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Middle School Home Energy AuditENERGY EFFICIENCY |
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Middle School Home Energy AuditENERGY EFFICIENCY |
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Imagine being able to complete your homework in a half an hour each night versus the usual two hours of homework! Which would you choose? When are you being most efficient?
What is energy? It fuels our cars, plays our radios, heats our water and lights our homes. Energy is the ability to do work. We can use energy to put something in motion or produce light and heat. Think about how much energy you use each day. You wake up using an alarm clock, take a shower using hot water, use appliances in the kitchen to prepare your breakfast and use a school bus as transportation to get to school. But how much energy do each of those use? How efficient are they?
Energy efficiency is the amount of useful energy you get from a system. Converting energy from one form to another always involves a loss of usable energy, usually in the form of heat. While it would be great to have a perfect energy efficient machine, it simply isn't possible. However, today we are making appliances that use less energy than they did many years ago. The National Appliance Energy Conservation Act was passed in 1990 and now requires appliances to meet energy efficiency standards.
When you buy appliances, they are labeled with a yellow EnergyGuide Label which gives you the Energy Use and Energy Efficiency Rating (EER). The EnergyGuide labels list the manufacturer, the model, the capacity, the features, the amount of energy the appliance will use a year on average, it's comparison with similar models, and the estimated yearly energy cost. Since many high-efficiency appliances cost more to buy, is buying the less energy efficient appliance the bargain? What you need to factor in is how much it costs each year to operate and how many years you will use it. The payback period is the amount of time you must use an appliance before you benefit from energy savings. The life cycle cost of an appliance is the purchase price plus the operating cost over the projected life of the appliance. Life cycle costs of efficient appliances is usually much less than cheaper appliances.
Calculating Lifecycle Costs—How much will an appliance cost to buy and use over a lifetime?
purchase price + (annual energy cost x estimated lifetime x discount factor) = lifecycle cost add appliance characteristics table from nimo.com
Calculating Payback Period—How long will it take to recover the extra money you spend for a more efficient appliance?
purchase price of more expensive model - purchase price of less expensive model = payback period
purchase price of more expensive model - lower annual operating cost = ???? Example: You are shopping for a refrigerator. There are two models. One casts $100 more than the other but uses $25 less electricity per year. Which refigerator should you buy?
It would take 4 years to realize the savings. However, since the payback period is only 4 years and your refrigerator will last much longer than that, you will save money over the life of the rerigerator and conserve natural resources.
$1000 purchase price of more expensive model - $900 purchase price of less expensive model = $100 $100/$25 less electricity/yr = 4 yrs
Use these links to learn more:
Did you see a word or two that you did not recognize? You might find it in the glossary below.
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Authors: Sue Emmons, Powell Midddle School, Littleton, CO; Kevin Lindauer, Baker Middle School, Denver, CO; Janet Stellema, Monarch K-8, Louisville, CO; John Sepich, Scott Carpenter Middle School, Westminster, CO; Edited by Marge Bardeen NTEP II Project PI.
Webmaster: ed-webmaster@fnal.gov
Created: September 9, 1998 revised July 30, 2001
URL: /ntep/f8/projects/nrel/student/energyefficiency.html
