Review and Extra Resources

Test Yourself

The questions below are your chance to test and practice your understanding of the content covered in this lesson. In other words, you should be able to answer the following questions if you know the material that was just covered! If you have problems with any of the items, feel free to post your question on the unit message board so your classmates, and/or your instructor, can help you out!

1. Describe three operating practices in using refrigerators that can save energy and money.
2. List the five main components of a refrigerator, and explain how a refrigerator works.
3. Describe five ways in which you, with good operating practices, can reduce energy consumption of water heaters at home.
4. Explain the advantages and disadvantages between Storage and Demand water heaters.
5. What are the various methods in which solar energy can be collected for water heating?
6. What is EF? And how does it describe the efficiency of a water heater?
7. How do electric and gas compare for water heating?
8. Why are ENERGY STAR appliances better in terms of efficiency, and how can they help the environment?
9. What are Energy Guide Labels? What information can be obtained from these labels, and how can this information can be used to select an environmentally friendly appliance?
10. Briefly describe five ways in which we can save energy in using clothes washers and dryers.
11. Compare and contrast the v-axis (top loading) and h-axis (front loading) water heaters.
12. Explain how energy efficiency of clothes washers is evaluated.
13. What are good operating practices for clothes dryers?
14. How can you describe the energy efficiency of dishwashers?
15. Describe appliance-operating practices that can help the environment.
16. Calculate the amount of heat energy required to heat 200 lbs of water that is heated from 55 degrees F to 130 degrees F.
17. 200 gal of water is heated in a heater from 60 degrees F to 120 degrees F every day by a family of four. What is the annual energy requirement?
18. An electric water heater heats 250 gallons of water per day from 58 degrees F to 140 degrees F. How many kWh of energy are required? Recall that, 3412 Btus =1 kWh.
19. If the temperature of the water heater was reduced to 120 degrees F, what percent of energy can be saved?
20. What is the cost of operating the water heater in Problem 3, if electricity cost is $0.08 per kWh?
21. A water heater heats 200 gal of water a day from 55 degrees F to 130 degrees F using natural gas. How many CCF of natural gas are required every month?
22. What would be the monthly cost of natural gas in problem 6?
23. What would be the monthly cost of energy if electricity was used for heating the water in problem 6?
24. If the temperature of the water heater was reduced to 120 degrees F in Problem 6, how many kWh could be saved and what would be the cost savings?
25. Estimate the % energy savings of an electric water heater that heats 100 gallons per day when the temperature is set back at 110 instead of 120 F. The basement is heated and is at 65 F. The life of the water heater is expected to be about 15 years.
    • Use an appropriate cost for electricity, and compare the operating expenses with the approximate initial cost of the water heater (from the lectures).
    • Heat required (BTUS) = m x Cp x (Temperature Difference)
    • Where Cp is the heat capacity of water (1 Btu/lb/F)
    • And m is the mass of the water (Assume 1 gal has 8.3 lb of water and the 3,412 Btus = 1 kWh)
26. An old refrigerator consumed 150 W of power. Assuming that the refrigerator operates for 20 hours in a day, what is the annual operating cost, assuming the cost of electricity to be $0.06 per kWh?
27. Suppose that an oven lasts for 10 years. For a given heating effect, the least efficient oven draws 1,000 W. The most efficient one uses 450 Watts. Assuming that the oven uses 700 W annually, and that the local energy cost is 0.06 per kWh, can you save any money? If so, how much money over its lifetime? If the more efficient oven costs $100 more than the least efficient one, would you buy the more efficient model?
28. Suppose you are comparing two refrigerators, both of which last for 10 years. The least efficient refrigerator draws 275 W of power. The most efficient one uses 250 Watts. Assuming that the refrigerator operates 4000 hours annually and that the local energy cost is 0.06 per kWh, can you save any money with the energy efficient model? If so, how much money over its lifetime? If the more efficient refrigerator costs $100 more than the least efficient one, would you buy the more efficient model?