MEASURING ENERGY USAGE (2022)

National Teacher Enhancement Project
MEASURING ENERGY USAGE (1)

Middle School Home Energy Audit

MEASURING ENERGY USAGE

MEASURING ENERGY USAGE (2)
NTEP Home - Project Homepage - TeacherHomepage - Student Pages

Energy Use of Home Appliances

How much electricitydo our appliances use? You can usually find the wattage of mostappliances on the nameplate on the back or bottom of the appliance.The wattage listed isthe maximum power drawn by the appliance. Wattage = current Xvoltage. Often you will see the letters ULon the nameplate, which means the product has been tested to safetystandards. Adjusting volume or changing settings can affect theactual amount of power consumed. Many appliances draw small amountsof power even when they are turned off. These "phantomloads" occur inVCR's, televisions, stereos, computers and increase the appliance'senergy consumption a few watts per hour. Below is a list of somecommon household items and the wattage used for each.

APPLIANCE
WATTAGE
APPLIANCE
WATTAGE
clock radio
10
coffee maker
900-1200
clothes washer
350-500
clothes dryer
1800-5000
dishwasher
1200-2400
ceiling fan
65-175
hair dryer
1200-1875
clothes iron
1000-1800
microwave 750-1100 refrigerator 1725
computer: CPU
120
VCR/DVD
17-21/20-25
Computer: Monitor
150
19" color television
110
stereo
400
water bed
120-380
Now let's calculate the annual cost to run an appliance for a year.
MEASURING ENERGY USAGE (3)
Multiply this number by your local utility's rate per kWh consumed (In Denver the cost is 8.9 cents/kWh) to calculate annual cost.
EXAMPLE
If John uses a window fan (200 watts) 4 hours a day for 120 days per year, how much does it cost him to run his fan per year?
200 X 4 X 120 = 96 kWh
1000
96 kWh X 8.9 Cents/kWh = $8.16 per year
PROBLEMS TO SOLVE
After school each day, Sally uses her computer to do her homework. If she has an average of two hours of homework per night for 180 days of school per year, how many Kilowatt-hours are consumed and what is the annual cost of using her computer? A CPU and monitor use 270 Watts.
Choose a home appliance that you use and calculate your own energy consumption.
Appliance: _________________
Wattage: __________________
Hours used Per Day: ________
You can determine wattage, voltage and current using the following formulas:
wattage = current X voltage
current = wattage/ voltage
voltage = wattage/current
Fill in the chart below. The copier has been completed as an example.
APPLIANCE VOLTAGE CURRENT WATTAGE COST HOURS/YEAR ANNUAL COST
copier 115V 11A 1265W $0.08kWh 120 $12.00
printer 120V 5.5A
monitor 120V 2.0A
computer 200-240V 3.0A
fax machine 1.0A 45W
TV 120V 75W
microwave 120V 1500W
scanner 100-240V 2.0A
Lighting Dilemma

American homes contain over 3 billion lightfixtures. It takes about 138 billion kilowatt-hours of energyper year to operate these lights. 6-10% of our electricity billsare spent on lighting costs. The most common light bulbs in ourhomes today are incandescentor halogen bulbs. Thereare also Compact FluorescentLights (CFLs). Compact Fluorescent lights contain gas insteadof a wire filament. The electric current makes the gas glow, whichproduces very little heat. CFLs last up to 10 times longer anduse 70% less energy. Using energy efficient bulbs can both savemoney and natural resources.

How much energy/money can be saved by replacingour light bulbs with Compact Fluorescent Lights?

1. Search your home and count the number of lights in each room. Each halogen light uses three times the energy and must be counted three times.
2. Calculate the number of hours the lights are used in each room each day.
3. Enter the data below.
Number of lights Number of hours Lights X hours = TOTAL
Living Room
______________
______________
_____________
Dining Room
______________
_____________
______________
Kitchen
______________
______________
______________
Bedrooms
______________
______________
______________
Bathrooms
______________
______________
______________
Hallways
______________
______________
______________
Family Room
______________
______________
______________
Outside Lights
______________
______________
______________
TOTAL
______________

Each energy efficient CFL bulb saves 50 watts,how many watt-hours could you save if you replaced all bulbs withCFLs?

Total hours of operation X 50 watts = _________Watt hours you would save each day

Divide your answer by 1,000 since there are1,000 watt-hours in a Kilowatt-hour (which is how your utilitybills you)

Watt hours / 1,000 = _______________ kilowatt-hours you would save

Take this answer and multiply it by 365 (thedays in a year) to calculate the Kilowatt-hours saved in a year.

Kilowatt hours X 365 = __________Kilowatt-hours saved in a year

To calculate the amount of money your familycould save in a year, take the Kilowatt-hours saved in a yeartimes the cost per Kilowatt-hour ( in Denver it is $.089).

Kilowatt-hours saved X $.089 = ______________Amount saved per year!

In addition to saving money, we use less electricity!Using less electricity means producing lessgreenhouse gases. If we assume that every kilowatt-hour savedremoves 2 pounds of carbondioxide from the air, how much greenhouse gases could be prevented?

Kilowatt-hours saved in a year X 2 pounds = _______________pounds of greenhouse gas prevented

Reading Electric Meters

Understanding how we use energy can help usbetter conserve energy. Many different energy sources are usedto generate electricity-but more than half of the electricityin the United States is generated by coal-fired power plants.Electricity enters a home through a distribution line that passesthrough a meter that measures the amount of electricity consumedin kilowatt-hours.

Reading an electric meter is easy. The faceof the meter has five dials with the numbers 0-9 on each dial.The dials are not identical though. On the first dial, the numbersincrease in a clockwise direction. On the next meter, the numbersincrease in the opposite direction, in a counter-clockwise direction.Each dial alternates from clockwsie to counter-clockwise as shown.To read a meter, you read the dials from right to left and recordthe numbers. If the pointer is between two numbers, you alwaysrecord the smaller number.

EXAMPLE

Monday morning the meter looked like this:

MEASURING ENERGY USAGE (4)
MEASURING ENERGY USAGE (5)

Friday morning the meter looked like this:

MEASURING ENERGY USAGE (6)
MEASURING ENERGY USAGE (7)

The meter reading Monday would be 40565 and on Friday it would be 41615

To figure out how much electricity was used, subtract Monday's reading from Friday's reading like this:

41,615 - 40,565 = 1,050 kilowatt-hours

Based on electricity costs in Denver of $.089 per kilowatt-hour, the total cost would be: 1,050 X $.089 = $93.45

PROBLEM TO SOLVE

On January 1, the meter looked like this:

MEASURING ENERGY USAGE (8)

On January 31, the meter looked like this:

MEASURING ENERGY USAGE (9)

How many kilowatt-hours of electricity were used during January?

If the cost of electricity in Denver is $.089 per kWh, how much did electricity cost for January?

What is the average cost of electricity per day during January?

Monitor home energy use by reading the electricmeter each morning for a week and determine the cost per weekof electricity in your own home.

Turn off the power for just one hour. Monitorelectricity during a normal hour at home and then turn off asmany electrical devices as possible for an hour and record thedifference in electrical use.

How To Read Utility Bills

Electric companies monitor electric consumptionwith meters that measure the amount of electricity consumed inbuildings. Electricity is measured in kilowatt-hours-kWh. Theaverage cost of electricity in the US is approximately eight cents.

Utilities usually read meters once a month,although some utilities read meters every other month and estimatereadings for teh months inbetween. Bills are sent to customersmonthly, providing detailed information on the amount of energyconsumed and the rate structure for billing.

Many customers can opt for a budget plan, inwhich they pay the same amount to the utilities each month, regardlessof the actual amount of energy they use. This spreads out theseasonal fluctuations in energy use-high heating costs in winterand high cooling costs in summer.

Look at the sample electric bill below. Usethe information provided to answer the questions that follow.

BUZZ LITE ENERGY COMPANY

DATE
METER READING
DECEMBER 1
970
DECEMBER 8
1040
DECEMBER 15
1230
DECEMBER 22
1410
DECEMBER 29
1640
JANUARY 2
2260
JANUARY 9
2370
JANUARY 16
2680
JANUARY 22
2920

1. Using the meter readings from January 9thand December 8th, what was the total kilowatt hour usage?

2. Calculate the actual cost by using the rateschedule. Show your work for each step:

UTILITY RATES:

basic charge(your cost to be connected to the Utility company) ($7.00) +

kWh first 800 ($.06) +

kWh over 800 ($.08) = (your cost) =$ ___________

Students: Click on the button at the left to connectto the Measurement Worksheet

Created for the NTEP II FermilabLInC program sponsored by FermiNational Accelerator Laboratory EducationOffice and Friendsof Fermilab, and funded by UnitedStates Department of Energy, IllinoisState Board of Education, NorthCentral Regional Technology in Education Consortium whichis operated by North Central RegionalEducational Laboratory (NCREL), and the NationalScience Foundation.
Authors: Sue Emmons,Powell Middle School, Littleton, CO; KevinLindauer, John F. Kennedy High School, Denver, CO; LindaLung, National Renewable Energy Laboratory, Golden, CO; John Sepich, Scott CarpenterMiddle School, Westminster, CO; ; JanetStellema, Monarch K-8, Louisville, CO.
Created: September 9, 1998 - Updated: October 3, 2001.
URL: /ntep/f98/projects/nrel_energy_2/measurement.html

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