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Efficiency is a ratio — a rate of comparing how much energy is put into something compared to how much energy is used to create the desired process. Look at the example of making a pie. To make a pie, you have to prepare the filling of apples. You need to peel the apples, remove the seeds, and make apple slices. Maybe it takes you 10 pounds of apples to make one pie. Your mother can make two pies with that same 10 pounds. She has just as much filling in each of her pies as you do. Mom is just better at peeling so she wastes less apple. She is more efficient with the apples by a ratio of 2:1. She makes two pies for every one pie you make.

Efficient Appliances and Processes
Efficiency is used to talk about refrigerators, air conditioners, furnaces, freezers, cars, windows, and practically every appliance that requires energy to run. All major appliances (washing machines, ovens, refrigerators, air conditioners) have energy guides. These guides tell you how much it costs to run the appliances for a year. Appliances that are more efficient than their counterparts often have an Energy Star Label.

The Energy Star label tells the buyer that this appliance is more efficient that similar models of the same appliance. This is a voluntary program for manufacturers.

Appliances aren't the only items that we can use when we talk about efficiency. Processes can also be rated. An older energy plant that uses coal to generate electricity is not as efficient as a brand new plant that generates electricity from the same coal. Coal may not be burned completely in the older plant. Or there may be a lot of wasted heat that escapes through the process. Newer systems and equipment are usually much more efficient at using energy to create a product than models that are even just ten years old. Technology improves efficiency.

Energy efficiency in a typical thermal electric power plant

Start with chemical energy in coal
100 units
Heat loss in stack gases
-10 units
Heat loss in cooling water
-50 units
Electrical transmission losses
-3 units
Total losses
= 63 units
Electrical energy delivered
37 units
Energy efficiency of the plant


Cars and Efficiency
Cars are a huge part of the efficiency issue. According the 2001 Urban Mobility Report, 6.8 gallons of excess fuel are consumed during rush hour traffic delays in a year. That means when your car is stuck in traffic, it keeps using energy (in the form of gasoline) that is wasted. And that isn't the only bad news for cars. Fuel economy for cars is actually decreasing to its lowest levels since 1980. Cars built in 2001 average 24.5 miles per gallon. Compare this to 24.7 miles per gallon for cars built in 2000. Would you believe cars in 1987 got 26.2 miles per gallon. Why the decline? Larger vehicles, like trucks and SUVs, are more popular than ever, and use more gasoline than smaller cars.

Doing More With Less
Energy efficiency doesn't mean doing without. No one wants to go back to life before microwave ovens and air conditioning. What efficiency means is that we do more with less. We create products that do the most possible work with the least amount of energy. We make tools more efficient. What possibilities do you see for efficiency in your future?

Check it Out!
A vampire appliance is an appliance that uses energy even when it is turned off. Any appliance that uses a remote control is a vampire appliance because it uses a little bit of electricity to stay in a stand-by mode, so when you push the ON button, the machine goes on right away. Computer monitors are another vampire appliance. Many people do not shut off their monitors when they shut down their computers. Turning off the monitor over night can save you as much as $50 per year in electricity!




PBS NewsHour Online Links

Experts debate more efficient AC.

Greener Cars! Research is looking at how to improve the efficiency of Sport Utility Vehicles (SUVs). This PBS NewsHour site examines SUVs and what is being done to increase their gas mileage. Or check out how to create greener cars.

Web Links
This Home Energy Audit Worksheet was developed by Economic Research Associates (Eugene, Oregon)for use by the Iowa Association of Municipal Utilities, its members utilities and their customers.

This Home Heat Loss Quiz was adapted for use by the Iowa Association of Municipal Utilities, its member utilities and their customers. It is intended to give you and idea of how well your home is weatherized and insulated. You simply answer a series of questions, and then assign points for each answer.

Stopping Air Leaks
Many older homes waste a lot of energy because of air leaks. If you can find and seal those leaks, you can save energy and money – up to $150 a year for an average household.

Home Insulation
Adding insulation to your attic, walls, basement, and sill boxes is like wrapping your home in a warm blanket during the winter. To maintain comfort in the winter, the heat lost through uninsulated walls, floors, and ceilings must be replaced by your heating system. In the summer, your home gains heat through uninsulated surfaces.

Appliance Efficiency
Today's refrigerators and freezers use a third of the energy used by a model manufactured in 1973.

Energy Guide Label Explained
The EnergyGuide information is designed to help you compare the annual energy use or efficiency of competing brands and similar models. Look for the distinctive yellow-and-black label on clothes washers, dishwashers, refrigerator/freezers and water heaters, as well as on home heating and cooling equipment.

Energy Star
ENERGY STAR is a government-backed program helping businesses and individuals protect the environment through superior energy efficiency.

2010 Motor Challenge
This new program, a joint effort by the U.S. Department of Energy (DOE), industry, motor/drive manufacturers and distributors, and other key participants, is putting information about energy-efficient electric motor system technology into the hands of people who can use it.

How Much Energy do your Light Bulbs require?
The typical incandescent light bulb wastes 90 percent of the energy it uses, producing heat rather than light. A breakthrough in lighting technology called the compact fluorescent is a more efficient alternative to the incandescent bulb.