Name ______
ACTIVITY: Home Appliances and BHU Calculations
C. Schneider Mar 2006, T. LaHue Jan, 2007, P. Seales 2008,9,12
1. Talk to your family about usage of major electric appliances in your home and find the AGE of your fridge ______,
type of clothes washer top/front loader, TV size and type
(Also find out the average electric bill/month ______and list the # of people ______)
You MUST include refrigerator, clothes washer & drier, heating/cooling equipment, stove, TV, DVD/VCR player, computer.
Count light bulbs. - We will assume that everyone has an "all electric" home - this makes the calculations simpler.
2. Write down the number of hours per day / month that the each appliance is used. Assume 30 days per month.
3. If possible write down wattage of each appliance. It should be written on the bottom or back of the appliance.
If you find the plug has voltage and amps use power (watts) = voltage x amps
If you can’t figure out the wattage write down approx. purchase year - see teacher list of generic values
4. Calculate the kilowatt-hours by multiplying the wattage x hours/month ÷ 1000
5. Find the highest user of energy in your household and then rank all ten using 1 for the highest
APPLIANCES/TYPE or YEAR / WATTAGE / HOURS/DAY of use / HOURS/
MONTH / kWh used
/MONTH / RANK
Refrigerator year ______
Clothes Washer
Clothes Drier
Furnace
TV
Computer
Light bulbs / STD
Light bulbs / CFL
TOTAL / XXXXXX / XXXXXXXX / XXXXXX / XXXX
6. Find the cost /month by getting the total kWhr and multiplying the kilowatt-hours by the rate of $0.2 /kWhr
Total Electrical Energy Cost/month =
Follow-Up
1. Do you have any new ENERGY STAR appliances? ______How old is your Fridge? ______
2. Consult reference sheet A plasma TV can use ______watts , whereas a std 36" uses ______watts
Calculate the difference and use your hours /month to find the EXTRA in kWHrs /year
3. Consult reference sheet. An older fridge uses ______watts , whereas a new energy star uses ______
Assume it's always on and calculate the saving in kWHrs /year if you switch to a new fridge
Energy Problems with BTUs Derived from AP Board "Energy and Climate Change"
Units and Conversions
1 calorie is the amount of heat required to raise 1g of water by 1 C degree.
1 kcalorie would increase the temperature of 1 kg of water by 1 C degree ; 1 kcal = 4.12 kJoules
1 Btu is the heat required to raise 1 pound of water by 1 degree
1 Btu = 252 cal = 1055 J; 1ccf = 100 cubic foot of gas;Gas energy is 1000Btu/cf
Practice Question
1. a. Given that 1 kWh = 3.6 MJ and that 1 Btu = 1055 J, show that 1 kWh = 3412 Btu.
Do these Without Calculators - Round and Estimate !!!
2. a. How many kcals would be required to heat 100 kg of water by 20°C for a bath?
b. How many joules is this? c. How many Btus?
d. If your water heater can supply 40 kBtu/h, how long will it take to heat this water?
3. A typical home in the northern U.S. requires 120 MBtu of heat for the average winter.
a. With a natural gas furnace , 60 % efficient, how many cubic feet of gas would be needed?
b. At a cost of $0.90/ccf, what would it cost to heat this house for one season?
c. If a new 80 percent efficient furnace cost $4,000, how long would it take to pay back the cost assuming gas prices remained the same?
4. Suppose the house in question 3 is in Cleveland with average solar flux -160 W/m2.
If 10 m2 of solar panels - 20 % efficient - were installed to collect solar energy as hot water:
a. How much energy could be gained in one year in this manner?
b. What fraction of the annual heating requirement is this?
c. Using the hot-water heating requirements for a bath from question 1(c), how many hot baths would this energy supply in one year?
d. If a family of 4 each took a bath every day, how much energy would be saved per year by switching to SHORT showers - only 10kg of hot water
Typical Wattages of Various Appliances
Aquarium = 50–1210 Watts
Clock radio = 10
Coffee maker = 900–1200
Clothes washer = Older top loading 350–500, *New front loading 100
Clothes dryer = Electric (gas) 1800–5000 *LINE Drying = 0
Dishwasher = 1200–2400 (using drying feature magnifies energy use)
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 = 750–1300
Personal computer
CPU - awake /"power saver"/ asleep = 120 / 60 / 30 or less
Monitor - awake / asleep = 150 / 30 or less
Laptop = 50
Radio (stereo) = 70–400
Refrigerator (frost-free, 16 cubic feet) = Pre 1990 - 725
**New Energy Star = 150
Televisions (color)
19" = 65–110, 27" = 113, 36" = 133
53"-61" Projection = 170
Flat screen = 120
! Plasma 60" = 600
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 (with heater, no cover) = 120–380
HomeApplBTUs1/13/19