Energy Habits: Home Energy Audit

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Objective

SWBAT read electric and heating bills, and make equivalences between the two.

Big Idea

This lesson lays down the basics for a home energy audit.

Getting Started

This lesson lays down the basics for a home energy audit. Since the audit involves the students researching their own personal energy use, they will need ask their parents for access to potentially sensitive personal information. 

 One way for them to obtain  their energy data is to log on to the website of their energy provider and download a copy of their bill. Ideally they should have a set of data going back 12 months so that they can compare usage.

You will need only part of one class to introduce this lesson from the Engage portion. Think about introducing this 2-3 days ahead of the audit. Day "two" will consist of working with the energy bills. 

Materials Needed: heating, electric bills

Technology Tools Used: none

Useful Vocabulary: therm, Btu

Engage

10 minutes

I start with the Home Energy Audit handout. The first part of this lesson explains what we need to gather to get started, and that we need their parents' permission to make progress. Any student whose parents don’t want them to use their own data can use some sample data that the teacher provides.

Home Energy Audit - Introduction

Use the following directions to explain the project to your students. Answer any questions they may have and send them home with the parent permission form. 

We have explored the concept of energy use, now we will try to quantify the ways in which we use energy directly.

This is a much simpler question that finding the embodied energy in the products we use, so getting the answers we want should be a snap! The exciting part about this project is that once we’ve assessed our energy use, we’ll actually have the information and the power we need to make change. It’s simple to take control of our house!

Big questions for this project are:

  • How much electrical energy do we use?
  • How much energy do we use for heat?
  • How much energy do we use for transport?
  • How much carbon do we emit into the atmosphere due to our direct consumption of energy?

The first step toward answering these questions is to gather the data on our energy use. We will therefore gather the following primary documents, from which we will extract the information we need:

  1. Electric bill: this can be a paper copy or looked up on-line, if you have paperless billing.
  2. Heating bill
    • if you heat with gas: you can look at your gas bill or get 12 months of use data on-line
    • if you heat with oil: this is a bit trickier, if you don’t have records you may have to call the oil company to find out how much you’ve been using.
    • if you heat with electricity: you are all set, since your heat is rolled into your electric bill!
  3. Mileage: no documents to gather here, but we can estimate or measure it directly by checking your cars’ odometers.

After we have the necessary documents, we can learn how to read the information there and use our powers of unit manipulation and conversion to assess the data.

Day 2: Explore

30 minutes

Once the students have gathered their bills and permission slips, we can proceed to the meat of the lesson. By now they should have the unit conversion skills they need to learn the new necessary units quickly; the therm and the Btu, which are used for measuring gas. I deliver a lecture on those units, and I walk through the structure of the bills with sample bills projected on the board. Then I turn them loose on the Home Energy Audit - reading electric and gas bills worksheet. 

Circulate while they work. Many students will get hung up converting from power to energy or the other way around. This is another opportunity to teach that material, and to work with those who still need help converting units. 

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This will be a very practical lesson on how to read your bills and determine how much energy you use. There will be some unit conversion to do. If you get stuck on that, do refer to previous handouts on the manipulation and conversion of units.

1. Electric Bill

This will be a very practical lesson on how to read your bills and determine how much energy you use. There will be some unit conversion to do. If you get stuck on that, do refer to previous handouts on the manipulation and conversion of units.

 

1. Electric Bill

We’ll tackle the electric bill first, because it is by far the easiest. Do the following:

Find the bar graph labeled “Electricity Use.”

  1. What does the x-axis tell you?
  2. What is shown on the y-axis?
  3. What was your total electricity use for the current month in kWh?
  4. What is the current delivery charge in kWh?
  5. How many kilowatt-hours of electricity were used in November? in July?
  6. How many kilowatt-hours of electricity were used in the whole previous year?
  7. What is the mean monthly electricity use over the year?
  8. In which month did you use the most electricity? the least?
  9. What might explain these differences?

 

2. Gas Bill

The gas bill is an odd duck. We need to learn a new unit to analyze it, the therm. The therm is approximately the energy released by burning 100 cubic feet of natural gas, and is officially defined as 1 therm = 100000 Btu. This raises the question...what is a Btu? It is a British thermal unit, which is defined as the amount of energy needed to heat 1 pound of water from 39 F to 40 F. Weird. Ok, trivia aside, the important fact to know is that 1 Btu = 1055 J.  To summarize:

1 therm = 100000 Btu = 105,500,000 J

1 Btu = 1055 J

  • What is 1 therm in J? in kWh?

1 hr = 3600 seconds

1kW - 1000W

105,500,000 J / 3600 seconds = 29305.5 W/1000 = 29.3 kWh

  • Find the portion of the bill labeled “Gas Use History”.
    1. What does the x-axis tell you?
    2. What is shown on the y-axis?
    3. What was your total gas use for the current month in therms?
    4. What is the current delivery charge per therm?
    5. How many therms did you use in November? in July?
    6. How many therms did you use for the entire year?\
    7. What is this number in J?
    8. In which month did you use the most gas? the least?What might explain these differences?
    9. What is the mean monthly gas use over the year?

Explain

15 minutes

I close with a discussion about where student think the energy usage in their home is; what do students think is the best way to save energy now that they’ve made a preliminary examination of their bills? Open this up to discussion.

The attached article is a great follow up to have  students read and then reflect on their home energy use. 

 In the video below where my students reflects on how using real data helped her make sense of her home energy use and gave her ideas on energy conservation for her family.


Evaluate

10 minutes

I evaluate as I circulate. It’s pretty easy to tell whether they’ve correctly read the bill. That’s the important point here. If they can’t figure out some of the tougher questions, I urge them to move on.   My goal is for students to  begin to see patterns in energy use over the course of a year and connect that to  seasonal fluctuation and home heating and cooling as well as laying the foundation for thinking about use of household electronics, appliances, and other devices that use energy.