COOPERATIVE EXTENSION SERVICE ● UNIVERSITY OF KENTUCKY
COLLEGE OF AGRICULTURE, FOOD and ENVIRONMENT ● LEXINGTON, KY 40546
When to Turn Off Your Lights
Source: Beverly K. Miller, Architect MArch, BArch, Senior Extension Associate
Photo: energy.gov
INCANDESCENT LIGHT BULB
CFL (COMPACT FLUORESCENT LAMP)
This type of bulb consumes a
lot of energy to produce
light, with most of the energy
consumed converted into
heat. It is the least energy
efficient bulb.
CFL bulbs use about onefourth the energy of traditional
incandescent bulbs. You can
buy CFLs with the same
brightness and colors as
traditional incandescent bulbs.
Some CFLs are encased to
provide a similar shape to
traditional incandescent bulbs.
Photo: Microsoft Clip Art, 2013
Photo: energy.gov
HALOGEN BULB
(ENERGY-SAVING INCANDESCENT)
LED (LIGHT EMITTING DIODE)
Halogen light bulbs are
about 25% more efficient
and can last up to three times
longer than traditional incandescent bulbs. They are
available in a wide range of
shapes and colors, and can
be used with dimmers.
LEDs are a new kind of light.
These bulbs offer similar light
quality to traditional
incandescent bulbs, last 25
times as long, and use even
less energy than CFLs.
Photo: energy.gov
Photo: energy.gov
HALOGEN LIGHTING
Halogen lighting is a type of
incandescent lighting. Halogen
light bulbs are more energy
efficient than a traditional
incandescent bulb. Halogen
light bulbs still use more
energy than CFL (compact
fluorescent lamp) and LED
(light emitting diode) light bulbs. Turn halogen light
bulbs off whenever they are not needed.
Photo: Microsoft Clip Art, 2013
When should I turn off a light to save energy?
This is an often asked question and like many energy
questions, the answer is, it depends. There are many
different types of light bulbs available. When to turn
off a light bulb, without reducing its life, depends on
the bulb type. It also depends on how long the light
will be off before you need to turn it on again. The
following facts about four common types of lighting
may help you determine when to turn off lights.
These facts may also provide guidance in
determining the type of light bulb to buy for different
home applications. An average household spends
about ten percent of its energy budget on lighting.
One of the fastest ways to reduce lighting costs is to
use energy efficient lighting.
For the greatest savings, replace old incandescent
light bulbs with ENERGY STAR-qualified light
bulbs.
FLUORESCENT LIGHTING
Fluorescent lighting is very
energy efficient. A CFL’s life
can be shortened by the
number of times it is turned on
and off. Since CFLs are very
energy efficient, prolonging
the bulb’s life is more
important than turning it off
for a short period of time.
To save energy and prolong the life of a CFL follow
these guidelines. Leave the light on if you will be out
of the room less than 15 minutes. Turn the light off if
you will be out of the room more than 15 minutes.
INCANDESCENT LIGHTING
LED LIGHTING
Incandescent lighting is
considered to be the least
energy efficient type of
lighting. Incandescent lights
should be turned off whenever
they are not needed.
LED, or light emitting diode,
lighting is very energy efficient
and even more efficient than
fluorescent lighting. The
operating life of LEDs is
unaffected by turning the light
on and off. LEDs turn on at full
brightness almost instantly.
They are largely unaffected by vibration because they
do not have filaments or glass enclosures.
Incandescent light bulbs use
only 10% of the energy they consume to produce
light. Approximately 90% of the energy consumed by
this type of light bulb is given off as heat. During the
summer cooling season, you should limit the use of
incandescent lighting. This will keep your room
cooler and save on air conditioning costs.
LED lighting works well with occupancy sensors and
daylight sensors because their life span is not affected
by frequent switching.
Educational programs of Kentucky Cooperative Extension serve all people regardless of race, color, age, sex, religion, disability, or national origin. Issued in furtherance of Cooperative
Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, M. Scott Smith, Director, Land Grant Programs, University of Kentucky College of
Agriculture, Lexington, and Kentucky State University, Frankfort. Copyright © 2013 for materials developed by University of Kentucky Cooperative Extension. This publication may be
reproduced in portions or its entirety for educational or nonprofit purposes only. Permitted users shall give credit to the author(s) and include this copyright notice. Publications are also
available at www.bae.uky.edu/energy/residential.