Section I- Energy Usage in the United States

The U.S. is one of the world leaders in energy use and consumption. We will first look at some general trends in energy use vs. population growth.

The table below provides values for population and electrical energy consumption:

Year US Pop (Millions) Electrical Energy Use (Gwh) Gwh/ Mill Persons

1900 76 4

1910 92 20

1920 106 57

1930 123 114

1940 132 180

1950 151 389

1960 179 844

1970 203 1639

1980 227 2286

1990 249 2808

Directions:

1. Make plots of population vs. year and electrical energy vs. year using linear scales for both vertical and horizontal axes. Year is on the X-axis. Clearly label these lines on your graph.

2. Determine the log10 values for the population and energy values. Make additional plots of population(log10) vs year and electrical energy (log10) vs year. Year is on the X-axis. Clearly label these lines on your graph.

3. Estimate the doubling time for both the population and electrical energy growth by selecting appropriate points on your graphs. Indicate the selected points clearly.

4. Use the DT formula DT = 70/r to estimate the annual growth rate for both population and electrical energy.

5. From your graphs determine which is growing faster; population or energy use? Determine the energy use per million population and record the values

In the table above. Plot this column vs year and determine both the doubling times and annual growth rate for this per capita consumption.

6. Extrapolate the energy usage that will be required in the year 2030. How reliable will the estimate be? Hint: Consider our previous discussions on demographics.

Section II- Energy Usage at Home-

Energy Use of Some Typical Home Appliances

If you want a general estimate of how much electricity your home appliances consume, you can refer to the list below, which provides the energy consumption (Wattage) of some typical home appliances. If you have appliances that are not listed in the table, or desire a more exact figure based on a specific appliance in your home, use the following formula to estimate the amount of energy a specific appliance consumes:

Wattage ´ Hours Used Per Day
1000
= Daily Kilowatt-hour (kWh) consumption
(1 kilowatt (kW) = 1,000 Watts)

Multiply this by the number of days you use the appliance during the year for the annual consumption. You can then calculate the annual cost to run an appliance by multiplying the kWh per year by your local utility’s rate per kWh consumed.

For examples:

Window fan:

200 Watts ´ 4 hours/day ´ 120 days/year
1000
= 96 kWh ´ 8.5 Cents/kWh
= $8.16 /year

Personal Computer and Monitor:

(120+150) Watts ´ 4 hours/day ´ 365 days/year
1000
= 394 kWh ´ 8.5 Cents/kWh
= $33.51/year

Here are some examples of the range of nameplate wattages for various household appliances:

Aquarium = 50-1210 Watts
Clock radio = 10
Coffee maker = 900-1200
Clothes washer = 350-500
Clothes dryer = 1800-5000
Dishwasher = 1200-2400 (using the drying feature greatly increases energy consumption)
Dehumidifier = 785
Electric blanket- Single/Double = 60 / 100

Fans-

Ceiling = 65-175
   Window = 55-250
   Furnace = 750
   Whole house = 240-750
Hair dryer = 1200-1875
Heater (portable) = 750-1500
Clothes Iron = 1000-1800
Microwave oven = 750-1100
Personal Computer
   CPU - awake / asleep = 120 / 30 or less
   Monitor - awake / asleep = 150 / 30 or less
   Laptop = 50
Radio (stereo) = 400
Refrigerator (frostfree, 16 cubic feet) = 725
Televisions (color)
   19" = 110
   27" = 113
   36" = 133
   53"-61" Projection = 170
   Flat Screen = 120
Toaster = 800-1400
Toaster Oven = 1225
VCR/DVD = 17-21 /20-25
Vacuum cleaner = 1000-1440
Water heater (40 gallon) = 4500-5500
Water pump (deep well) = 250-1100
Water bed (w/ heater, no cover) = 120-380

Refrigerators, although turned "on" all the time, actually cycle on and off at a rate that depends on a number of factors. These factors include how well it is insulated, room temperature, freezer temperature, how often the door is opened, if the coils are clean, if it is defrosted regularly, and the condition of the door seals. To get an approximate figure for the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three.

Using the sources listed determine your:

1. kWh of energy consumed at your home for a 30 day period.

2. The estimated cost of the energy used by your electrical appliances (assume an average cost of 10 cents/kWh).

3. The United States EPA estimates that the following air pollutants are produced for each kWh of electricity that is produced:

900 g carbon dioxide ( a green house implicated in global warming) How much does your contribute for these pollutants?

1.9 g of nitrogen oxides (acid rain)

5.4 g of sulfur oxides (acid rain)

1. VCR’s use approximately 4 watts per hour to run the blinking clocks (which usually indicate 12:00). Assume they are running around the clock 24/7 how

Energy is required to run your household’s VCR’s?

Reference:Energy Efficiency and Renewable Energy Clearinghouse (EREC)
P.O. Box 3048 Merrifield, VA 22116
Voice (USA only): 800-DOE-EREC (363-3732)
Email: doe.erec@nciinc.com