ENERGY STAR®, a U.S. Environmental Protection Agency
program, helps us all save money and protect our environment
through energy efficient products and practices. For more
information, visit www.energystar.gov.

Comparing Light Bulbs
This activity is based on the "Comparing Light Bulbs" activity produced by the National
Energy Education Development (NEED) Project. For information about NEED'S
materials and to access more energy efficiency activities, go to ¦www.NEED.org.	
Grade Levels: K-5
Brief Description:
Too many greenhouse gas emissions are collecting in our earth's
atmosphere and are causing our climate to change. People at any age
can help by using less energy. In this exercise, students will use a light to
demonstrate the difference between being energy-efficient and energy-
wasteful, and learn what energy efficiency means. After the lesson, they
should be able to discuss the following:
•	How does using less energy help our environment?
•	Do compact fluorescent light bulbs and standard light bulbs create
the same amount of light?
•	How do you know if one light bulb is more efficient than another
light bulb?
•	What is one way we can save energy at home?
•	Brainstorm: What are other ways we can save energy?
We have all heard about global climate change (also referred to as global
warming) and know that it is a challenge facing our world. Most people do
not know that the average home is responsible for twice as many
greenhouse gas emissions as the average car. Most of the electricity we
use at home comes from burning fossil fuels like coal and oil, which
releases greenhouse gas emissions into our earth's atmosphere. What
this means is that we can each play a role in reducing these emissions by
using energy more efficiently.
One of the easiest ways to learn about energy efficiency and put it into
practice at home is through the light bulb. The most common light bulb
today is the incandescent light bulb invented by Thomas Edison 125 years
ago. However, new compact fluorescent light bulbs (CFLs) use 75% less
energy and last up to 10 times longer. In fact, only 10% of the electricity
used by an incandescent bulb is used for light, and the other 90% escapes
as heat. CFLs create the same amount of light, but generate a lot less
heat - about 75 percent less. CFLs are more energy-efficient than
incandescent lights because fluorescent technology does not need to heat

a metal filament to create light, but instead use gases that require less
electricity to create the same amount of light. Every CFL can prevent
more than 400 pounds of greenhouse gas emissions over its lifetime. To
save the most energy and do the most good for the environment, it is best
to use CFLs in frequently used areas of the home.
Because CFLs contain a small amount of mercury, about 5 milligrams, they
should be disposed of responsibly, ideally recycled; and, if they should break,
cleaned up using EPA's guidelines. Learn more at
Possible Hypotheses:
•	Incandescent and CFL bulbs do/do not produce the same amount
of heat.
•	Incandescent and CFL bulbs do/do not produce the same amount
of light.
•	One bulb is/is not more energy efficient than the other.
•	One incandescent and one
CFL bulb that produce equivalent
lumens (light levels). For example,
a 60 watt incandescent bulb and a
13 watt CFL will generally produce
equivalent light levels. Choose an
•	Thermometer
•	Lamp, or watt meter
comparator (if available)
1.	Have an adult place the CFL bulb in the lamp and turn it on.
Observe the light that is produced. (Or, place the CFL bulb and
incandescent in a watt meter comparator, in order to switch back and forth
between the bulbs and show the meter speed up and slow down).
2.	Hold a thermometer six inches above the bulb for one minute and
record the temperature Turn off the lamp and let the bulb cool.
3.	Have an adult remove the CFL bulb, place the incandescent bulb in
the lamp and turn it on. Observe the light that is produced.
4.	Hold a thermometer six inches above the bulb for one minute and
record the temperature.

Analysis and Conclusion:
•	Could you tell any difference in how much light the two bulbs
•	Did one bulb produce more heat than the other?
•	Which bulb is more energy efficient?
•	Which bulb will prevent more greenhouse gas emissions in our air?
Extension Activities:
Using Math
Demonstrate to the class how to compute the actual electricity
consumption of the two bulbs for varying time periods of use; have the
students approximate how long they leave lights on (i.e. one hour of use,
how many times a week, how much over the year). Compare the amount
of electricity used for the two bulbs for similar amounts of time (have
students do this if this is appropriate). Compare the cost of the two bulbs
based on the electricity consumed. Compare the amount of greenhouse
gases produced based on the electricity consumed.
Electricity used (kWh) = hours of use x (wattage of bulb divided by
Cost = kWh x electric rate
Greenhouse Gas Emissions (pounds of pollution) = kWh x 1.58
Using Language Arts
Have the students discuss the benefits of using more energy efficient
bulbs (i.e. saves money, saves time replacing bulbs, helps protect the
environment by reducing fossil fuel emissions). Brainstorm about why it is
important for them to do their part in helping to improve the environment.
Talk about how energy is used in their homes and schools and help them
identify other ways that energy is being wasted. Have the students draw a
picture or write a short story about the importance of individuals in bringing
about larger social changes and illustrate the difference that something as
simple as changing a light can make when we all do our part.