate a discussion to analyze and summarize what the students found out about their personal energy consumption. Some sample questions are:
    • Which of your devices uses the most power?
    • What does the spreadsheet calculate?
    • How might you conserve energy or use energy more efficiently?
    • What have you learned about your personal consumption of energy that surprised you?
  • Wrap up:
    • Ask students to identify ways that they can reduce their energy use through efficiency and/or conservation, and pledge to make at least one of those changes.
Extensions
  • Conduct a classroom or school-wide electricity assessment.
    • Have students predict which items will use the most electricity. Decide on at least five devices to measure.
    • Plug each device into a Kill A Watt meter or other electricity monitor for a day or more and record the kWh each device uses, instead of measuring the instantaneous power (watts). This is especially helpful for items that do not use a consistent amount of watts (such as refrigerators) or are used a variable amount of time each day (such as a projector). At the end of the week, calculate how much energy just those five devices/appliances use per month. Estimate usage for other appliances based on label information or online searches, and estimated hours of use.
    • If possible, get the electric bill for your school and see how it compares to a home energy bill. (Usually the principal can request a school’s electric bill from a facility manager.)
    • After data collection, students can choose how to represent their data. Discuss whether to use a table, graph, or both, and why.
    • Students then analyze and interpret the results. Lead a discussion on what they would do differently if they were to conduct this experiment again and what questions arose from the experiments that could be further investigated.
    • Have the students discuss ways that the school, individual classrooms, and students can conserve energy and be more energy efficient. 
  • Complete an energy assessment checklist which looks at electricity, heating, and water usage. The Home Energy Assessment page is geared towards adults but can be used with high schoolers too and includes options for a basic checklist or deeper analysis.
  • Ask students to make an energy conservation and/or efficiency power pledge. If possible and available, students get a copy of the electricity bill from their parents and record the energy usage for their home. They will use this as a baseline.
    • Then students should take actions to conserve energy and compare their electricity use until the next energy bill. 
    • If possible they should engage their household to take part in this energy conservation action plan as well. Keep in mind that many things can impact energy use. Different temperature, number of occupants, a family visit during that month, etc. If students do not see a reduction in their energy use, it could be many factors and not just their energy consumption.
Evaluation
  • Students complete the spreadsheet with at least five items and can explain what uses electricity in their house.
  • Students can explain how to reduce their personal electricity usage.