EGEE 102
Energy Conservation for Environmental Protection

Review and Extra Resources


Review Sheet Lesson 9 – Home Cooling

  • Humidity
  • Relative Humidity- simple calculation of RH
  • What happens to relative humidity when the temperature of air changes
  • Air Conditioner
    • Operating principle of Air Conditioner
    • Components of air conditioners – What happens at each component?
    • Types of air conditioners, which ones are more efficient?
    • Terms used to measure efficiency (EER and SEER) and their meaning
  • Factors affecting the size of a room air conditioner
  • Energy Savings
    • Natural Cooling
    • Payback period calculation using EER
  • Tips for efficient AC operation and saving money

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!

Short Answer Questions

  1. Define Relative Humidity.
  2. Explain with a sketch, the four main components of an air conditioner and their function.
  3. List the two main types of central air conditioner systems, and explain the difference between the two types.
  4. What are the main factors to be considered in sizing a room air conditioner?
  5. What are natural (passive) ways in which you can reduce your cooling costs?
  6. Define EER and SEER.

Problems for Practice

  1. A contractor says the home requires a 5 ton air conditioning system. How many BTUS does this system pull out each hour?
  2. John Jankomsky has an air conditioner that is rated at 10,000 BTUs/h with an EER of 10. What is the power consumption of the air conditioner?
  3. Your old high school pal, Mike Errington, wants to upgrade an old 1976 vintage room air conditioner that is believed to operate at an EER of 5.5. He is considering a room air conditioner with an EER of 11. He wants to know by what percentage his electricity consumption would reduce. Can you help him with the data given, or not?
  4. Suppose you are comparing two air conditioners, both of which last for 10 years. The least efficient air conditioner draws 775 W of power. The most efficient one uses 700 Watts. Assuming that the air conditioner operates 2,000 hours annually and that the local energy cost is 0.09 per kWh, can you save any money and energy with the energy efficient model? If so, how much?  If the energy efficient model costs $50 more than the least energy efficient model, would you buy the more energy efficient model? Justify your answer quantitatively.

Extra Resources

For more information on topics discussed in Lesson 9, see these selected references:

  1. How Stuff Works
  2. Comfort, Air Quality, and Efficiency by Design, Manual RS, Air Conditioning Contractors of America (ACCA), 1999. 80 pp.
  3. Cooling and Heating Load Calculation Principles, American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. (ASHRAE), 1998. 248 pp.
  4. Bob Villa
  5. Cooling Your Home Naturally, US Department of Energy report, CH10093-2221-FS 186, 1994, 8 pp.
  6. Energy Efficient Air Conditioning, US Department of Energy report, CH10099-379-FS 206, 1999, 8 pp.
  7. Cooling Your Home with Fans and Ventilation, US Department of Energy report, DOE/GO-10200101278-379-PS 228, 2001, 8 pp.
  8. Energy Star