Michigan
State University Extension
Home Maintenance And Repair
06/24/03
Energy Tips - Energy Efficient Lighting
With
the steady rise in energy prices, many people are making a conscious
effort to reduce their energy consumption. One of the easiest ways to
lower energy consumption is to use energy efficient lighting. Energy
efficient lamps and fixtures can be installed in all buildings
including homes and businesses as well as outdoors.
The initial cost of installing the energy efficient lighting may be a
bit unsettling at first. But with some simple calculations, it's easy
to see that switching to more efficient lighting will save money and
you may be able to see your return much sooner than you think.
Getting started
Before changing lamps and fixtures to energy efficient ones, it
is important to evaluate your current lighting system. Changing to the
wrong type of fixture could give too much or too little light or give a
room poor color rendition. These factors are especially important in
retail stores and office buildings. Another important consideration is
the type of lamp or light fixture for the application. Some lamps like
fluorescent operate poorly in cold or moist areas. Before purchasing a
fixture or lamp, read the installation instructions and make sure it
suits your needs.
T-8 Fluorescent lighting
T-8 fluorescent lighting is a relatively new technology. At
first glace it looks like any standard fluorescent fixture. Closer
inspection shows an electronic ballast powering smaller diameter lamps
that makes the fixture up to 75% more efficient. Two options exist for
those who want to switch to T-8 lighting. If a fluorescent fixture
exists, it can be retrofitted inexpensively with a T-8 ballast and
lamps. New T-8 fixtures are available and can be purchased in different
styles to meet most lighting requirements.
Compact Fluorescent Lamps (CFL)
Compact fluorescent lamps (CFL) are the easiest and, in many cases, the
least expensive way to switch an existing lighting design to energy
efficient lighting. CFLs combine a fluorescent lamp and ballast into a
lamp roughly the same size as a standard incandescent lamp. Most of
these lamps have bases that screw into a standard light socket and this
eliminates the need to change wiring or to hire an electrician. These
lamps are sold with an equivalent incandescent wattage. An example
would be a 15-watt CFL that gives off an equivalent amount of light to
a 75-watt incandescent lamp. Another advantage of the CFL is its longer
lamp life. An incandescent lamp will last from 750 to 2,000 hours of
operation while a CFL will last 10,000 to 20,000 hours.
Important fluorescent lighting notes (tubular and CFL types):
• Fluorescent fixtures including CFLs are not dimmable unless
they are purchased specifically for that purpose.
• Fixtures need to be enclosed when used in agricultural buildings.
• They lose efficiency in cold temperatures (for low temperature
operation, use jacketed lamps or an enclosed fixture and use low
temperature ballasts).
• Lamp life is shortened by frequently turning it off and on.
High Intensity Discharge (HID) Lighting
In the right applications, high-intensity discharge (HID) lamps
have overwhelming advantages over incandescent lamps. A measure of the
output of a lamp is the number of lumens. Efficiency is given in lumens
produced per watt consumed. While incandescent lamps have an efficiency
of more than 12 lumens per watt, HID lamps can produce up to 198 lumens
per watt.
HID fixtures come in four basic types.
• high-pressure sodium
• low-pressure sodium
• mercury vapor
• metal halide
Choosing which HID fixture is best to use depends on your intended
application.
For use as a security light only, low-pressure sodium is the
most efficient and has the longest life, but colors will not appear
normal. For good color and high efficiency, use metal halide. The
initial purchase price is significantly higher than that of the
low-pressure sodium. Mercury vapor lamps and fixtures are inexpensive,
but their efficiency is the lowest of the HID sources. High pressure
sodium has high efficiency, but it produces an excess of orange light.
It is important to remember that HID fixtures are designed to work with
specific lamps. Using the wrong lamp could cause damage to the lamp and
fixture.
HID notes
• They work well in all temperatures.
• They have a slow warm-up and restrike time. When turned off, they
don't come back on for one to five minutes depending upon the type.
• Consider putting an incandescent fixture with a photocell to provide
light in the event that there is a power interruption followed by a
slow restrike time.
• Choose a lamp according to color requirements
Initial Investment vs. Annual Savings
One of the main arguments against retrofitting to energy
efficient lighting is the cost of switching lamps and fixtures. For
example, a compact fluorescent lamp can be 24 times more expensive than
a standard incandescent lamp. While it is initially more expensive to
switch, a simple calculation will show the total cost of operation over
the life of both lamps and show the total amount saved.
This example compares the operating cost of a 25-watt compact
fluorescent lamp and a 100-watt incandescent lamp both operating 2,500
hours a year and both having the same light output. The energy cost
used is $.10 per kilowatt hour.
Compact Fluorescent Lamp
2,500 hrs X 25W X $.10
= $6.25 Per year
1,000
Incandescent Lamp
2,500 hrs X 100W X
$.10 = $25.00 Per year
1,000
Energy Savings per year: $18.75
In this scenario, the cost of the CFL would be paid for in the
first year. Another aspect to consider is the number of lamps used
during this period of time. In the previous example, the CFL lamp life
was 6,000 hours and the incandescent lamp life was 750 hours. Within
the 2,500 hour period of time, the incandescent lamp would have been
changed at least three times, while at the same time, the CFL would
have only reached half of its life expectancy. While there is an energy
savings in this instance, keep in mind that energy efficient lighting
only saves money while energy is used. In the case of a closet, storage
room, or other such area where lights are used only occasionally, it is
more cost effective to use incandescent lighting.
Other Methods
The use of occupancy sensors is another good way to conserve
electricity. An occupancy sensor detects movement of heat within an
area (such as a person walking into a room) and turns the lights on.
When a person leaves the room, a timer counts for a set number of
minutes and turns the light off. This is ideal for rooms where the
lights are frequently left on. There is also switch that allows the
light to be manually turned on and off. These sensors come in a number
of styles including a ceiling mounted unit, a unit that mounts in place
of a standard light switch, and a unit made to be mounted outdoors.
Dark colors in a room will absorb light and will require more light
fixtures to maintain the desired lighting level. The use of light
colors on wall and ceiling surfaces greatly reduces the number of light
fixtures needed and cuts energy consumption.
Lighting dimmers should be used only in areas where lighting levels
need to be changed. Dimmer switches are solid-state electronic devices
that consume energy even when they are at full intensity. An
alternative to using dimmers is to use multiple fixtures on multiple
switches. Turning the switch on or off can change lighting levels.
Energy Star
It is a good idea to make sure your energy efficient lamps and
fixtures meet or exceed Energy Star requirements. Energy Star is a
cooperative effort among the
Environmental Protection Agency, the Department of Energy, and industry
that sets standards for energy efficiency. In lighting these standards
include lamp life and light output.
An important safety note: make sure that devices you use are listed by
testing labs like UL, ETL, or CSA. Testing laboratories set reliability
and safety standards that must be met before their symbol (UL, ETL,
CSA) can be displayed on the product.
Safety notes
• Be sure to check with local code authorities before attempting
to install wiring and electrical devices.
• Make sure all wiring is installed in accordance with the National
Electrical Code®.
• Read and understand manufacturer installation instructions before
installing wiring and fixtures.
• When changes in wiring are required, it is recommended that a
licensed electrician make them. MSUE gratefully acknowledges the
expertise and experience of the author of this fact sheet on energy
efficient lighting systems.
Andrew Mayville
Electrical Technology Apprenticeship Program
Michigan State University
114 Farrall Hall
East Lansing, MI 48824
http://www.egr.msu.edu/age/ET/
Glossary
Compact Fluorescent Lamp (CFL) - newer, highly efficient lamps
that screw into existing light bulb sockets (in most cases) and
resemble traditional bulbs in appearance rather than the tubular style
of regular fluorescent lamps.
Fluorescent lamp- a tubular electric lamp having a coating of
fluorescent material on its inner surface and containing vapor whose
bombardment by electrons from the cathode provides ultraviolet light
that causes the material to emit visible light.
High Intensity Discharge lighting (HID) - formerly outdoor or
special use lights that now are being produced for indoor use; HID
greatly increases the
amount of light produced.
Incandescent lamp- an electric lamp in which a filament gives
off light when heated to incandescence by an electric current
(incandescence means white,
glowing, or luminous with intense heat).
Lamp- "light bulb"
Lumen- a unit of luminous flux equal to the light emitted in a
unit solid angle by a uniform point source of one candle intensity.
Restrike Time- the time it takes for a lamp to reach full
brightness when the lamp is first turned on; or if the lamp is burning,
the time it takes for the lamp to restrike when power is switched off
and then back on.
References
Energy Tips - Energy Efficient Lighting, Michigan State University
Extension E2802
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