Unit: Matter, Energy, and Ecosystems
Part 1: Calculating operating cost for an appliance
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- Your Electric Meter
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Part 1: Calculating operating cost for an applianceIn 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 $.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: ______________ power =________watts or current =______ amps 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. 6. Repeat the process for a different type of appliance. Show your work below (with units!) 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. The report comes in FOUR parts (A, B, C, D). Your Electric MeterRead 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. TAKE A PHOTO OF THE METER 2. 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. USE THE DIAGRAM ON THE NEXT PAGE. DIALS: 1. Reading = _________________ kWh Time: ______________ ; Date: ________________ B. NORMAL USAGE (one week later)- 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. 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 approximately 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
5. Energy saved if 10% of the households in the United States did the same for one year 6. 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? 7. Lbs of CO2 saved if 10% of the households in the United States did the same for one year. 8. How did the changes affect your family and would you consider maintaining these changes?
Show all calculations with units1. 3.2 tons of coal is used to provide enough heat to bring the temperature of 2.0 x l05 gallons of water up 300 F. The heat value of one ton of coal is 2.5 x107 BTU/ton. One gallon of water weighs 8 lbs and BTU’s are calculated by multiplying pounds of water by their change in temperature in degrees Fahrenheit. a. What is the input energy? b. What is the useful energy (output)? c. What is the efficiency?
2. A cord of wood is used in a wood stove/fireplace to heat a house. If the transfer from the wood to the house is 70% efficient, how much heat will be delivered? The heat in a cord of wood is 2.0 x 107 BTU. b. Where did the waste energy go? Look at a fireplace to figure this out. 3. a. Natural gas, with the heat content of 1030 BTU/ft3 is used to produce electricity. If 4.5 x 106 ft3 of natural gas is used, and the conversion is 65% efficient, how many kWh of electricity can be generated? One kWh = 3413 BTU. b. If the electricity produced above is used to power an electric stove that has 79% efficiency, how many BTUs can be delivered by the stove? Swimming Pool Energy Worksheet Directory: file -> view view -> Western Europe after wwii view -> Author study: paul fleischman view -> Qpa1 7ela study Guide view -> Arctic Oil/Gas Neg view -> November 1970 Approximately 150,000-500,000 deaths Bhola Cyclone Bangladesh view -> Grade Level: 6 Unit of Study: Caribbean glce view -> Citation: Duffield, Katy view -> Table of Contents Lesson # view -> Chinese Wind Energy Disad Download 0.59 Mb. Share with your friends:
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