Where does your energy come from? Analyzing your energy bill

Mary Savina
Carleton College
Author Profile
This material was originally developed as part of the Carleton College Teaching Activity Collection
through its collaboration with the SERC Pedagogic Service.
Initial Publication Date: September 15, 2010 | Reviewed: July 6, 2017


Armed with utility bills (or conversations with relatives) and information from utility and government websites, students trace the sources of their electricity, heating and cooling, and other components of their energy use. Data on energy sources from different states and countries (represented by the students' households-of-origin) form the basis for discussions about energy sources, including their environmental, societal and economic advantages and disadvantages.

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Learning Goals

  • Analyzing energy use data, including making conversion among units, and developing comparisons for different sources (quantitative skills).
  • Calculating personal contribution to the energy expenditures of humans.
  • Researching on-line and written documentation from government and utility sources.
  • Summarizing and synthesizing the societal, economic and environmental costs and benefits of energy use.

Context for Use

I use this exercise in introductory geology (and introductory environmental geology) classes at Carleton College. Typical class size ranges from 18 to 48. This exercise comes near the beginning of a unit on energy, whose other components include reading, debates, a lab exercise on nuclear waste disposal, and drafting of an ideal energy policy.

At the start of the course, I ask students to contact their families to get a copy of a recent energy bill. Most are able to do so within several weeks; this exercise itself comes about seven weeks into the trimester.

Typical geology classes at Carleton include students from a dozen or more states and at least a few foreign countries. This variety gives a good range of different energy mixes, including various percents of oil, gas, coal, nuclear, hydro, geothermal, wind and others. However, the exercise can be adapted to classes with a narrower range of utilities.

I have students use the results of their research in two main ways:
Class discussions that culminate in each student writing a short essay that's evaluated as part of the course work (the teaching materials linked from this page assume this model) OR
as part of a larger project on hometown environmental health. In this case, energy sources and uses are part of a series of topics (also including drinking water sources, watershed/water bodies, pollution and waste, natural hazards, and cancer rates) that students explore throughout the trimester and then write about as the course final exam. Here's part of that prompt:
During the exam period, you will write the text that tells the story of the environmental health of your hometown. The tables, graphs and maps, all captioned, will be the illustrations for this story.

Description and Teaching Materials

These teaching materials assume that the energy exercise is a stand-alone part of the energy unit in the course, not necessarily linked to a term-long project.

Teaching Notes and Tips

While students do calculate and write individually about the total energy used by their household, they share mainly the information about cost per kwh, BTU or whatever units the utility uses and the utility's energy sources. These data go into a spreadsheet that's available to the students as they write their summaries.

A common source of confusion comes from the variety of energy sources used for electricity, heating and cooling. Some students will come from households where climate control - as well as lights, etc. - are all-electric. Others will have energy bills that are split between electric units (such as KWH) and thermal units (such as BTU). One can convert among these units (1 kwh = 3412.14 BTU according to http://www.aps.org/policy/reports/popa-reports/energy/units.cfm; an American Physical Society site with an excellent discussion of energy units). You may want to ask students to convert everything to kwh, likely to be the standard reporting of electricity (more quantitative skill building!).

Once students have worked with some of the data long enough to know the cost of electricity per kwh, I have them line up in order of that cost. This part of the exercise helps show students the wide variation within the U.S. in the cost of electricity from state to state. We can then explore some of the reasons, historical and otherwise, for these variations.


For a stand-alone assignment (students get this information in the syllabus and it applies to all written work):
I expect that your papers and other written work will be typed or printed and that spelling and grammar will be perfect. When reading written work, I look for well-defined questions, good understanding of the subject, careful and complete observations of geologic processes, sound logic connecting the observations to the conclusions, clearly stated conclusions and complete discussion of the implications of the conclusions. All sources of information, including web sites, should be cited completely, using the geology style of citation described in the next section.

As part of a final exam:
The best projects will show that you've researched the questions in detail (not all questions are applicable to each area, and not all questions need to be responded to at the same depth). Your interpretations, as illustrated by your captions and your writing, should draw the connections among different sources and between topics, where possible. Your writing and use of graphs, diagrams, and maps should show your facility at using quantitative information and numbers in making arguments. In many cases, you'll need to determine the relative importance of some numbers that may look little or large, when they are presented without context.

References and Resources

These three Department of Energy sites provide a ranking of states by energy production and use, a breakdown of energy use and locations of the major power plants, as well as emissions data.

These are two carbon footprint calculators, one from carbonfund.org and the other from the EPA. Once students have deciphered their utility bills, calculating their carbon footprint is relatively simple.

American Physical Society site describes the ways energy is measured and the conversions among these measurements.

Steve Semken (Arizona State University) concept map exercise on electricity sources. This exercise could be used as a preamble to the energy bill analysis.

Other suggested activities and resources for incorporating energy-related topics in geoscience classrooms. Several of these would work well in economics classes and in other subject-matter settings.