A Tale of Three Light Bulbs
NAME: __________________________
DATE: __________________________
Purpose: Compare Compact Fluorescent (CFL) bulbs, Light Emitting Diode (LED)
bulbs and incandescent light bulbs
Research: Find three articles about the differences between the three types of bulbs.
Record at least four facts from the articles. What do the experts say about how the
bulbs compare in terms of cost, light output, temperature, energy use, and value? Cite
specific examples from the articles that support your facts.
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Form a hypothesis that you can test. Make a hypothesis about which one of the bulbs
would be a better choice for a particular reason after comparing the three types of
bulbs. Your hypothesis should be supported by your research.

Which light bulb will generate the most heat? The most light?

Which light bulb will use less energy? Last longer? Cost less to operate?
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1
Materials per group:
 1 Kill-a-Watt meter with light socket
converter
 1 CFL bulb
 1 incandescent bulb
 1 LED bulb
 1 extension cord
 Energy Conservation Wheels (one for
each student)
Procedure
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Plug the Kill-a-Watt meter into the extension cord. Be sure the socket is plugged into
the Kill-a-Watt meter.
Carefully remove the incandescent bulb (GE Soft White) from the box and twist the
bulb into the socket.
Then plug the extension cord into the power outlet in the wall.
Press the WATT Button on the Kill-a-Watt meter.
Record that number of watts in Column A of the “Watt’s Your Consumption?” table
(Table 1). You may need to wait a moment for the numbers to stabilize.
Without touching the bulb, hold your hand above the bulb to feel if heat is being
generated. Record your observations of the temperature of the air around the light
bulb in Table 2. Heat Generation (check: hot, warm, or cool).
Remove the bulb from the socket using the base only (bulb may be hot).
Return the bulb to its box and protective wrapping.
Repeat steps 1-8 for the compact fluorescent bulb (TCP Spring Light; spiral bulb)
and the LED bulb (Kobi Electric).
Fill in columns B-G of Table 1 by following the equations listed under each column.
Fill in columns J-L of Table 3 by following the equations listed under each column.
Compare your answers in each Table and then answer the questions in the
Conclusion section at the bottom.
2
Results
Table 1. Watt’s Your Consumption?
Light Bulb
A
B
C
Watts
Kilowatts
Hours
Hours
Kilowatt
Energy
Pounds
per
per
hours
Cost per
CO2/mo.
month
(kWh)
month
used
per month
Type
(A/1000)
day
used
D
(C x 30)
E
used
(B x D)
Incandescent
3
Compact
3
Fluorescent
Light
3
Emitting
Diode
Table 2. Heat Generation
Light Bulb Type
Hot
Warm
Cool
Incandescent
Compact Fluorescent
Light Emitting Diode
3
F
(E x
$0.10/kwh)
G
(E x .03)
Table 3. Life Cycle Cost
H
I
J
K
L
M
Light Bulb
Purchase
Estimated
Total KWh
Total Cost
Total Life
Total
Type
Price of
Life of
Used over
of
Cycle Cost
Cost of
Bulb
Bulb
Life of Bulb
Electricity
of Bulb
Bulb per
(months)
(Column E x
Column I)
over Life of
Bulb
(Column K +
Column H)
(Column J x
month
(Column L
Column I)
$0.10/kwh)
Incandescent
$0.85
12
Compact
$2.70
111
Fluorescent
Light
Emitting
$22.00 277
Diode
Conclusion
Questions:
1. Which bulb used the least amount of power? ___________________
2. How much more money per month does it cost to power an incandescent versus a
CFL? ___________________
3. How much more money per month does it cost to power an incandescent versus a
LED? ____________________
4. How many more pounds of CO2 does an incandescent give off per month versus a
CFL? _____________________
5. How many more pounds of CO2 does an incandescent give off per month versus a
LED? _____________________
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6. If you have 5 incandescent light bulbs at your house, burning 3 hours a day, how
much money would you save on energy per month if you replaced all 5 bulbs with
CFL’s? ___________________
7. How much money would you save on energy per month if you replaced all 5
incandescent bulbs with LED’s? ________________
8. Taking into account the purchase price of the bulb, how much more money per
month does it cost to use an incandescent versus a CFL? ______________
9. Taking into account the purchase price of the bulb, how much more money per
month does it cost to use an incandescent versus an LED? _____________
10. Fill in the Table below to calculate how many months it would take to pay for a
lighting retrofit as well as how much that retrofit would save over the life of each type
of bulb.
Light Bulb
N
O
Payback Period
Total Savings Over Life of
Bulb
Change
Replace
Incandescent
Purchase Price CFL
Answer Q.#2
(Life of CFL- Payback Period) x
Answer Q.#2
with CFL
Replace
Incandescent
Purchase Price LED
Answer Q.#3
(Life of LED- Payback Period) x
Answer Q.#3
with LED
5
11. After this lesson, explain which light bulb you would choose to have in your house
citing evidence from both your research and your experiment to support your choice.
12. Review the Energy Conservation Wheel. Identify three strategies that you could
implement to reduce your energy use at home.
13. Think about how energy is used at your school. Identify three ways that you may be
able to help reduce energy use in your school.
14. Review your research and your experiment and write a conclusion recommending
the best light bulb to use for both cost and energy savings. Be sure to support your
recommendation with specific evidence from your work. Explain how this supports
or disproves your hypothesis?
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