The Cost of Electricity
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Bakersfield College *
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Industrial Engineering
Date
Dec 6, 2023
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docx
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Uploaded by SuperHumanHeatLobster20
The Cost of Electricity
Watts and kilowatts are measurements of the work being done as electric current passes through a
circuit.
The higher the wattage of an appliance or device, the more work is being done and the more
electricity is consumed.
One kilowatt is equal to one-thousand watts. You can convert using this formula:
Watts / 1000 = Kilowatts
Electricity consumption is measured by the kilowatt-hour.
This is the amount of electrical energy
converted over one hour of time.
You can calculate kilowatt-hours using this formula:
Kilowatts x Time in Hours = Kilowatt-hours
Electricity costs vary by region, let’s use the prices shown in this sample electric bill from Southern
California Edison.
The baseline-summer line shows a cost of about 13 cents, or $0.13 per kWh
(kilowatt-hour).
You can
figure out the cost of a device by multiplying its electricity consumption in kWh by this cost.
Electricity Consumption(kWh) x Price($) = Total Cost
Use these formulas to determine the cost of each of these appliances of devices over a given period of
time.
1.
You wake up and unplug your cellphone from the wall socket.
A cell phone, while charging,
uses 2.6 watts/hour.
Assume it charged overnight (8 hours).
2.6 watts/hr /1000= .026kWh X .13kWh X 8hours=.027 or about 3cents charge a phone
overnight
The cell phone consumed 20.8 watt-hours of energy while charging overnight.
2.
You take out a bagel and place it in the toaster for 5 minutes.
The toaster uses 1050 watts/hour.
The toaster consumed approximately 87.45 watt-hours of energy while toasting the bagel for 5
minutes
3.
One of your classes at school takes place in the computer lab.
You work on an assignment for an
1
hour. The school lab has old desktop computers that use 100 watts/hour and large CRT (tube)
monitors that use 75 watts/hour.
The overall total energy consumed by the desktop computers and CRT monitors in the computer
lab during the hour of working on the assignment is 175 watt-hours.
4.
Arriving back from school, you decide to microwave a Hot Pocket for a snack.
You have a
1500W microwave that took 3 minutes to cook the Hot Pocket.
Microwave consumed 75 watt-hours of energy while cooking the Hot Pocket for 3 minutes.
5.
Noticing the sink full of dishes, you place them in the dishwasher and let it run for an hour and a
half (including the drying cycle).
Your dishwasher uses 2000 watts per hour.
Dishwasher consumed 3000 watt-hours of energy while running for an hour and a half, including
the drying cycle.
6.
You decide to relax for the night by playing video games on your Playstation 3.
You lose track
of time, and end up playing for 3 hours.
The PS3 uses 197 watts/hour.
You have an expensive
plasma TV that uses 339 watts/hour.
Playing video games on the Playstation 3 for 3 hours, along with using the plasma TV, consumed
a total of 1608 watt-hours of energy.
7.
Before going to bed for the night, you realize that you accidentally left the kitchen lights on all
day (12 hours).
The lighting fixtures in the kitchen have a total of 4 incandescent bulbs, each of
which uses 75watts/hour.
Leaving the kitchen lights on for 12 hours, with a total of 4 incandescent bulbs, consumed a total
of 3600 watt-hours of energy.
8.
What was your total electricity consumption (in kilowatt-hours) for the entire day?
How much
did this cost?
Approximately 8000 watts were consumed the entire day. The total cost is about $1040.
2
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