LIGHTING AND APPLIANCES: Lighting
Questions:
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.
