What is Energy Efficiency?

Instructor: Josh Corbat

Josh has taught Earth Science and Physical Science at the High School level and holds a Master of Education degree from UNC-Chapel Hill.

With the threat of global warming growing greater each day, the topic of energy efficiency is on the minds of many people. In this lesson, find out what is meant by energy efficiency, and discover how you can increase yours on a daily basis.

Energy Efficiency

Think about all the things you have done recently to reduce your use of natural resources. Maybe you have taken shorter showers or turned off lights when you're not using them. Perhaps you have chosen to ride a bike to certain places instead of hopping in the car. These are all great examples of actions we can all take to increase our personal energy efficiency. With these actions in mind, it's easy to guess the definition of the phrase 'energy efficiency.' However, it is a bit more complicated when we look at this topic from a scientific point-of-view. There are actually two very important definitions for the phrase. Luckily, they are very closely related.

In science, energy efficiency has two definitions:

  1. The energy efficiency of an individual or group refers to their use of energy (electricity, fuel, etc.) and its impact on the planet.
  2. Energy efficiency can refer directly to machinery that uses an energy input (electricity, fuel, heat, etc.) and converts it to a usable output (electricity, heat, etc.). The percentage of energy efficiency can then be calculated using the formula: (output/input) x 100.

In the second definition, the efficiency of the machine depends on how much output is produced compared to the amount of the input. The greater the output when compared to the input, the higher the energy efficiency.

Energy Efficiency in Our Daily Lives

When discussing energy efficiency in our daily lives, we're really talking about the first definition given above. There is no denying that in order to reduce our energy use on a planetary level, individuals and groups must all play their part. In particular, you have probably noticed a lot of talk lately about reducing the energy use in our homes. There are many methods by which to do this, but I'm going to give one example that you've probably heard of: light bulbs.

The traditional style of light bulb that has been in use for many years is called the incandescent bulb. Incandescent bulbs are the typical shape of bulb that you would draw if you ever found yourself needing to draw a light bulb (perhaps you've created a comic strip in which someone suddenly has a great idea). These bulbs, although very easy to make cheaply, are incredibly inefficient. They produce a lot of heat when they are in use, which means that some of the electricity being used to light the room is being wasted. In electrical devices, heat means waste (unless, of course, we're talking about a toaster or hair dryer, in which case, heat is the main point).

New styles of light bulb that have come on the scene within the last ten years or so include compact fluorescent light bulbs (CFLs) and LEDs (which stands for light-emitting diodes). CFLs have become much cheaper in recent years, making them an obvious choice if many bulbs are being purchased. They do not produce nearly as much heat as incandescent bulbs and are, therefore, far more efficient. LED bulbs are even more energy-efficient yet, but are so new that they are still quite expensive (as of the writing of this lesson, that is).

A common compact fluorescent bulb. CFL bulbs are far more energy-efficient than traditional incandescent bulbs.
CFL bulb

Using new technologies, we can all play our part in reducing our use of energy in our daily lives, but what if that energy were more efficiently produced before it even came to us?

The Energy Efficiency of Machinery

One of the main goals of modern society is to reduce our use of energy on a greater scale than within individual homes, which is the focus of our second definition of energy efficiency. One way to do this is to produce usable energy (electricity and fuel, primarily) more efficiently. Many studies are currently underway to try to increase the efficiency of two types of machinery in particular: power plants and engines.

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