EGEE 102
Energy Conservation and Environmental Protection

Review and Extra Resources


Watch the 5:25 Lesson 5 Review below.

EGEE 102 Lesson 5 review
Click Here for Transcript of Lesson 5 review video

Here are two different models and come up with a energy savings as well as money. You should be able to calculate or perform a life cycle analysis or calculate annual energy savings. And this is actually demonstrated or illustrated on pages 279 and 280 of the textbook. Basically, if you have a model A and model B, you should be able to compare the initial prices of these two amounts of energy consumed and how long will it take to recover the initial extra costs that you will be paying for energy efficient model, and also, how much energy it saves over its lifetime or per year, and how long will it take to recover the investment, which is the payback period. And this can be done using life cycle analysis, like purchase price plus energy costs over its lifetime plus maintenance costs, if there are any. This constitutes the total life cycle cost, which means what you would incur for purchasing it, maintaining it, and also supplying the energy to use that appliance. And whatever the costs that you get from model A and model B, whichever is cheaper, that tells us whichever one is economical. So I want you to do this for two or three different types, refrigerators, or if the data is given for refrigerators, water heaters, and so on. You should be able to do the life cycle analysis and tell me which one is more energy efficient, in the long run, which one saves more money. And when it comes to specifically to water heaters, you should be able to calculate energy required to heat the water using the equation, mCp delta T. This is the equation. m is the mass of water that we are heating. Cp is the heat capacity. And delta T is the temperature difference from which temperature to which temperature you're heating water. And this gives us the energy, and also, to bind the same amount of energy, whether gas would cost more or electric would cost more. You may want to look at that, and of course, the description, the types of water heaters, advantages and disadvantages of all these different types. And most importantly, in all these appliances part, you should be looking at energy efficiency, how we measure energy efficiency. For example, water heaters, we use energy factor. What is it, actually? You need to know and be able to compare one or two and determine which one is more efficient, and what we can save to save energy, what we can do to save energy with respect to water heaters, setting the temperature lower, or turning off when we are on vacations, and so on, and so forth. You need to understand what we are doing with that. When it comes to refrigerators, I want you to focus on four different components that go into refrigerators, how a refrigerator works, basically using these four components, and the function of each of these-- what does an expansion valve do, what an evaporator does, and what a compressor does, et cetera. And we have three types of refrigerator-- top mounted, bottom mounted, and side-by-side. Which one is more efficient? And why is it more efficient, for example? Bottom mounted should be the most efficient because the cold stays at the bottom and warm places. So top mounted is not that efficient compared to bottom mounted. And side-by-side is not efficient. But if you've ever have to buy side-by-side, which most of us do these days, you have to go for energy efficiency or Energy Star models, which typically exceed the federal requirements. And what you can do to reduce energy consumption of refrigerators, that's something that you may want to look at the tips that you can follow. And clothes washers. Front loading, top loading, which one is more efficient? Front loading is more efficient because clothes are lifted and dropped continuously. And that cleans the clothes also very well. And you need to know the difference between energy factor, water factor, and modified energy factor. Look at the textbook for more description of these things or look at the notes online. And you need to know the difference between those three, actually, and how to calculate those things. And clothes dryer are pretty simple-- energy efficiency, how we monitor. And what is the operating principle of your dishwasher?

Review Sheet Lesson 5 – Appliances

  • Appliance energy consumption
  • Use Energy guide labels
    • Should be able to calculate/perform
      • Annual energy savings when comparing two models
      • Payback period when comparing two models
      • Life cycle analysis when comparing two models
  • Water heaters
    • Should be able to calculate energy required for heating water
    • Gas vs. electric
    • Types of water heaters (advantages and disadvantages)
      • Storage or tank
      • Type on demand
      • Heat pump
      • Tankless coil
      • Indirect
      • Solar
    • Energy Efficiency of water heater
      • Energy Factor (EF)
    • Environmental protection
  • Refrigerators
    • How Does a Refrigerator Work? Function of:
      • Expansion valve
      • Evaporator
      • Compressor
      • Condenser
    • Types of refrigerators
      • Top Mounted
      • Bottom Mounted
      • Side-by-side
    • Energy Efficiency
    • Environmental Protection
  • Clothes Washer
    •  Types
      • Horizontal Axis (front loading)
      • Vertical Axis (top loading)
    • Efficiency
      • Energy Factor (EF)
      • Water Factor (WF)
      • Modified Energy Factor (MEF)
    • Environmental Protection
  • Clothes Dryer
    • Energy Efficiency
    • Environmental Protection
  • Dish Washer
    • How a Dishwasher works
    • Environmental Protection

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?

Extra Resources

For more information on topics discussed in Lesson 5, see these selected references:

  1. ACEEE Heating
  2. Office Energy efficiency
  3. Elements of an energy efficient house
  4. Fiber Glass Loose Fill Insulation
  5. Q&A About Home Insulation
  6. Energy Savers - Insulation