8.11 Lighting Review

EGEE 102 Lesson 8 Review

Throughout this lesson, you've learned that lighting is more than just flipping a switch—it's a critical component of energy use in homes, schools, and businesses. Here's what matters most:

Not all light is created equal: Incandescent, halogen, fluorescent, HID, and LED lamps produce light in different ways—with vastly different impacts on energy use, cost, and the environment.

Lumens measure light; watts measure energy: When choosing a lamp, compare lumens (brightness) and lumens per watt (efficiency)—not just wattage. LEDs deliver the most light for the least energy.

Smart design saves energy: Matching the right light level (foot-candles) to the task—whether reading, highlighting art, or walking down a hall—prevents waste. Simple calculations help you determine exactly how many lumens (and lamps) you need.

Color matters: The Color Rendering Index (CRI) affects how true colors appear. For tasks involving color judgment, choose high-CRI lamps (90+), now widely available in LED options.

Controls multiply savings: Switches, timers, photocells, motion sensors, and dimmers ensure lights are used only when and where needed—cutting energy use without sacrificing comfort.

Think long-term: Life-cycle cost analysis reveals that the cheapest lamp upfront isn't always the cheapest over time. LEDs typically offer the lowest total cost through energy savings, longevity, and reduced maintenance.

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. How is light measured?
2. What factors determine the amount of light that is needed in a room?
3. What are the three main methods of producing light?
4. Explain the difference between incandescence, fluorescence, and high intensity discharge.
5. What are the common ways in which we can improve energy efficiency?
6. A 60-watt light bulb produces 3 watts of radiant energy and 57 watts of heat energy. What is its efficiency?
7. A 13-watt lamp is left on all day (24 hours). How much did it cost to operate the light bulb if electricity costs 15 cents per kWh?
8. A 100 watt incandescent light bulb is operated for 12 hours, and a 15 watt fluorescent light bulb is operated for the same period of time. At 18 cents per kWh, what are the cost savings of the fluorescent bulb?
9. Jackie Smith, who is very conscious about the environment, would like to know how much energy she can save by switching to LED lamps. Estimate the total energy savings for Jackie, who uses a light bulb fixture, by comparing the total costs to own and operate an 8-Watt LED instead of the 60 Watt incandescent bulb that she has been using. The expected life of incandescent and LED bulbs is 1000 h and, 18000 hours. The purchase price of an incandescent bulb is $0.50 and the LED is $2.50. If Jackie Smith replaces 24 bulbs at home with LEDs, what would her savings be if the electricity cost is $0.185 per kWh?