Household Electricity Use Worksheet
Evaluation of Household Appliance Electricity Use
Part 1: Calculating operating cost for an appliance
In order to calculate the average operating cost for any electrical appliance you can
use the following formula:
kWh = (watts/1,000) x hours of operation
Cost = rate (cost/kWh) x kWh
Watts can usually be found on the appliance name plate. If the name plate lists
amps: volts x amps = watts
Example: How much does it cost to operate a portable electric heater? An electric
heater wattage is usually given on the unit itself, or with the literature that comes
with it. An example is 1000 watts. If you use the heater an average of 45 hours
during winter months (1 /2 hour per day for the three winter months). If the electric
rate during the winter is $0.068 per kWh. So
kWh = 1,000 watts/ 1,000 x 45 hours = 45 kwh
cost = 45 kWh x .068/hour = $3.06
Now, if you have an 8 amp heater, the calculation changes just a bit:
8 amps x 120 volts household current = 960 watts price = .96 kW x 45 hours x
S.068/kWh = $2.94
1. Chose an electrical appliance in your house, either a computer or a television set.
Look at the back of the appliance. You will either find the power in Watts, or the
current in amps.
Appliance: ______________
=______ amps
power =________watts or current
2. Unless you know otherwise, assume that the appliance is receiving 120 volts of
household current. In Los Angeles at this time the electric rate is $0.10 per kWh
3. Estimate the number of hours that the appliance is used in one month: ____
hours
4. Calculate the energy in kWh that is used to run your appliance for one month.
Show your calculations below
5. Calculate the cost per month of using the appliance.
Part 2 -Calculating Household Appliance Energy Use
Listed below are some common appliances, their wattage, and average monthly use.
Determine your household energy use by estimating your average hourly use of each
appliance, and then the cost per month. Many of the appliances your family will not use,
while there will be other appliances, such as a computer, that your family may use which
you must list at the end. For some appliances, you ‘l1 also have to indicate the number of
each appliance used (light bulbs and clocks for example).
Appliance
Watts
U.S. average
hours/month
Air Conditioner
(Room) 6,000 BTU
Air Conditioner
(Room) 9,000
Air Conditioner
(Central) 2.5
Can Opener
Ceiling Fan
Clock
Clothes Dryer
(Elec)
Clothes Dryer (gas)
Clothes Washer
Coffee Maker
Computer (printer
and monitor)
Dehumidifier
Dishwasher
Electric Blanket
Portable electric
heater
Portable fan
Food blender
Food freezer
(1.5ft3)
Frying pan/waffle
maker
Furnace fan motor
750
120-720
1050
120-720
3500
240-860
175
60
5
5000
0-1
15-330
720
6-28
500
500
90
200
6-28
7-40
4-30
25-160
350
1300
180
1000
120-720
8-40
30-90
30-90
115
390
335
18-52
3-5
180-420
115
10-20
350
160-415
# in house
Your personal
ave.
hours/month
Your cost
($) per
month
Hairdryer
Single lamp
Compact
fluorescent
2 tubes fluorescent
Microwave oven
Electric stove
Refrigerator
Stereo receiver (on)
Setero receiver
(standby)
TV on
TV standby
Toaster
Electric toothbrush
Vacuum cleaner
VCR/DVD player
on
VCR/DVD player
standby
1200
60-150
18
1-10
17-200
17-200
100
1000
12500
500
235
2
10-200
5-30
10-50
150-300
1-170
500-720
80
5
1150
10
800
40
60-440
280-660
1-4
1-2
2-6
50-200
3
420-670
TOTALS--Æ
Part 2:
Your assignment is to decrease your electricity use by at least 7% for one week.
First determine what you would use in a normal week then conserve energy for
the second week. Describe in detail what changes you made and how you
obtained the data.
The Report:
It is important that you make some kind of measurement so that you can quantify
the savings. The most direct way to do this is to read your electricity meter. If this
is not possible, then you need to consult with your instructor about an alternative.
In addition to reading the meter, you are asked to calculate the savings in energy
expected from your conservation plan. This requires that you decide what
appliances you will replace or restrict, then find the power they use, and finally
estimate the number of hours of saving which you have accomplished. The report
comes in FOUR parts (A, B, C, D).
Your Electric Meter
Read the dials from left to right and write down, in the same order, the last
number that the pointer has passed. The result is your meter reading.
If the pointer is directly on a number, record
the next lower number unless the pointer on
the dial to the right has passed 0. The
reading at the right is 7025
A. READING YOUR METER - Due on
____________________
To be certain that you are reading the electrical meter correctly, you are to make a
first reading and report the result. You are to record here the appearance of the 4
or 5 dials on your meter. Then
1. WRITE in all of the numbers on the dials,
2. use arrows to show the direction each pointer moves,
3. and show the positions of the pointers as they appear.
4. Then write down the number of kilowatt hours that this reports, and finally
record the time and date upon which this reading was made.
DIALS:
1. Reading = _________________ kWh
________________
Time: ______________ ; Date:
B. NORMAL USAGE - Due on_______________
Record the second reading of your electrical meter
DIALS:
2. Reading = _________________ kWh
________________
Time: ______________ ; Date:
Report here the number of kilowatt-hours used during a week of normal
electrical usage. If the time between your meter readings was not one week (to
within about four hours) then you will need to calculate what would be used in a
day, and then change it to a week. Show your work
3. Amount of electricity used during the first week = _________________
C. PLANNED SAVINGS - Due on __________________________
Here you are to indicate how you expect to save electrical energy usage,
and the quantity that you expect to save. You may change more than one thing.
4. How you plan to change your use of electricity?:
How to Estimate your savings
For the appliances, light fixtures, or motors that are to be used for a reduced
amount of time during the test week, you need to find out (a) the power each
appliance uses and (b) an estimate of how many hours it is normally used in a
day or week, and how many hours this will be reduced in a day or week. You will
then calculate the saving expected in a week.
Examples:
•
•
•
•
•
•
For the electric motor on the washing machine the data might be 400 watts used 5
hours a week to be reduced (by using larger loads) to 3.5 hours. The savings
would be
Savings = (0.400 kW) x (1.5 hrs) = 0.600 kWh
For appliances that are replaced by others requiring lower electrical power you
need to find out (a) the power used by your appliance, (b) the savings in power
from the new appliance, and (c) an estimate of the number of hours this appliance
is used in a week. You then calculate the savings expected in a week.
For a light fixture with three 75 watt bulbs that that is replaced with three 20 watt
compact fluorescent bulbs which are used two hours a day, the savings would be
calculated as
Power difference = (75 - 20) x 3 = 165 watts =0.165 kW
Energy savings = (0.165 kW) x (2 hrs/day) x (7 days/wk) = 2.31 kWh
Estimate of Savings- (show work)
D. FINAL REPORT - Due on _________________
Record the third reading of your electrical meter
DIALS:
Reading = ___________________ kWh
________________
Time: ______________ ; Date:
Amount of energy used during the second week = ___________________
CALCULATIONS: Show all work
(There are 101 million households in the United States)
(The cost of 1 kWh is approximately $0.10, and one KWH produces 1.5 lbs of
CO2)
1. Energy savings from the first week to the second week (as determined by meter
readings)
2. % decrease in energy use
3. Energy savings in one year
4. Money savings in one week
5. Money savings in one year
6. Energy saved if 10% of the households in the United States did the same for
one year
7. A typical coal-burning power plant produces 3.5 billion kwh per year. How
many power plants could shut down if 10% of the U.S. households did the same
you did?
8. Lbs of CO2 saved if 10% of the households in the United States did the same
for one year.