Watts Up?
Lighting accounts for approximately 20-25% of all electricity used in the U.S. On average, each
household uses about 5-10% of its energy for lighting. A commercial industry on the other hand uses
20-30% of their energy in lighting alone. 50% or more of the energy used is wasted by equipment,
inadequate maintenance, or inefficient use. Energy savings for lighting will require either a reduction in
use or more efficient use. The purpose of this activity is:
1. Compare the two types of lighting – incandescent and CFL bulbs.
2. Determine which one is more energy efficient and cost effective.
Equipment:
1. Watts Up meter
2. Incandescent night light
3. LED night light
Part 1 Procedure:
Note – the instructor may want to provide more kinds of light bulbs to test such as LED.
1.
2.
3.
4.
5.
6.
7.
Break up into groups of 4.
Examine the difference in light bulbs.
Plug in the Watts Up meter.
Plug in the lamp base into the Watts Up meter.
Screw in the incandescent light bulb.
Feel the light bulb and record any changes under observations in the table below.
Record the Wattage in the table below.
**Note – the incandescent light bulb will need to be cooled before unscrewing it.
8. Screw in the CFL bulb.
9. Feel the light bulb and record any changes under the observations in the table below.
10. Record the wattage in the table below.
Wattage
Incandescent light bulb
CFL
40
10
Conclusions:
1. How do your observations compare?
The incandescent light bulb is hotter than the CFL.
2. Which produces more heat?
Adapted by NDSCS from Clarkson University
Observations
hot
warm
Incandescent light bulb
3.
Which light bulb consumes more power (watts)?
Incandescent light bulb
4.
What is the energy loss from?
Excess heat
5.
The purpose of a light bulb is to provide light, not heat. Knowing this, explain the benefits of a
CFL bulb verses an incandescent light bulb.
Part 2:
We use electricity in our lives daily. Electrical appliances require varying amounts of power to operate.
Power (watts) is a measure of the instantaneous energy usage. Measuring the power use of an
appliance and the time it is used can be used to calculate the total electrical energy consumed.
Energy = power x time
(kWh = watts/1000 x hours)
Watt meters provide a convenient way to measure power consumption. Power consumption can also
be determined through the appliance rating stamped on the appliance. For example, light bulbs are
rated as “75 W” or “100 W” to indicate how much power they use and how much light is produced.
The purpose of this activity is to test the power consumed and estimate the energy consumed by several
appliances or other things plugged in around the classroom.
Procedure:
1.
2.
3.
4.
5.
Break into groups of four.
Decide on 6 – 8 appliances that are plugged in around your classroom to test.
Plug the watt meter into the wall and the appliance into the watt meter.
Record the watt reading and name of appliance in the table below.
Explore the various impact of various settings (for example, low versus a high setting on a hair
dryer). Record the power (wattage) consumed.
6. Estimate the time you use this appliance in your classroom. Record that time in the table below.
7. Continue on recording the wattages and time for all chosen appliances.
8. Calculate the energy consumed for each appliance in the table.
Answers will vary.
Adapted by NDSCS from Clarkson University
Appliance
Wattage
Estimated time
Energy (watts x time)
Conclusions:
Answers will vary.
1. Which of the appliances had a known power rating or current (amps)? How did your
measured power compare with the power specified on the appliance? Discuss any
differences. (Note – if current (amps) was specified, power can be calculated as Power =
volts x amps; the voltage of a standard power outlet is 120V).
2.
Which appliance did you expect to use the most power? Why? Did you find this to be true?
3.
Of the appliances tested, which one did you calculate to use the most energy? Is this what
you expected? Why?
4.
Based on your findings in this activity, can you suggest ways to conserve energy in your
class or home?
Part 3: Leaky electricity
Are your appliances ‘leaking’ electricity? Not only do we have more small and medium sized appliances
than ever before, but many of these never really stop using electricity even when they are turned off.
For example, if the TV has a remote, then part of the TV is always on, waiting for a signal from the
remote. People are usually not aware of this “standby consumption”.
A single appliance usually only leaks a small amount of electricity each hour, but since these appliances
leak electricity whenever they are not turned on, and since people have a lot of these appliances, the
amount of leaking electricity is significant. The average household spends about $40/year on leaking
Adapted by NDSCS from Clarkson University
electricity. The federal government is working with appliance companies and manufacturers to reduce
the amount of electricity that leaks out of new appliances.
Procedure:
1.
2.
3.
4.
5.
Break into groups of four.
Decide on 4 appliances that are plugged in around your classroom to test.
Plug the watt meter into the wall and the appliance into the watt meter.
Record the wattage in the table below.
Turn off the appliance and record the watt reading in the table below.
Answers will vary.
Appliance
Wattage (turned on )
Wattage (turned off)
Con
clusi
ons:
1.
Where there any appliances that did NOT read zero when turned off?
There may be some that do read zero and some that do not such as a computer.
2.
Was there an appliance that you expected to use electricity when turned off? Why?
3.
What can you do to ensure that there is no electricity being used when the power is shut off?
Unplug the appliance.
Part 4: Life cycle cost analysis
To answer the following questions please refer to the information provided below about 60-Watt
incandescent bulbs and 13-Watt CFL (Compact Fluorescent Lights). These two bulbs produce the same
amount of light.
Adapted by NDSCS from Clarkson University
Categories (units)
Watts consumed (W)
Rated Lamp Life (hours)
Electricity cost per kWh ($/kWh)
Cost per bulb ($)
1.
Incandescent
60
1000
0.10
0.25
CFL
13
8000
0.10
3.00 (average)
Calculate the amount of electrical energy consumed by each bulb type over a 8,000 hour period
in kilowatt-hours (kWh): kW = W x kW/1000W
a.
Incandescent bulb:
____60__________W = ___0.06________kW
____0.06_______kW X __8000_________hours = ___480________kWh
b. CFL:
____13__________W = ____0.013_______kW
____0.013_______kW X ___8000________hours = ___104________kWh
2.
Calculate the electricity cost per 8,000 hours for each bulb type.
a. Incandescent bulb:
___480__________kWh X __0.10______ $/kWh = $ ___48.00_____
b. CFL:
___104__________kWh X __0.10______ $/kWh = $ ___10.40_____
3. Calculate the number of bulbs used in the 8000 hour period.
a. Incandescent bulb:
__8000__________hours / ___1000_____ Rated lamp life (hours per bulb)
= ____8_________ bulbs
b. CFL:
___8000_________hours / ___8000_____ Rated lamp life (hours per bulb)
= ____1_________ bulbs
4. Calculate the total purchase cost of the bulb (or bulbs) used during the 8,000 hours.
a. Incandescent bulb:
___8____ # of bulbs used over 8,000 hours X $ __0.25___ per bulb
= $ ___2.00_______
b. CFL:
___1____ # of bulbs used over 8,000 hours X $ _3.00____ per bulb
= $ __3.00________
Adapted by NDSCS from Clarkson University
5.
Now calculate the total life cycle cost for each bulb type over 8,000 hour usage period. This is
calculated by adding the answer from question 2, the electricity cost, to the answer from
question 4, the bulb cost, for each bulb.
a. Incandescent bulb:
$ __48____ + $ __2.00____ = $_96.00______
b. CFL:
$ __10.40_ + $ __3.00____ = $__31.21_____
6. Based on your calculations of the total life cycle cost for each bulb, over a 8,000 hour usage
period, which bulb would save you money?
CFL
7. How much money would you save by your choice for each light bulb?
$64.80
8. How many light bulbs in your house do you think you can change to CFL’s? How much money
could your family save over 8,000 hours of light bulb use?
Answers will vary
Adapted by NDSCS from Clarkson University