 How
to save electricity on
lighting
Use compact
fluorescent light bulbs
(CFL's).
If you know only a little about
CFL's, you've probably heard that they
save a little energy but they contain a
lot of toxic mercury. But the truth
is, they save a whopping amount of
energy, and the mercury scare is way
overblown.
Let's start out by looking at the
savings you get with CFL's. Right off
the bat, you save 70% on energy as soon as
you screw them in. Here's a calculator to
demonstrate:
But there are still more savings to
be had. Brand-new CFL's last 10 times
longer than old-style bulbs, and they
generate a lot less heat -- which means
lower cooling bills.
I have a separate
page which covers CFL's in detail,
including pro's, cons, how to shop for
them, and the real story behind the
mercury warnings.
Install a
skylight.
Using natural lighting saves a
bunch of energy and produces a much
nicer environment besides. Modern
skylights are available which let in
only the light and not the heat.
For outside
lighting, install a motion sensor that
turns the lights on automatically when
somebody walks up, and turns the lights
off automatically after 1-5
minutes.
Security light fixtures start
at $25 at home improvement stores like
Home Depot.
Exercise:
You buy a security light for $20. The
light used to be on all night, for 12
hours each night. Now it's on for about
an hour a night. You're using two
75-watt bulbs in the fixture. How long
does it take for the security light to
pay for itself? (assume electricity
costs 11¢/kWh) (see
answer)
- Old
way: 2 bulbs x 75W x 12 hrs/day
x 30.5 days/mo. ÷ 1000 w/kW x
$0.11/kWh = $6.04/mo.
- New
way: 2 bulbs x 75W x 1 hr/day x
30.5 days/mo. ÷ 1000 w/kWh x
$0.11/kWh = $0.50/mo.
- Savings
per month: $6.04 - $0.50 =
$5.54
- Payback
time: $20 / $5.54 = 3.6 months
Install
motion-sensing switches to automatically
turn lights on and off throughout the
house.
You can buy motion-sensing
wall switches for as little as $10 at a
home improvement store.
.
For any light
that you want to be on all night (e.g.,
stairways), replace the bulbs with the
lowest wattage bulbs you're comfortable
with.
Replacing 75-watt bulbs with
15-watt bulbs reduces energy usage by
80%. Replacing them with CFL's or LED
lights saves even more.
Exercise:
How much do you save in a year by
replacing a 75-watt bulb with a 5-watt
bulb, for a light that's on 24/7? Use
11¢/kWh for the cost.
(see
answer)
- Old
way: 75W x 24 hrs/day x 30.5
days/mo. ÷ 1000 w/kW x
$0.11/kWh = $6.04/mo.
- New
way: 5W x 24 hrs/day x 30.5
days/mo. ÷ 1000 w/kWh x
$0.11/kWh = $0.40/mo.
- Savings
per month: $6.04 - $0.40 = $5.64
(93%!)
For lights
that you want on all night which are in
areas that get some sunlight, buy a
screw-in light sensor.
They'll turn off automatically in the
morning and then turn on automatically at
night. My local home improvement stores
sells these for $4.50 ($8.50 for an
outdoor version). You just screw the
special socket into the existing light
socket, then screw the light bulb into the
special socket.
Exercise
#8: How long does it take for one
of these $4.50 devices (indoor version)
to pay for itself, assuming you were
using a 60-watt bulb, paying
11¢/kWh for electricity, and
saving 12 hours per day of light use?
(see
answer)
- Old
way: 60W x 24 hrs/day x 30.5
days/mo. ÷ 1000 w/kW x
$0.11/kWh = $4.83/mo.
- New
way: 60W x 12 hrs/day x 30.5
days/mo. ÷ 1000 w/kWh x
$0.11/kWh = $2.42/mo.
- Monthly
savings: $4.83 - 2.42 =
$2.41/mo.
- Payback
time: $4.50 / 2.41 = 1.9 months
You can also make lamps or other
devices go off during the day and turn on
at night by using a plug-in light sensor
($6). You plug the appliance into the
sensor, and then plug the sensor into the
wall. If you're handy with electrical
wiring, you can mount a light sensor to a
wall (like you'd mount a light switch or
electrical outlet). Wire-in sensors are
around $10.
Turn off
lights when you're not using them, even
for just a few minutes.
The idea that lights use extra
electricity to start up is a myth.
You'll save electricity every
time you turn the lights off, no
matter how short the OFF duration, and
whether they're regular lights or
fluorescents.
You might have heard that you wear
out your lights quicker by cycling them
off and on, but that effect is so small
it's not worth worrying about, and you
can safely turn your lights off every
time you leave the room, no matter how
short the duration. If you feel you
need to obsess over this (as evidenced
from all the email I get about the
subject) then see my answer below about
fluorescent cycling
costs.
Replace
fluorescent magnetic ballasts with
electronic ones.
For long-tube fluorescent
lighting (as opposed to screw-in
compact fluorescents), an old-style
magnetic ballast might use 100W to
power two 40W tubes, while an
electronic ballast might use only 60W.
Also, the electronic ballast eliminates
flicker and usually eliminates hum.
They also generate less heat, which
saves additional money on cooling.
Use LED
holiday lights.
LED Christmas lights use
80-90% less electricity than standard
holiday lights (which use 25 watts in a
typical 50-bulb strand). LED lights
also generate much less heat, so
they're less likely to catch your
Christmas tree on fire. Also, you can
put a few strands of white lights on
the ceiling and use it as mood
lighting.
LED holiday lights aren't quite as
bright as standard bulbs, and the light
they produce is brilliant white instead
of normal yellowish light, but that's
fine with us to get the 90% electricity
savings. (And blue, yellow, and red are
also available.) Another advantage is
that the LED's are virtually
indestructible -- they don't burn out
like normal bulbs (not for about ten
years, anyway), and they're not fragile
like normal holiday lights. I actually
unsuccessfully tried to crush one by
standing on it on a concrete surface. I
broke the decorative casing but was
unable to break the LED bulb itself --
it still shone when I plugged it back
in.
Inirgee
sells a nice variety of LED lights
in a variety of colors: 120V holiday
light strings, and 12V holiday light
strings to be powered from a battery.
Notably, most of the products carry a
lifetime warranty.
We have a separate page about
rewiring
Christmas lights to run off
batteries.
LED lights:
Not for primary lighting
LED's are great for holiday
lights, accent lighting, mood lighting,
and landscape lighting. But they
can't replace CFL's as primary lighting
yet for most people. That's because:
- Most models put out a cold,
bluish light, rather than the warm,
yellowish light of a regular
bulb.
- They send light in only one
direction, so bathing a room in
light is impossible.
- They're crazy expensive. We're
talking $120/bulb.
Environmentalists are excited about
these bulbs because they use even less
energy than CFL's, and without the
toxic mercury. But they're just not yet
ready for prime time. By 2011, maybe.
(Readers can feel free to write me in
2011 to remind me to update this page
by then if I forget.)
Here's how the various lighting
technologies stack up:
|
|
Incandescent
|
CFL
|
LED
|
|
Watts
|
60
|
15
|
7.5
|
|
Lumens
(brightness)
|
850
|
850
|
446
|
|
Toxic mercury
|
|
✓
|
|
|
Price
|
$0.40
|
$2.00
|
$120.00
|
Most online stores don't even bother
to tell you how bright their LED bulbs
are, in either lumens or incandescent
watt equivalents, because they probably
figured that if you knew how dim these
bulbs were there's no way you'd buy
them. An exception is C.
Crane, who is to be commended for
providing this info right up front.
Unfortunately, the biggest bulb in
their catalog is only 446 lumens.
Compare that to a traditional 60-watt
bulb (or a 15-watt CFL) which gives off
about 850 lumens of light. So you could
spend $120 to get the equivalent of a
30-watt bulb.
LED's are good for accent
lighting, night lights, and decorative
lighting, just not primary
lighting. I use LED Christmas
lights as mood lighting when I don't
need a whole lot of light. I hung a
couple of strands from hooks aroundthe
perimeter of my ceiling. Yeah, the note
that came with the lights said "This
seasonal use product is not intended
for permanent installation or use," but
I guess I live on the wild side.
Commercial users might like LED
bulbs because they last nearly forever
-- 50,000 hours of use. In an
installation with lots of bulbs and
where they're hard to reach and the
labor cost of replacing them is high,
LED's might be a good alternative.
Commercial users will also want to
check out the products at Residential
Landscape Lighting.
The Simple Dollar has a great
review of LED light bulbs.
Related pages:
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