LIGHTING AND APPLIANCES: Lighting

Questions:

• Are $10 compact fluorescent lamps cost-effective?
  
• What is the best exterior lighting source?
  
• Are mercury yard lights efficient?
  
• Can a photocell be installed on my outside lamp?
  
• Does it cost more to turn a light on and off rather than just leaving it on?
  
• What are the advantages of halogen lamps compared to regular incandescent lamps?
  

Are $10 compact fluorescent lamps cost-effective?
Yes, cost-conscious consumers know these lamps can save energy and money, and they last a long time.

A standard, 60-watt lamp lasts only about 1000 hours. A 15-watt compact fluorescent lamp with the same light output will last more than 10,000 hours and use much less electricity. To get 10,000 hours of use from a standard incandescent lamp, it would take 10 light bulbs at about 50 cents each that would consume more than $40 in electricity, a total cost of more than $45. By using a compact fluorescent, the lamp cost might be $10, but it would use only about $10 worth of energy for a total cost of $20.

These lamps are best used in fixtures that get used a lot or where the lamps are difficult to change.

What is the best exterior lighting source?
The best type of lighting depends on the desired use.
For example, low-pressure sodium lamps have the highest lumen per watt output (amount of light produced per watt of energy consumed) out of all light sources. However, the distinct yellow color of low-pressure sodium lamps limits their use to area lighting, such as parking lots and security lighting.

High-pressure sodium lamps have improved color. They are not as efficient as low-pressure sodium lamps but are still effective light sources and are well suited for general-purpose lighting, parking, or as street lamps.

Metal halide lamps are the preferred light source for outdoor sports activities. The light produced by these lamps has good color and looks more natural than the yellow light of sodium lamps. The output and efficiency of metal halides is lower than either of the sodium lamps but much improved compared to the less expensive mercury vapor lamps.

Are mercury yard lights efficient?
Mercury vapor lamps are more efficient than incandescent lamps, but to substantially improve the efficiency of outdoor lighting, use high-pressure sodium lamps.

Lighting efficiency is a measure of the amount of light from a lamp, in lumens, divided by the power to the lamp, in watts. A 100-watt mercury lamp has an efficiency of 38 lumens per watt. The efficiency of an incandescent lamp is about 16 lumens per watt.

Sodium lamps producing about the same light as a 100-watt mercury vapor lamp have an efficiency of 70 lumens per watt, more than four times more efficient than incandescent lamps, and twice as efficient as mercury vapor.

The smallest sodium lamp is a 35-watt lamp. It will produce more light than a 100-watt incandescent. It takes about five minutes for a sodium lamp to brighten, so they shouldn't be used where they will be turned on and off frequently.

Can a photocell be installed on my outside lamp?
Yes, a photocell can be installed. The switch is about $20. It should be mounted near the lamp but in a location where the light won't shine on the sensor.

Does it cost more to turn a light on and off rather than just leaving it on?
Turning lights off when they are not needed will always save energy. The momentary power surge caused by turning a light on is so small and so brief, it won't even register on a electric meter.

However, frequent switching of fluorescent lamps will shorten their life, eating into the savings of turning them off. Even so, fluorescent lamps need only be off a short period of time for the energy savings to exceed the cost of reduced lamp life. Thus, if planning to be out of a room for more than about 15 minutes, shut fluorescent lamps off.

Practically speaking, incandescent lamps are not affected by frequency of switching. Shut them off whenever they are not needed, no matter how short the time period.

What are the advantages of halogen lamps compared to regular incandescent lamps?
Halogen lamps have a longer life, better color and the light output does not depreciate with lamp age.

Traditional incandescent lamps darken with age. Halogen lamps employ a special gas mixture, higher temperatures, and special glass to improve lamp life and eliminate lamp darkening.
In addition to longer life, halogen lamps offer very clean, bright white light, especially useful for retail display. The lamps are also used in reading lamps or other applications where light quality is important. However, halogen lamps do not have a second glass envelope that limits bulb surface temperature. Therefore they should be used with extreme caution. Bulb surface temperatures of up to 1,100 degrees Fahrenheit are possible.

Some halogen lamps are slightly more energy efficient than regular incandescent lamps. However, if lower operating costs are the motive, consider using compact fluorescent lamps. Several manufacturers have announced plans for an energy-efficient torchiere. Contact EPA Energy Star at (202) 233-9841 for a list.