What Electric Bills Can Tell You About Energy Use
AbstractThis project is a great way to "bring home" the concept of energy use. All you need to get started is a good-sized sample of monthly electric bills from households in your area. Building from this simple beginning, you can ask questions that can take you in many different directions. For example: How much electricity does the "average" person in your area use per month? How much does electricity use vary among different families?
Andrew Olson, Ph.D., Science Buddies
SourcesThis project is based on:
- O'Brien, Jr., W.P., 2007. "Mining Power and Hydrocarbon Consciousness from the Monthly Electricity Bill: A Classroom Project," Physics Education 42(1, January): 81–87.
The goal of this project is to estimate consequences from household electricity use using data from a survey of electric bills combined with information about electricity production.
You might not think that a monthly electric bill would be terribly interesting. However, if you collect a stack of them from different households, you'll find that you can do some very interesting analysis of the numbers.
You'll be able to see how much electricity the "average" person uses per month. Perhaps more importantly, you'll be able to see the amount of variation in usage of electricity from one household to another. To learn more about electricity, see the Science Buddies Electricity, Magnetism, & Electromagnetism Tutorial.
You can also do some calculations to find out about the costs of using electricity. Not only in terms of dollars and cents, but also in terms of resources consumed, or carbon dioxide produced. This project is a great way to start thinking about the importance of energy efficiency and energy conservation.
Terms and Concepts
To do this project, you should do research that enables you to understand the following terms and concepts:
- kilowatt (kW)
- kilowatt-hour (kWh)
- Energy use rate
- Power load
- in money terms (cents/kWh)
- in coal equivalents (kg/month or kg/year)
- in carbon dioxide emissions (kg/month or kg/year)
- What is the breakdown of sources for electricity production in the U.S.? In your state?
- How efficient are electric power generation facilities?
- How much carbon dioxide is produced, on average, per kWh of electricity for a coal-fired plant? Natural gas? Nuclear? Wind power? Hydroelectric power?
- How much power can a single wind turbine produce, on average? How many wind turbines would be required to replace a single "average" coal-fired plant?
- Official energy statistics are available from the U.S. Energy Information Administration. Retrieved August 13, 2020.
Here is an Excel tutorial to get you started using a spreadsheet program:
Excel Easy. (n.d.). Excel Easy, #1 Excel tutorial on the net. Retrieved June 11, 2014.
Because energy use patterns can vary greatly from one family to another, a home energy audit can help you identify what you can do to save energy around your house. If you're interested in doing a home energy audit, this website can take you through the process:
LBNL, (n.d.). The Home Energy Saver. Lawrence Berkeley National Laboratory. Retrieved August 13, 2020.
This project is based on:
O'Brien, Jr., W.P., 2007. "Mining Power and Hydrocarbon Consciousness from the Monthly Electricity Bill: A Classroom Project," Physics Education 42 (1, January): 81–87.
Materials and Equipment
To do this experiment you will need the following materials and equipment:
- Computer with Internet connection and printer
- Sample monthly electrical bill from at least 30 different households (more is better), along with the number of people living in the house
- Optional: spreadsheet program (like Microsoft Excel or WordPerfect QuattroPro
- Do your background research so that you are knowledgeable about the terms, concepts, and questions, above.
Collect monthly electric bills (ideally from the same month) for at least 30 different households.
- Make sure to find out how many people live in each household. Have the participants write the number of household members down on the bill.
- To maintain privacy, the participants can black out (or cut off) identifying information such as name, address, and account number.
- The more households you can include in your sample, the better. See the Science Buddies How-To resource Sample Size: How Many Survey Participants Do I Need?
Here are some ideas for getting volunteers to participate:
- Start early on this part of the project, because it will take time to gather a large sample of bills.
- Ask your friends, relatives, and classmates.
- Make a one-page flyer describing your project and your need for monthly electric bills. Make sure that your flyer reminds people to write down the number of people in the household, and lets them know that they can remove their name, address and account number from the bill. Get permission to post your flyer at one or more local businesses with a lot of foot traffic. Leave a collection box or envelope for utility bills.
- See if you can get a neighborhood newspaper interested in writing an article about your project. Readers could send their bills to the newspaper office for you to pick up.
- Once you have the bills in hand, it's time to start analyzing them. You can do this by hand with a calculator, or you can use a spreadsheet program (like Microsoft Excel or WordPerfect QuattroPro).
You may think of more calculations to make with the data as you go along, but the table has some suggested statistics to compute to get you off to a great start:
Quantity Range Mean Median Standard Deviation kWh/household-month $/household-month persons/household kWh/person-month $/person-month cents/kWh W/person
Here is an explanation of each of the quantities in the table:
- Kilowatt-hours per household per month (kWh/household-month): electric use is measured in kilowatt-hours (kWh).
- Dollars per household per month ($/household-month): the total dollar amount for electricity use for the month for each household.
- Persons per household (persons/household): this number should be supplied on each bill. If the number is missing, don't use that particular bill.
- Kilowatt-hours per person per month (kWh/person-month): for each bill, divide the total kilowatt-hours by the number of people in the household.
- Dollars per person per month ($/person-month): for each bill, divide the total dollar amount for electricity by the number of people in the household.
- Cents per kilowatt-hour (cents/kWh): for each bill, divide the dollar amount for electricity by the number of kilowatt-hours, then multiply by 100 to convert from dollars to cents.
- Watts per person (W/person): for each bill, divide the number of kilowatt-hours
For each quantity in the table, calculate the range, the mean, the median, and (for advanced students) the standard deviation. Start by entering the raw data for each quantity in a separate column in a spreadsheet (or raw data table).
- Spreadsheet programs will have all of these functions available so that you can create formulas to make the calculations automatically.
- If you need help with using a spreadsheet program, try this tutorial http://www.excel-easy.com/.
- See the Variations section for presentation ideas on how to make these numbers more meaningful.
Ask an Expert
This project explores topics key to Responsible Consumption and Production: Ensure sustainable consumption and production patterns.
Here are some ideas for taking the project further:
Investigate other environmental consequences of electric generation. For example:
- Burning coal produces about 1 kg of CO2 per kilowatt-hour of electricity produced (plus other pollutants). (O'Brien, 2007) Figure out how much CO2 this amounts to per person for the "average" electricity user in your study.
- Heat-driven electric generation (e.g., coal, natural gas, nuclear) has only about 30–35% efficiency overall, which is roughly half of the theoretical maximum efficiency (Second Law of Thermodynamics) of 64%. (O'Brien, 2007; EIA, 2007b) Coal has a heat energy of 6.6 kWh/kg, but because of the 30–35% efficiency of the electric generation process, only 2.2 kWh of electricity is produced per kg of coal. Figure out much coal is required per person per year for the "average" electricity user in your study.
To give some life to your numbers, think of equivalent measures for per-person power consumption. (O'Brien, 2007) For example:
- You could figure out how many 60-watt light bulbs could be powered by one person's average monthly electric usage.
- You could figure out the equivalent horsepower for a person's monthly electric usage.
- You could figure out how much sunlight (in terms of area at the Earth's surface) would be required to provide one person's electric power consumption (using currently available solar electricity technology).
- Learn about the mix of generation sources that produce electricity in your state. How much of the capacity is from renewable sources? What fraction of the generation capacity could realistically come from renewable sources in the future? (EIA, 2005b; for states other than California, substitute the desired state name for 'california' in the link text)
- Advanced. Investigate the differences in per person energy costs that you can identify in your study. Do some families have a more energy-efficient lifestyle? Design a more in-depth study to find out why and how.
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