Mr. Electricity is your guide to saving energy in your home.
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If you like this site, you might also like some of my
other sites:
Battery
Guide
Which battery is best? We cover
rechargeable and alkaline batteries to show you what's hot,
what's not, and the best way to charge them. (visit
now)
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The
Military Budget as Cookies
This excellent animation from TrueMajority shows in
graphic detail (using Oreo cookies) how ridiculously, large
the military budget is, and how we could solve many domestic
problems with a modest 12% cut. A must-see. (watch
it now)
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 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. On this page I'll give you the
lowdown on CFL's in great detail.
I first recommended CFL's on this
site way back in the 1990's, when they
were rare. It was kind of neat back
then to let people in on a big secret.
It's not such a secret any more, but I'm
glad people are saving energy with
CFL's.
To understand why CFL's are a big
deal, we first need to see why regular
lightbulbs are so lame. Environmental
Defense has the best explanation of
what's wrong with regular light bulbs:
"Though
we call them light bulbs, traditional
incandescent bulbs are actually
small heaters that give off a little
bit of light--something you know if
you've ever touched a bulb that's been
on for a while. These bulbs were
technological wonders when they were
patented in 1880, but today they are
inefficient dinosaurs. They waste
energy and money, and they are
responsible for millions of tons of
global warming pollution."
Compact fluorescent light bulbs
(CFL's) are the opposite -- they create
mostly light and give off only a little
bit of heat. They use 70% less
electricity than regular light bulbs,
since most of the electric you put into
them is used to make light, not heat.
Here's are the benefits of
CFL's:
- Use 70% less energy than regular
light bulbs.
- Last about 10 times as long as
regular light bulbs.
- Produce similar light as regular
light bulbs (nothing like old-style
fluorescents).
- Cost as little as $1.50.
- Don't generate ridiculous amounts
of heat (which you would have to pay to
remove with AC).
And here are the downsides:
- Most of them can't be used with
dimmer switches. (Some can; check the
package.)
- Cheap ones burn out really quickly.
Buy name brands and/or bulbs with a
warranty.
- They start dim and take a minute or
two to reach full brightness.
- They contain a tiny amount of
mercury, which would be an issue
if you break a bulb and
you're careless about how you
cleaned up a broken bulb.
CFL's are such a big deal that
Australia
is making them mandatory.
They're doing this to save energy, because
saving energy reduces pollution.
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:
And that's just the electricity
savings. Since a good CFL lasts 10
times longer than an old-style bulb,
that's a lot fewer bulbs to buy. This is
especially important for large commercial
applications, where the cost of labor to
constantly replace old-style bulbs can be
significant.
But there's yet more savings.
Since CFL's run cooler than old-style
bulbs, you'll spend less money to cool
your home or office. (But don't think that
this means you should use regular lights
in winter; sure they create heat, but they
do so inefficiently. When you
need to add heat to your home,
light bulbs are the most wasteful way to
do it. Short answer, CFL's are best no
matter what the season.)
To figure your electricity savings
manually use this formula:
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Watts
x
Hours Used
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x
Cost per kilowatt-hour
=
Total Cost
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1000
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For example, let's say you replace ten
60-watt bulbs with ten 15-watt CFL bulbs.
That saves you 45 watts per bulb, or 450
watts for all ten. Let's say all your
lights were on for six hours a day, five
days a week. That's thirty hours a week,
or about 1500 hours a year. So your 450
watts savings times 1500 hours a year =
675,00 watt-hours. Divide by 1000 and you
have 675 kilowatt-hours (kWh). If you're
paying 15¢ per kilowatt-hour, then
you'll save $101.25 a year.
If you don't like my calculator there's
also a
calculator at EnergyStar.gov.
How to buy
CFL's
When you buy CFL bulbs the package
will be labeled to show you how many watts
it's equivalent to. For example, a
15-watt CFL bulb package will say
something like "60 watt equivalent". They
have to say that otherwise people would
look at the package and think, "15 watts?
That's not nearly enough light!" But it
is, because a 15-watt CFL bulb puts out as
much light as a standard 60-watt bulb.
Although CFL's generally last for years
longer than regular bulbs, the cheap
kind can burn out quickly. I therefore
recommend buying either name-brand
CFL's, or at least ones that come with
a 5+ year warranty.
If you're in a super-cold environment,
note that most CFL's run dim in very cold
temperatures, and most won't run at all
below 20°F. (Paralite
makes some they claim will work down to
minus 20°F.) If you're using
them outside as floodlights, then make
sure you get the kind that are labeled for
cold-weather use. One reader notes that he
put a $10 bug light sleeve around the
light which acted like insulation, and
kept the light just warm enough that it
would work.
The great
mercury scare
I can't really broach this subject
without mentioning where the scare
warnings have been coming from:
Republicans who want to fight
conservation. The reason this is
significant is that Republicans have
fought against pollution controls and
championed the "rights" of polluting
companies at nearly every turn for years.
So how is it that they're suddenly so
concerned with the mercury in CFL's?
Is it because they suddenly want less
pollution, after decades of acting the
opposite way? No, they oppose CFL's
because CFL's save energy, and because
environmentalists support them. That's all
the reason right-wingers need to oppose
them. They simply need some excuse, and
mercury happened to be convenient. Really,
we're supposed to believe that after years
of blocking every effort to reduce
pollution, the Republicans are suddenly
eager to save Americans from toxic
substances? Please!
Think I'm exaggerating? Here's the
proof. Rep. Ted Poe (R-TX) took
the floor of the House to blast CFL
lightbulbs and opened up with this
flabbergasting statement:
"Congress
passed an energy bill which should have
been called the 'Anti-America
NON-Energy' Bill because it
punishes Americans for using energy,
rather than finding new sources of
affordable energy."
There you have it. Any attempt
to reduce our energy use isn't just
unnecessary, it's supposedly
anti-American! And reducing energy
use is tantamount to punishment.
Punishment! Since Poe is an unabashed
enemy of conservation, is it any
freaking wonder that he opposes
energy-saving light bulbs?! Is it any
surprise that he will bring up any
possible defect he can find in CFL's in
order to further his anti-conservation
agenda?
It gets richer. In Poe's mind, all we
need to do is magically find some new
sources of affordable energy. And what do
you think he has in mind? Why, drilling
the Artic National Wildlife Refuge and
America's beaches for oil, for starters,
something Republicans have been eager to
do for years.
Anyway, when Poe has made his
anti-environmental agenda so clear and
plain, are we really supposed to take him
seriously when he starts frothing about
the environmental calamity posed by
mercury in CFL bulbs? Not.
With that necessary context out of the
way, let's look at the actual risk. First
of all, there is no risk as long as the
bulb doesn't break. You'd think that
would be obvious, but some of the hysteria
surrounding CFL's is coming from pages
that say that just having CFL's installed
in your home is "killing you slowly" --
which is absolutely nonsense.
Another idea being bandied about is
that the use of CFL's is resulting in a
lot more mercury getting into the
environment, in general. Not true,
because power plants put out tons of
mercury. They put out more to power
the bulb, than is contained in the bulb.
(Ohio
EPA)
And if you're using
old-style, energy-wasting bulbs, then that
means even more mercury being put into the
air. So using CFL's dramatically reduces
mercury emissions at the power plant. And
by the way, to keep mercury out of the
landfill, every single Home
Depot and Ikea take unbroken CFL's to
recycle them.
Next, let's put the amount of mercury
in perspective:
If a bulb does break, you just take
some
simple steps to minimize your exposure
when cleaning it up. You certainly
don't have to call in a hazmat team.
One woman got bad advice that she needed
to do just that, and the anti-CFL folks
have been having a field day with that
one, not admitting that the advice this
person received about employing a hazmat
team was wrong.
Let's also remember that tubular
fluorescents have been used in commercial
and office buildings for decades.
This is not a new technology at all. Why
have the Republicans been silent about the
millions of fluorescent tubes that have
been in use over the last century? Good
question.
All that said, there should be a
warning on the package. Really,
anything that's a potential mercury hazard
should be labeled. I believe it's nothing
to worry about as long as you take the
easy recommended steps to clean up any
broken bulb, but those steps should be
included in the product. And I don't think
the mercury in the bulbs is a good reason
not to use them -- it's just not that big
a deal.
More on this:
Other
ways to save on lighting
energy
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
#6: 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
#7: 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 primary
lighting: Not yet ready for prime
time
LED's would be great for primary
lightning except for a few things:
- They're not nearly bright enough to
light up a whole room, unless you used
a bunch of them.
- Most models put out a cold, bluish
light, rather than the warm, yellowish
light of a regular bulb.
- They're crazy expensive.
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 200 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 $60 to
get the equivalent of a 14-watt bulb.
The problems with LED's may be solved
in a few years, but not yet. Yes, I know
Enlux
makes a 65-watt equivalent that produces
warm light. The problem with it, besides
its $90 (!) cost, is that it uses 22
watts, more than a CFL.
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.
Below are questions I've received
and answered about how saving electricity
on lighting.
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What do you think of
the LongLite
product that says it reduces lighting energy by
10%? --Feb.
2007
I think it's useless. Why would you cut
your energy use by only 10% when you can get
compact fluorescents and cut it by 75%? "Oh, but
this product also makes the bulbs last three
times as long." Big deal, compact fluorescents
last ten times as long.
Go with compact fluorescents.
Our plant has a
combination of high pressure sodiun and mecury
halide light fixtures. Currently they are on 120V
circuits. Each fixture draws 4A on 120V, but can be
wired 277V and would draw 1.7A. I calculate that on
120V the fixture uses 120 x 4 = 480watts, and on
277V the fixture uses 277 x 1.7 = 471watts. This is
a 9 watt savings per fixture. We have 60 of these
fixtures in the plant, so 60 x 9 = 540 watt
savings. We run the plant one shift, 5 days a week,
so if I assume the lights are on 10 hours a day for
250 days a year, thats 2500 hours and we would save
540watts X 2500 hours = 1350000 watthours, or
1350kwh per year. Electrical cost here is about
$0.10 per kwh, so by my calculation we would only
save $135 per year. Is my calculation correct?
--Mark Jones,
Georgetown, KY, Jan. 2005
Yes, you got the math exactly right.
It's exactly this kind of calculation that I
hope to show my readers how to do.
I caution you though that the savings are so
small (<2%) that you might wind up not seeing
any savings at all. There could be a margin of
error for various reasons.
Are 34W fluorescent
tubes interchangeable with the 40W tubes? Ditto for
a T8 32W tube with a T12 40W tube when used with an
electronic ballast?
--Peter Yee,
Oakland, CA, Jan. 2005
Usually it's fine to swap a 40W tube
with a 34W tube, but some ballasts can overheat
with a 34W tube installed. Check the ballast to
see if it says it's rated for 34W tubes, and if
it doesn't then check with the manufacturer of
the ballast. In a worst-case scenario you could
replace the existing ballast with one you buy
specifically because it's rated for 34W.
32W T8's are another matter -- they require
ballasts made just for them.
The main risk of using a mismatched
tube/ballast is that the life of either or both
can be shortened. There's also the possibility
that the ballast could catch fire.
Since I get a fair number of questions about
fluorescent lights here are some other
resources:
We have fluorescent
lights in our building hallways that use two tubes.
A neighbor insists that if we just use one of the
bulbs we would save electricity. However, I once
read that the fixture will continue to draw the
same amount of electricity regardless of whether
you are just using one bulb. Who is right?
--Liam, NYC,
Jan. 2005
I'm amazed at all the bizarre
misconceptions people come up with. It seems
like there's no end to it. Examples include:
- The idea that it takes more energy to
turn on lights or computers than to keep them
running.
- The idea that it takes more energy to
turn on the AC when you get home from work
rather than to run it all day.
- The idea that a lamp uses energy even
when it's turned off.
- The idea that a 60-watt bulb uses more
energy than a 100-watt bulb.
- And now this: Someone who thinks that one
light bulb uses the same amount of energy as
two light bulbs.
Look through this site and you will see that
the number of times I've confirmed any crazy
idea like this is zero. To answer your question
specifically, no, one bulb does not use as much
energy as two. One bulb uses one bulb's worth of
energy, and two bulbs uses two bulbs' worth of
energy.
In 2000 I changed all
of my light bulbs to CFL. It cost me about $400 for
my house. Within 2 years I was replacing most of
them. After 4 years, I reviewed all of my electric
bills and found out there was no noticeable
difference in how much electricity I used. I
started switching back to incadescent bulbs a year
ago and now that is all I have. No significant
difference in my electricity bill or in kWh used,
as I expected. I have consistently used between 600
and 700 kwh per month for the past 10 years. The
only things that have made a difference in my power
bill is getting rid of my water bed and buying a
new refrigerator.
What gives? I thought
the CFL were supposed to make a significant
difference in power used. I don't get it. Is it
possible that some of the CFL bulbs I bought were
crap or not what the manufacturers promised? I
really would like to understand this.
--Marvin Snapp,
Mill Valley, CA, Jan. 2005
(1) CFL's really do use about 75% less
energy than regular light bulbs. I think you
really saved energy but didn't realize it. More
on this in a minute.
(2) You either have a bunch of lights
or you paid a lot for your CFL bulbs. My
home improvement store has CFL bulbs for $2.50
each. You could outfit a whole house for only
$40, not $400. Yes, CFL's were more expensive
five years ago, but they weren't that
much more expensive. Anyone wanting to outfit
their home in CFL's today isn't going to spend
$400.
(3) You said you started replacing your bulbs
after two years, but didn't say whether that was
because they burned out or you didn't like the
quality of the light. If it's the former, then
realize that many CFL's have a multi-year
warranty. I definitely recommend getting CFL
bulbs with a warranty. I've had good success
with my CFL's. I can't remember the last time I
bought a bulb, but it was many years ago.
It's easy to verify that your CFL bulbs use
less energy than regular bulbs. Put the bulb in
a lamp and then plug the lamp into a watt-hour
meter. Then try an incandescent bulb. You'll
see that the CFL uses 75% less energy. I doubt
that a CFL could use as much energy as a regular
bulb even if it were low quality or damaged.
How much difference did you expect to see in
your bill? From our How
much your stuff uses page we see that
lighting accounts for 9.2% of the typical bill.
If you were saving 75% of that than you should
have saved 9.2% x 75% = 6.9%. If you had been
using 700 kWh before, then you'd be expected to
save about 6.9% of that, or 48 kWh, so that
you'd use a total of 652 kWh. That's right in
line with your reported results: between 600 and
700 kWh. I think you were really saving energy
and just didn't realize it.
Of course, your own usage affects the outcome
(you could be using your lights more or less
than 9.2% of your total energy use), and of
course your energy use in general varies from
month to month. For these reasons looking at the
total kWh reported on your bill doesn't really
help you see how much your CFL lights were
saving you.
Your web site is
fantastic and by utilizing most of your tips I have
succeeded in reducing my daily average kWh usage
from 45 down to 17! I am not exaggerating, I truly
reduced my consumption by 60%. My question to you
is this: I have six PAR20, 50-watt Halogen bulbs,
four of which are on a dimmer, that I would like to
change to CFL. Is there a replacement bulb out
there for this application?
--François
Cornwall, Ontario, Canada, Dec. 2004
I can easily believe that you got down
to 17 kWh/day because I use only 5 kWh/day
myself. Still, it's impressive that you reduced
your usage by 62.2%. I don't know how much
you're paying for electricity, but at
10¢/kWh you'd be saving over $1000/year, in
U.S. currency.
Service
Lighting has dimmable CFL's in the PAR
style. They might be a little too long for your
tastes but that's the nature of CFL's.
Incidentally, Service Lighting also has good
bulb size charts for both fluorescent
and incandescent
lights.
I recently bought a 36"
fluorescent light that is ready to plug in made by
GE. The note said that the replacement bulb should
be of specific type and should be 25 watts. I did
not like the color of the light but I could not
find any 36" lights that were 25 watts so I
replaced it with a 30 watt bulb. It appears to work
fine, but is there anything wrong by exceeding 5
watts for the bulb in my case?
-- Budi
Widjaja, Mississauga, Dec. 2004
If the manufacturer says you shouldn't
exceed 25 watts, then I wouldn't exceed 25
watts. For a more definitive answer I suggest
contacting the manufacturer, since they're the
ones who came up with the 25-watt limit.
The lights in my dorm
room are fluorescent, I believe 16" tubes. I want
to remove these bulbs and find some adapter that
allows me to plug in something else. I know there
is a step up box in the fixture and I probably will
not be able to remove
that. -- Chris
Weed, Wisconsin, Dec. 2004
Sorry, I generally only answer
questions about saving electricity. I
don't know about any kind of non-fluorescent
light you could put in a fluorescent light
fixture, but then again I'm not the right person
to ask because this isn't my specialty. In any
event, it's rather impossible for me to suggest
alternatives since I don't know why you're
dissatisfied with your lights in the first
place, since you didn't say. If it's buzzing
then you need a new ballast (fixture). If you
don't like the kind of light it puts out, you
can simply get different style tubes.
If a light fixture
doesn't say what the watt limit is, how many watts
can I use safely? We have a two-bulb light kitchen
ceiling fixture. My husband put in two 100-watt
bulbs and I am worried about having a
fire. -- Linda
Davis, Rochester, NY, Dec. 2004
First of all, smack your husband upside
the head and tell him it's from me.
Next, if you simply use compact fluorescent
bulbs then you won't have to worry about going
over the limit, no matter what it is, since
CFL's use such a small amount of energy. A
25-watt CFL puts out as much light as a 100-watt
incandescent light. Plus, you'll pay 75% less to
light your kitchen.
Third, why the heck do you need so much light
in the kitchen? 200 watts?! Is the kitchen
painted black? Or is it more than 300 square
feet?
Next, if you really need that much light in
your kitchen, you probably want a better system
than putting it all in one spot in the ceiling.
That's gonna be harsh. Consider using lamps, or
installing a fluorescent panel, or using some
other kind of distributed lighting.
Finally, if you (or your husband) are dead
set on using incandescent bulbs instead of CFL's
and the fixture is unrated, then I wouldn't go
over 60 watts each, since that's the lowest I've
seen a socket rated for. Of course, you could
always replace the socket with a 100-watt
socket.
We have 36 Metal Halide
lights that we are going to hang in an indoor horse
riding arena. If I wire these at 240v they draw 1.3
amps each. If I wire these at 277v they draw 1.1
amps each. This is just 0.2 amps difference. Based
on your formula would that be 0.2 amps x 120 volts
= 24watts, x 36 lights = 864watt? Is it worth
spending approximately $1300 additional dollars to
buy and install step-up transformer to jump the
voltage from 240v to 277v and how long would it
take me to recoup that money?
-- Wayne
Lawhorn, Richmond, VA, Nov. 2004
There are two mistakes here. As it says
on our how they charge you
page, the electric company charges you
according to how many kilowatt-hours you use,
not how many amps you use, so you shouldn't be
comparing the difference in amps. Second, when
you multiplied amps times volts you used 120
volts for some reason rather than the voltage
your lights actually draw.
To figure this properly we have:
- 1.3 amps x 240 volts = 312 watts for the
first light, and
- 1.1 amps x 277 volts = 305 watts for the
second light
That's a difference of 7 watts per bulb.
Since you have 36 of them that's a difference of
252 watts for the whole set (0.252
kilowatts).
You didn't mention how much you're paying for
electricity, but let's assume it's $0.15. At
that rate you're paying $0.15 x 0.252 =
3.8¢ extra for every hour that you run the
set. At that rate it would take over 34,000
hours for the 277 lights to pay for
themselves.
You will save a lot more money by using
fluorescent lighting instead.
How much electricity
does a night light take?
-- Anonymous, Nov.
2004
Standard night lights use around 5
watts. LED models use about 1 watt. And the
"LimeLight" electroluminescent light uses only
0.03 watts!
Remember that the wattage is listed directly
on any device you can plug into the wall.
I am a business student
at the University of Utah. For my final
project in a statistics class I need to determine
how much energy a light bulb uses right when it
turns vs. after it has been running for 5
seconds. It is that initial fluctuation that
I cannot figure out how to measure. I was
wondering if you know how, or if you have a device
that could measure that very slight
fluctuation.
-- Michael Ford, Utah,
Nov. 2004
You didn't mention what your point is
in trying to measure the surge (i.e., what
you're trying to prove), but I'm certain you (or
your instructor) is barking up the wrong tree.
As I've said many times, for all practical
purposes the surge is so tiny as to be
irrelevant. You would need special, expensive
scientific equipment that you don't have access
to and don't know how to use in order to measure
the first few milliseconds or microseconds of
electrical use of a light bulb. If the energy
used were significant then you wouldn't need the
equivalent of an electricity microscope to find
it.
You can prove this by using a watt-meter to
measure the electricity used for one second,
then multiplying by 3600 seconds to get one
hour's worth of electrical use. Then use the
meter to measure the electricity used for one
hour, and compare the two figures. You won't see
a difference. Any difference you might see is
the result of your not turning the meter off at
precisely one second after turning it on.
I have a light bulb
socket that's labeled "60 watts max". I screwed an
adapter into it so now there's two sockets. I want
to put a compact fluorescent bulb in each socket,
but I want to make sure I don't go over the 60-watt
limit. I got some bulbs from IKEA that say they are
11 watts but that they are approximately 60 watts
light output. Is it okay to plug two 11-watt
energy-saving bulbs into it, even though the "light
output" is 60 watts per bulb? In other words,
am I using 22 watts or 120 watts total? Thank you
for your time! -- Christine Quigley,
May 2004
Good question. You're using 22 watts
total, so your lights will be fine. The package
is just telling you that each special 11-watt
bulb gives as much light as a standard 60-watt
bulb. If they didn't say that then no one would
buy them, because they'd say, "11 watts?! That's
not nearly enough light!"
In fact, though, I'd expect an 11-watt CFL
bulb to be equivalent to only a 40-watt standard
light bulb. It sounds like the light output
claim might be a little exaggerated. The general
rule of thumb is to multiply the CFL wattage by
four to compare it to a standard bulb. (e.g.,
15-watt CFL is comparable to a 60-watt standard
bulb, as far as how much light they put out)
Do dimmers on lighting
fixtures reduce wattage and save money?
-- Eldon McElhiney, Feb. 2003
Yes, they do. But compact fluorescent
(CF) light bulbs save even more money. A 25-watt
CF bulb puts out as much light as a 100-watt
regular bulb. If you used a dimmer on a 100-watt
bulb to take it down to 25 watts, there wouldn't
be much light.
Most CF's can't be used with dimmer switches.
If your fixture is controlled by a dimmer, then
either read the package on the CF bulb to find
one that works with a dimmer switch, or replace
your dimmer switch with a regular switch.
Note that old dimmers were rheostats
which did NOT save electricity -- and they
generated dangerous heat, to boot. I don't have
any idea when they switched from rheostats to
the modern solid state variety, but here's how
you can see if yours is old or new:
- Turn off any device that could automatically
turn itself on (like your AC and
refrigerator).
- Turn on your light at full brightness.
- Look at your electric meter and write down
how long it takes to make one revolution.
- Turn the dimmer down to about 25%
brightness.
- Check your meter again.
If it took longer for the meter to spin, then
you have a modern dimmer which is saving energy.
If the meter speed remained the same, then you
have an old-style dimmer and turning it down
doesn't save energy. In that case, replace your
dimmer with a modern one. You can have an
electrician do this for about $40 if you're not
comfortable doing it yourself.
By the way, even though modern dimmer
switches save energy when you dim the lights,
the lights dim more than the energy is
decreased. That means if you make it half as
bright, you don't save quite half as much
energy. But this is really trivia, and you don't
need to worry about it.
If I turn my dimmer to
the lowest setting/level (where there's no visible
light) is it the same as turning it off? Is the
switch turned off in both cases and hence not using
any electricity? I find it easier just to turn down
the dimmer but am not sure if it's still using
electricity when at its lowest level.
-- Anita Low, Dec 2003
As long as your dimmer isn't an ancient
rheostat (see below) then turning it down so far
that you can't see any light is the same as
turning it off -- no energy use. (Well, there
might be some energy use, but it will be
so tiny as to be negligible. If you want to find
out for sure you can turn off and unplug
everything in your home except the dimmer and
see if your electric meter is still moving. But
I wouldn't worry about it.)
I read on your site
about using LED Christmas lights. What about using
LED lights for primary (room) lighting? Does such a
thing exist? -- Anonymous, Nov 2003
LED's would be great for primary
lightning except for a a couple of things:
First, they're not nearly bright enough to light
up a whole room, unless you used a bunch of
them, which would be prohibitively expensive.
(Maybe $100 for enough LED's to replace a
100-watt bulb.) Also, the light they produce is
brilliant white, like old-style fluorecents,
which is kind of harsh. These problems may be
solved in a few years, but not yet. In the
meantime, LED's are great for applications like
flashlights, bicycle lights, and holiday lights.
We converted our house
to energy efficient appliances and use all compact
fluorescent lights, together bringing down my
monthly usage from a budget of $98 to a high of $52
in August and a low of only $17 in June. We are
elated! However these bulbs do not work well to
light up the outside when it gets below zero. We
burnt out some trying. At our local Menard's they
sell a outdoor Regency fluorescent light and
fixture that has a solid state on switch allowing
it to operate in colder temperatures. However the
only bulb option they offer is the old blue look of
death. Do you know of any manufactures of solid
state outdoor fluorescent fixtures that uses a true
white bulb? -- Paul & Julieta
Werner, April 2004
First, congratulations on your savings!
See, readers, these tips really can save
you money. Okay, onto your question. Most CF's
won't work below about 20°F. Paralite
makes some they claim will work in temperatures
as low as -20°F (that's minus 20
degrees), but I don't know what the output looks
like. If it's not suitable you may have no other
choice but to use standard floodlights for your
outdoor fixtures in the winter.
I was wondering, how
much will I actually save if I switch from four
T-12 fluorescent lights (two 34w & two 40w
bulbs) to four T-8 bulbs, run about 60 hrs/week at
$.08/kWh. A lot of lighting sales people have
different answers, one told me I would save approx.
$36 per year with a high power factor electronic
ballast, because of lower power consumption, and
heat savings factor on A/C. Please set me
straight! -- The Pattersons, June
2003
The Pattersons are talking about those
long, fluorescent tube lights that are standard
in offices and schools. The short story is that
T-12 is old-style and uses the most electricity.
Modern replacements are T-8's, and new
energy-efficient T-12's. Here's a table to
summarize:
|
|
Watts
|
Brightness
|
Heat
|
Ballast
|
|
T-12
|
40
|
Dimmer
|
Warmer
|
Electronic or Magnetic
|
|
T-12, energy efficient
|
34
|
|
T-8
|
32
|
Brighter
|
Cooler
|
Electronic Only
|
In simple terms, the ballast is the socket
that you screw the lights into. Old-style
magnetic ballasts are known to hum and produce
the annoying flicker that can give you
"fluorescent headache". Modern ballasts are
electronic, quiet, and produce no noticeable
flicker.
T-8's are definitely the best choice, because
they use the least electricity, produce the most
light, generate the least heat, and will
definitely be used with a flicker- and hum-free
electronic ballast. They also contain less toxic
chemicals, and you can also put up to four T-8's
into a single ballast. They only reason they
still make T-12's is because of all the old
magnetic ballasts already out there that won't
take a T-8.
So to answer the Pattersons' question: If
they're using 148 watts now (40+40+34+34) for 60
hours a week that's 8800 watts a week, or 462kWh
a year, which at $0.08/kWh comes to $37.
Switching to four T-8's would mean 128 watts
(4 x 32), and at 60 hours a week that's 7680
watts a week, or 399 kWh a year, which at
$0.08/kWh comes to $32, a $5 savings, which
wouldn't cover the cost of the new lights and
ballasts. Still, it could be worth switching
just to have brighter light, and to get it
without the annoying flicker.
And what about the savings from decreased
cooling costs from running lights that don't put
out as much heat? While those savings are real,
they're notoriously hard to calculate,
especially because they vary from building to
building depending on insulation, ambient
temperature, climate -- and of course it even
varies from season to season. A commercial
lighting specialist might have access to such
estimates but that's definitely out of my realm
of specialty.
By the way, the tubes get their names from
the number of eighths of an inch in diameter
they have. T-12 is (12/8) or 1.5", while T-8 is
(8/8) or 1".
Our office is having a
disagreement regarding this question. Some say that
when you turn on a fluorescent light it takes more
electricity to charge it up and we would be better
off keeping the lighting on all day.
-- Heather Burton, Houston
TX, 10-00
Your coworkers are wrong; lights don't
require extra measurable amount electricity to
start up, whether they're fluorescent or normal.
You can stand there and flip the light on and
off repeatedly, and it won't make any difference
in your electric bill.
Think about it: Even IF a fluorescent used
ten times as much energy for the first
full second it was on, then basically it's using
an extra ten seconds of electricity. So as long
as you were turning the light off for at least
ten seconds it would pay to turn it off. If you
start thinking about it this way then it's easy
to see why this myth is wrong.
But remember, in reality, flipping the light
on doesn't burn a measurable amount of extra
electricity. And that's true of regular lights
as well as fluorescents. So it always pays to
turn them off. You don't use extra electricity
when you turn the lights on, so always turn them
off when you're not using them.
Here's another way you could debunk the myth:
Go outside and look at the electric meter as
someone flips on a fluorescent light. If the
light needed a surge of electricity, you'd see
the meter spinning blindingly fast for a few
seconds, and then slow down again. But that
doesn't happen, because lights don't need extra
electricity to start up.
By the way, campers have used battery-powered
fluorescent lanterns for years. They wouldn't
work if fluorescents needed extra power to start
up, because if they did then the batteries would
be drained right away.
Okay,
the fluorescent might not require extra electricity
to start up, but every time you turn it on you wear
it out a little bit, so that means you should
always keep the lights on, right?
-- various
readers
No. Fluorescents do get worn out by
power cycling but the effect is so small it's
negligible. So one seems to believe me without
seeing an equation, so let's look at the math.
Bulb manufacturers typically test their
lights for three-hour periods. (Panasonic
tests for 2.5 hours on, 0.5 hour off.) For a
10,000-hour CFL, that's 10,000 / 3 = 3333
starts. If the bulb costs $2 then each start
costs 0.06¢. That's not six cents, that's
six-hundredths of a cent.
Okay, so let's say you're going to leave the
room for 16 minutes, and you're agonizing over
whether you should turn the lights off or not.
Let's also say you have two 15-watt CFL bulbs.
If you turn the lights off then you'll save 16
minute's worth of electricity, which is 30 watts
x 16/60 hrs / 1000 wh/kWh x 10¢/kWh =
0.08¢. When you turn them back on you'll
use up 0.12¢ of the bulbs' life (0.06¢
for each of two bulbs), for a net cost of
0.04¢. So yes, you're on the losing end by
turning off the light instead of keeping it on,
but what does this mean in practical terms?
Let's say that four times a day you have the
opportunity to turn the lights off when you
leave the room for 16 minutes, and you do so.
Over a year that costs you 4 times/day x 365
days/year x 0.04¢ = 58¢/year. Now, if
you want to obsess over 58¢/year, be my
guest.
Consider something else: Every time you leave
the lights on to "save" money and you actually
wind up leaving for more than 24 minutes, you'll
lose money because your electrical costs will
outweigh the savings of making the bulb last
longer. That will eat into your big $0.58/year
savings -- maybe even reversing it.
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