Introduction

The Energy Story

  Energy Is Born
  Energy Types
  Energy Changes
  Energy Generation

The Energy Problem

  Conservation of Energy
  Aging of Energy
  Finite Resources
  The Oil "Crisis"
  Energy Pollution
  Discussion Topics

The Energy Solution

  Conserving Electricity
  Appliance Efficiency
  Heating Conservation
  Renewable Energy

Web Links

Teacher Guide

About the Author


Secret Lives Title - The Energy Solution


Conserving Electricity

Print out the table below and fill in the numbers and calculations that follow. For each of the appliances listed below you will need to look on that appliance and find its power rating in watts. You will also need to find out how much your energy utility or company charges you for your electricity. Then estimate how many hours that you use each appliance in a year. Finally, from this information, you can calculate for each appliance the energy use in kwatt hr/year and cost in $/yr. A set of sample calculations and some websites to help you out are given below the table.



Energy Inventory
Cost of Electricity: $ / kwatt hr = ___________
# Item Power
(kwatts)
Estimated
Time
(hr/yr)
Energy
Use

(kwatt hr/yr)
Cost

($/yr)
1 Toaster . . . .
2 Oven . . . .
3 Incandescent Lamp . . . .
4 Fluorescent Lamp . . . .
5 Television . . . .
6 Computer . . . .
7 Video Games (no TV) . . . .
8 Hair Dryer . . . .
9 Clothes Washer . . . .
10 Clothes Dryer . . . .
11 Table Fan . . . .
12 Hot Water Heater . . . .
13 Food Blender . . . .
14 Clock . . . .
15 Vacuum Cleaner . . . .
16 Space Heater . . . .
17 Clock Radio . . . .
18 Stereo (Amplifier) . . . .
19 CD Player . . . .
20 Power Drill . . . .
21 Torchiere Lamp . . . .
22 Coffee Pot . . . .
23 Refrigerator . . . .
24 Cordless Phone . . . .
25 Electric Blanket . . . .
26 Air Conditioner . . . .
27 Dishwasher . . . .
28 Microwave Oven . . . .
29 Small Freezer . . . .
30 . . . . .

Sample Calculations

Let's say that you found that your microwave oven has a power rating of 120 watts. To convert that into kilowatts you must divide by 1000 as follows. Place this number in the table.

120 w / 1000w = 0.12 kw

You estimate that your microwave oven is used 3 hours per day. Multiply by 365 days per year to get the hours used per year as follows:

3 hr/day x 365 hr/yr = 1095 hr/year

Now you can calculate your energy consumption by multiplying the power in kw times the time used in hr/yr as follows:

Energy = P t\E=(0.12 kw)(1095 hr/yr)=131.4 kw hr/yr

Finally, we can multiply the energy used in kw hr / yr by the cost in $ / kw hr to get the actual cost in $ / yr as follows:

Cost=(131.4 kw hr/yr)(0.077 $/kw hr)=$10.12 / yr

You may need to do a search on the internet or look at your electricity bill to find the cost per kw hr. The calculated numbers are shown in the sample table below.

Cost of Electricity: $ / kwatt hr = ___0.077__
# Item Power
(kwatts)
Estimated
Time
(hr/yr)
Energy
Use

(kwatt hr/yr)

Cost

($/yr)

28 Microwave Oven
0.120
1095
131.4.
10.12.

For more information on calculating your energy costs, check out the websites below.

Estimated US Electricity Costs Electricity costs in cents per kw hr for various areas and states in the United States.
Consumer Energy Information Sample calculations for calculating yearly energy use for appliances and power requirements.
Calculate Your Power Needs Includes a list of power requirements for a number of appliances.
Energy Units and Conversions Lists other popular energy units and the energy content of various fuels.