Lighting has been one of the great success stories in
energy efficiency of the last quarter of the 20th Century.
And it could become another great success story of the next
few years as we proceed further into the 21st Century.
During the years following the oil crises of the early 1970s,
commercial building owners and managers reacted to high electricity
prices by retrofitting offices, warehouses, and stores. First
they turned to reducing unnecessarily overlit areas, and later
they installed new lower wattage fluorescent tubes and electronic
ballasts. As a result, energy use for lighting in the commercial
sector fell even as the number of commercial buildings rose.
Now the success in the commercial sector may be a prelude
to another great energy efficiency success--this time in
the residential sector. The compact fluorescent bulb is
the key that could unlock this success.
Like the fluorescent lamps found in commercial buildings,
a compact fluorescent bulb is a tube. These tubes, however,
are narrower and twisted around like a pretzel. Sometimes
they are covered with a globe so that they look much like
a standard incandescent bulb.
The big difference between compact fluorescents and their
incandescent cousins is the amount of energy they use. Compact
fluorescents use roughly one-quarter of the electricity
that an incandescent bulb will use to give off the same
amount of light. Of course the exact difference in light
output will depend on how the tubes are shaped, whether
it has a cosmetic globe, and a number of other minor things.
But cutting the electricity use of a light by anywhere near
75% is a lot of savings. Below is a table of typical compact
fluorescent bulbs and their equivalent incandescent bulbs.
Compact
Fluorescent
Bulbs
|
Incandescent
Bulbs
|
|
7 watts
|
25 watts
|
|
15 watts
|
60 watts
|
|
18 watts
|
75 watts
|
|
27 watts
|
100 watts
|
|
32 watts
|
150 watts
|
Now the difference between a light using 60 watts and
one using 15 watts may not inspire dreams about how you
will spend all the money that you will save. But look around
your house. You may see the light!
When I looked around my house, I realized that there are
four places in my house where lights are generally on more
than 3 hours each day: the kitchen, the living room (where
we watch TV), the parlor (where the kids do their homework),
and the porch. In the winter, the lights in these rooms
are usually on much more than 3 hours each day. Moreover,
with the exception of the porch, more than one bulb is burning
in each of these rooms when they are being used.
You should know two other things about compact fluorescents.
First, they cost a good deal more than incandescents. And
then, they last much longer than incandescents. (If you
think there's an economics problem coming up, you're right.)
Why should you care which lights stay on the longest in
your house? Replacing all your incandescents with fluorescents
would certainly reap large energy savings, but it would
require a bit of an investment. Compact fluorescents usually
cost between $5 and $15 per bulb. Since incandescents can
often be purchased for 50 cents, that difference is quite
significant. I can usually find compact fluorescents of
high quality at my local hardware store for around $10.
If you shop on the Web and are willing to buy 10 or more
compact fluorescents at a time, you can purchase them on-line
for as little as $6 per bulb. (Check out the links at the
bottom of this page for on-line shopping sites.)
The upside to compact fluorescent bulbs' costs is that
they last a very long time. The rated lifetime of most compact
fluorescent bulbs is 10,000 hours. I twice tried to check
this figure by turning on a light in my office and leaving
it on. Both times that I tried this, however, I changed
offices before the light burnt out. In contrast to the long
lifetimes of compact fluorescent bulbs, incandescent bulbs
are rated to last from 800 to 1,000 hours. It would take
10 or more incandescent bulbs to match the life of one compact
fluorescent.
Now, let's add both types of bulbs' initial costs to their
yearly energy costs and compare apples to apples. If you
use a 60 watt incandescent light for a bit less than 3 hours
each day, or 1,000 hours each year, and your local electric
rate is 10 cents per kilowatt-hour, then the light is costing
you $6 per year in electricity. Add 50 cents for a new bulb
each year, and you have a total cost of $6.50 every year.
A single compact fluorescent would initially cost you $10.00
for the bulb, but would only cost you $1.50 in electricity
each year.
One might be tempted to say that 10 years of lighting
will cost $65.00 for each 60 watt incandescent bulb and
just $25.00 for each 15 watt equivalent compact fluorescent
bulb, but that would ignore the notion of discounting future
costs. To help you with the discounting calculation, we
have created the little calculator below. All you need to
do is replace the numbers that appear in the boxes with
your own local information. For instance, if you live in
the service territory of a utility that charges 13 cents
per kilowatt-hour, you should replace the "10" in the first
box with "13". If you have a lighting fixture that stays
on for 6 hours each day and has five 60 watt incandescent
bulbs, then you need to replace the "3" that is in the second
box with "6", the "60" in the first box of the second table
with "300", and the "15" in the second box of the second
table with "75".
When you have filled in the information to your satisfaction,
click on the "Compute" button below the tables.
|
