Lighting. Page: 6 of 17
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Dimmers for incandescent lights are relatively inexpensive
and generally have a one-year payback. In a restaurant,
for instance, a set of twelve 150-watt fixtures might be
dimmed 50 percent or more during the day. The graph
in Figure 2 shows that a savings of 75 watts per fixture
would save about $15/year per fixture or $180/year for
the room if electricity costs 5 cents/kWh. Thus a din-
mer which costs $100 installed would pay back in about
Dimmers are also available for fluorescent fixtures, but
multilevel ballasts are needed. This raises the cost and
extends payback by several years. Still, they can be an
excellent investment and should not be overlooked,
Cutting Down on Decorative Lighting
Decorative outdoor lighting is often overused. You
should decide whether it is essential to bathe your
building, trees and lawn in light. It is not necessary to
remove these lights; instead wire them to a manual
switch and only use them on special occasions. In some
cases outdoor lights are overgrown with shrubbery
which limits their usefulness. At one apartment build-
ing, sixteen 150-watt floodlights burned all night,
despite the fact they were completely overgrown by
juniper bushes. At an electricity cost of live cents per
kWh, turning these lights off saved the building owner
$500 per year.
Increasing Bulb & Fixture
Lighting efficiency is a measure of the light output
(lumens) vs the power used (watts). It is easy to measure
the efficiency of a bulb and to compare bulb efficiencies
such as is done in Figure 3. Actual lighting effectiveness,
however, is a function of bulb, fixture type and place-
ment, and room characteristics. We have already dis-
cussed the importance of light colored walls and ceilings.
In this section suggestions are made for improving bulb
and fixture effectiveness, as well as fixture placement.
This is a complex subject and we suggest you get profes-
sional help from a lighting designer if you want to go
beyond the basic recommendations in this booklet.
Relamping with High Efficiency Bulbs
It is possible to maintain the same light output but reduce
energy use by replacing existing bulbs with new high-
efficiency types. An inexpensive way to do this is to
switch to higher efficiency bulbs as burned-out bulbs are
replaced. Replacing incandescent flood lights with ellipti-
cal reflector (ER) bulbs in recessed fixtures saves as much
as 50 percent (Figure 4). Clear bulbs are preferrable to
frosted ones as they give off more light. Substituting a
100-watt bulb for two 60-watt bulbs saves 17 percent per
fixture. When relamping fluorescents, use energy-saving
I I I
100 200 300
WATTS SAVED PER FIXTURE REPLACED
(Based on 4000 operating hours/yr)
For example, if one 200-watt incandescent fixture is replaced with a two-tube
fluorescent fixture (two 32-watt tubes and a 10-watt ballast)
Watts saved - 200 - 74 - 126 watts Cost/hxture - $60
Dollars saved/yr v 05/kWh - $26 Payback - $601$26 2 3years
Figure 2: This graph allows you to estimate the annual
savings and payback from replacing fixtures or using
lower wattage bulbs,
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Figure 4: ER lamps deliver more light and use less
energy than incandescent bulIs.
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Administration., United States. Bonneville Power. Lighting., report, September 1, 1992; Portland, Oregon. (https://digital.library.unt.edu/ark:/67531/metadc1317287/m1/6/: accessed April 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.