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Questions
about computer electrical use from
readers
This page is the companion to my article,
"How much
electricity do computers use?"
That page is more likely what you're looking
for.
What do you think about
the idea of petitioning Google to use a black
background to save energy, or encouraging people to
use Blackle,
a black-background version of Google?
-- January
2008
It won't save squat. Instead we
should be focusing on things that really matter,
like heating,
cooling, and
lighting use -- or
even just sleeping or
turning off our computers when we're not
using them.
For those who haven't heard about the black
background thing, the idea is that it takes more
energy for a computer screen to show a white
background than a black background. But there
are three reasons that make this irrelevant:
- It's only true for obsolete CRT's, not
modern LCD's. CRT's are the huge, clunky
old-school monitors that are like TV's, which
are already obsolete. By contrast, LCD's are
what most people are using today, and a black
background makes no energy difference on an
LCD. An LCD uses the same amount of energy no
matter what the background color. I just
checked Best Buy, and they're only offering 2
different CRT's...and 41 LCD's! So for most
people, the background color makes no
difference at all. (And if you do have
an old CRT, the best way to save energy with
it isn't to use a black Google, it's to get
rid of it and replace it with an LCD, and
then sleep it when you're not using it.)
- Most people probably don't search
Google from its home page anyway. Modern
browsers and toolbars have a Google search
box built right into the browser window, so
you can search from any window without
actually visiting the Google home page. I
can't remember the last time I went to the
Google home page. It's probably been
years.
- Even for people with old CRT's who
actually go to the Google home page, the
savings is tiny. Even after all the
international press that Blackle has
received, they claimed to have saved only 425
kWh for the nearly one year they've been up.
To put that into perspective, the typical
American family uses 888 kWh hours in a
month. So in nearly a year, Blackle
has saved less than half of what a family
uses in a month. This is just not
significant.
Me, I use around 125 kWh/mo., saving 663 kWh
vs. the typical household, or 217 kWh on a
per-person basis. In two months, I alone
save about as much as Blackle's whole
international operation saves in nearly a
year.
We can save tons of energy if we
switch to CFL
lightbulbs and address our heating
and cooling use. Or
we can chase the things that don't really
matter, like using a black background for
Google, and save nearly nothing at all.
You advise people to
sleep their computers, but computers wear out
faster when they're cycled on/off repeatedly,
because the constant heating and cooling expands
and shrinks the parts. You should read Google's
report on hard
disk drive
failures (PDF)
which proves this.
No, this is wrong. As I said quite
clearly on the computers
page:
- You won't wear out your computer
prematurely by cycling it a few times a
day. Modern computers are just not that
fragile. Jonathan Koomey, a project scientist
at the Lawrence Berkeley National Laboratory,
agrees: "PCs are not hurt by turning them on
and off a few times a day."
(Wall
St.
Journal)
- Even if cycling computers reduced their
lifespan (which it doesn't), your computer
will still become obsolete and get replaced
way before you wore it out.
- Running something all the time (which is
what you're suggesting) certainly wears it
out faster. Do you think your washing machine
would last longer if you ran it 24/7? Your
computer has moving parts too (in the hard
drive), and it can't run forever.
As for the Google report, it says
absolutely nothing about temperature changes
from cycling a computer making it wear out
quicker. Google's report covered drives that
were on continuously. They didn't look at
power cycling at all. As for temperature, they
found that "[F]ailures do not increase
when the average temperature increases. In fact,
there's a clear trend shower that lower
temperatures are associated with higher failure
rates."
Google also found that the more a drive was
used, the more likely it was to fail. (p. 5)
That supports my point that running
your equipment is what wears it out.
You advise people to
sleep their computers when they're not using them,
but what about using a computer's idle time to help
with scientific research, like the projects listed
at Grid
Republic?
Any energy use has to be weighed
against the benefit we expect to get from
it. Personally, I don't feel the alleged
gains from distributed computing projects are
worth the energy it requires and the pollution
it creates. Take a look at the projects: One
involves searching for extraterrestrial life. Of
course it would be kind of ironic if we actually
found some aliens and our contact with them was
necessarily brief because climate change wiped
out life on our planet shortly after we found
them. But the real irony is all the projects
about studying climate change itself! Now, which
is the better way to deal with climate change:
Continue studying something that's already
been studied to death, or stop causing it in
the first place? I'll choose the latter.
What do you think of
Shutdown
Day, where people
are encouraged to keep their computers off for a
whole day? --
Feb. 2007
It's an interesting idea, but it
won't save much energy, nor is that even the
point. From the organizers' website: "The
purpose is to get people to think about how
their lives have changed with the increasing use
of the home computer, how society is changing
and whether or not any good things are being
lost because of this. It is obvious that
computers are an extremely important and vital
part of society these days."
For energy savings, I prefer that we save
energy every day, not just one day a
year. Shutting your computer off for one day
saves only a piddling 1/365th of its use
annually. (0.3%) As I always say, most
people will save lots more energy by focusing on
their heating,
cooling, and
lighting use rather
than their computers. And with you computer,
setting it to sleep after X minutes of idle time
and swapping your old CRT monitor for an LCD one
will drastically cut how much energy your
computer system uses -- way more than you'd get
by turning your system off for just one day.
And of course, if you participate in Shutdown
Day and then watch TV or drive a car instead,
you're just trading one form of energy use for
another.
All that said, if Shutdown Day appeals to you
then by all means participate. Just don't fool
yourself into thinking that you'll be saving
lots of energy by doing so.
What do you think about
the push for more
energy-efficient
computers?
-- Dec.
2006
It's promising, for sure, but a year
later, what happened to that effort? If a
reader has heard any more about the effort to
make super-efficient PC's, I'd appreciate
hearing about it.
The article doesn't put the numbers into a
per-unit perspective, but they're significant:
They're talking about saving a whopping 45
watts. That's about a one-third savings. Also
note that just recently the EPA started granting
the Energy
Star label to energy-efficient computers,
though those standards are not nearly as strict
as the ones proposed by the article you
mentioned.
And as always, I remind readers that you'll
still save more energy by turning your old
product off when you're not using it than you
will by buying a new efficient model. Not
running an unused device is still way more
important than how efficient that device is.
The fact that you are
using a computer and wasting energy promoting your
ideas indicates that the 3 trees we have used today
don't mean a thing to your well meaning agenda. You
my friend are a well-meaning person who has their
life in reverse and in fact waste more energy than
you save! --
Allen
Ross,
Rockport, Texas, May 2006
This misses the point. The idea
isn't to get your electrical use down to
zero, it's to simply reduce
it. If you were fat and lost 10 of your 300
lbs. would you consider yourself a failure
because you didn't lose all 300? Of course I use
a computer. The fact that I employ the various
energy-saving techniques described on this site
means that still I use far less energy overall
than most. When your monthly electrical
consumption gets down to 150 kWh like mine then
feel free to write again. :)
My laptop computer runs
for five hours on a charge. Does it take more
electricity to recharge the battery when it's dead
than it would have taken to run the computer off
the power adapter for those five hours
instead? --
Barry Smith, Mar. 2005
Yes, a little bit, because transferring
energy from one source to another is always less
than 100% efficient. But the difference is
not significant. It's not worth measuring.
Will a surge suppressor
protect my computer against a lightning
strike? --
Anonymous, Jan. 2005
Your question really isn't about
saving electricity but I'll let it slide
this once.
The answer is no. No surge suppressor you
can buy will protect against lightning, which
can be thousands or even millions of volts.
But some surge suppressors come with a warranty
that covers lightning damage, even though they
can't protect against it, because the
manufacturers are trying to get you to buy their
product. They know the chances of lightning
getting into your electrical lines is rare so
their risk in offering that kind of guarantee to
you is small. If you don't already have
insurance to cover your electronics equipment
then buying a surge suppressor that comes with a
lightning guarantee is an easy way to insure
yourself.
Whether or not you're insured (and whether
with real insurance or a product guarantee), the
only way to keep your equipment safe during a
lightning storm is to physically unplug it from
the wall. Turning it off isn't good enough, and
turning off the power strip it's on isn't good
enough -- there's enough power in a lightning
surge to jump the little gap that turns a switch
off. It's up to you whether you want to go to
the hassle of unplugging your electronics when
there's a storm. Me, I usually leave everything
plugged in and just make sure my computer data
is backed up.
If I just turn off the
monitor at the switch (the monitor button) with the
computer still running will it save
electricity? --
Anonymous, Dec. 2004
Yes, but there's an easier and
better way to do it. Go into your computer's
Control Panel or Settings [In Vista, Start
> Control Panel > System & Maintenance
> Change when the Computer Sleeps ], and
set the screen to automatically turn off when
you're not using it. In fact, you should set the
computer to automatically sleep also so that it
saves energy too.
The monitor uses electricity separately from
the computer (about 35-80 watts), so turning the
monitor off (or sleeping it) does save
electricity, but if the computer is still
running then it's still using whatever it was
using before you messed with the monitor. When
you turn off the monitor you might as well sleep
the computer too, and save energy there as
well.
I heard that laptops
still use energy through their transformer, even
when they are turned off. Is this true, is it best
to unplug the laptop overnight?
--R. Larsen,
Guatemala, Nov. 2004
The transformer for my Apple PowerBook
G4 doesn't use any electricity when the computer
is off. I don't know about other models, but if
they do it will only be about 1 or 2 watts. It's
easy to check -- if the transformer is warm,
it's drawing electricity.
I am in 11th grade at
Seattle Lutheran High School. Yesterday I asked my
science teacher why he leaves his computer on at
night and never turns it off. He said it was too
much of a hassle to turn it on and off every day
and that one person does not make a difference. I
thought that was a bad attitude but i didn't tell
him he was wrong because I did not have any proof.
I found your website and i am going to give him
some stats on keeping his computer on 24/7. What I
found out is that by keeping his computer on 24/7,
he wastes 499,200 kilowatts a year! My question is:
could you tell me what other things those 499,200
kilowatts could be used for. Maybe those watts
could be used to power tools during surgery or
something like that. Also, he is into saving the
environment, so how could saving those kilowatts be
good for the environment. Thanks so
much. --Maya
Sears, Jan. 2004
Your science teacher at your
Lutheran high school said it was too much of a
hassle to turn his computer off at the end of
the day? Some Lutheran he is. Anyway, good
for you on trying to help save electricity! You
are right, one person does make a difference. If
you look on the front
page of my site you'll see a link to a
calculator which will show you how much
pollution is generated to power your teacher's
computer overnight. To use this calculator
you'll need to first figure out how much
electricity the computer uses, and I'm afraid
your calculations are off. First, it looks like
you calculated watt-hours, not kilowatt-hours.
You have to divide watt-hours by 1000 to get
kilowatt-hours. You might have also assumed the
computer is not in sleep mode overnight which
uses less electricity, although it probably is.
Energy use varies a lot from computer to
computer, and if the computer is in sleep mode
then it uses even less energy. You can find out
exactly how much the computer uses by using a
watt-meter. You might
also be able to find out on the manufacturer's
website how much it uses in sleep mode. If we
just assume the computer is in sleep mode and
uses 25 watts, and that it's on for an extra 17
hours a day, that's 17 x 25 = 425 watt-hours per
school day. If it's on 24 hours a day on the
weekends, then that's 24 x 25 = 600 watt-hours.
So for the whole week we have (5 x 425) + (2 x
600) = 3325 watt-hours per week. For a school
year of 39 weeks, that's 39 x 3325 = 129,675
watt-hours. There are 1000 watt-hours in a
kilowatt hour, so that's 129.7 kWh.
Using the calculator link, choose
"Commercial" and keep putting in a smaller
dollar amount until the kWh gets down to 130
kWh. Then you'll be able to see how much
pollution is caused by the computer being on
overnight.
As to what else that energy could be used
for, the answer is "anything that uses
electricity", but that's not the best question.
The reason to use electricity is not so you
could use the electricity for something else,
it's so you can decrease pollution and save
money. Good luck!
My brother leaves the
computer on 24/7. He told me that his friend told
him that when a computer is idle it burns as much
energy as a watch battery. I didn't believe this
since a watch battery produces electricity. What do
you think? -- Chris O'Neil, July
2003
You can find this kind of info yourself
on this site. Information about how much energy
is used by computers and how much is stored in
household batteries is on the "How
do I find out how much electricity something
uses?" page. But let's tackle your question
here anyway in the interest of dispelling some
myths.
First of all, batteries don't produce
electricity, they store electricity.
(Technically, they store energy, but
let's not split hairs.)
Second, you're right that comparing a
computer to a battery is an invalid comparison,
but for a different reason: a battery stores a
fixed amount of energy, but the amount of energy
used by a device increases the longer it's left
on. In other words, the comparison fails to
consider time. It's like saying "My cat
eats as much cat food as is in that bag." Sure,
but over what period of time? An hour, a week, a
month? Similarly, a computer will definitely use
as much energy as is in a battery; the question
is how long does it take to do so?
Third, a computer that's "idle" is not the
same as one that's in sleep mode or on standby.
Sleep/standby put the computer into a low power
state which saves electricity. If the computer
is simply idle (not being used) it won't save
any electricity at all.
So let's see how long it would take a
computer in sleep mode to burn through the
energy contained in a watch battery. According
to Watch
Batteries USA a typical button battery is
1.55V and 105mAh (0.105 amp-hours), and as we
know from our earlier page "How
do I find out how much electricity something
uses?", we just multiply volts times amps to
get watts. So 1.55V x 0.105Ah = 0.16 watt-hours.
Also from our How do I
find out... page we see that a sleeping
computer uses about 22 watts. So a sleeping
computer would use the energy contained in a
watch battery in 0.0073 hours (0.16/22), or less
than thirty seconds.
I work for a company
that has over 100 computers in its offices and
production areas. One of our MIS people tells me
that is is not a good idea to turn our computers
off during the night and on weekends because it
puts extra stress on them to turn them off and on,
that you are shortening the life of a computer and
monitor by repeatedly starting it. Do you know if
this is actually true? -- Janet
Smith, April 2003
Your MIS people are wrong.
You're not going to wear out your computers
prematurely by cycling them off/on overnight and
on weekends. This is just an urban myth. Modern
computers are simply not that fragile. (By the
way, I did technical support at Apple Computer
for five years, so I have a background in
troubleshooting computer hardware.)
The useful life of a computer these days is
only a few years anyway. The computer will
become obsolete long before you wear it out, no
matter how often you cycle it.
Something else to consider is that all
devices eventually wear out after running
for a long period of time. Keeping your computer
on constantly means it's running three times
longer than normal. This extra running time is
at least as likely to wear out your computer as
turning it off at night. For the monitor, it'll
definitely wear out quicker by keeping it on
rather than turning it off.
Even if turning a computer off once a day
shortened its overall life by a few days, it
wouldn't pay to keep it on all the time. Your
hundred computers are costing your company
several hundred to several thousand dollars a
year in energy costs if they're not being turned
off at night.
If a computer is used from 8:00 to 5:00 on
weekdays, then it's not being used for 16 hours
a day during the work week, and 48 hours for the
weekend. That's a total of 128 hours a week, or
6656 hours a year. At an estimated 25 watts/hr.
in sleep mode, that's 6656 x 25 = 166,400
watt-hours per year, or 166.4 kilowatt-hours per
year. At $0.10 a kilowatt-hour, that's
$16.64/year.
That's for just one computer. For a hundred
computers it would be $1664/year. If the
computers aren't in sleep mode, then at 150
watts/hr. it's more like $9,984/year.
And then there are the hidden costs.
Computers generate heat, and your company is
paying a pretty penny for air conditioning to
remove all the heat generated by computers that
should be off when they're not being used. And
if the AC doesn't run overnight and on weekends,
running the computers in a hot environment will
do more to shorten their lives than turning them
off once a day.
Bottom line: Turn your computers off at
night, and don't worry about it.
Here are some articles with more detailed
information on this topic:
Postscript: An MIS person told me they want
the computers kept on overnight at his facility
so they can install software updates over the
network. Updates installed during the day would
slow down the computer while someone is trying
to use it. But companies that do this pay a big
penalty in electrical and cooling costs. For
companies that must do this, there's probably
software that puts the computer into standby
(sleep) mode after installing updates, or if
there are no updates to install that night.
I have my computer on
from about 9 AM to midnight. My question: Would I
save electricity if I use sleep mode instead of
just sitting with a screen saver going?
-- Louise
Gullion, 2-02
Yes, that's what Sleep mode is
for. A screen saver that puts images on the
screen doesn't save any electricity, since the
monitor and computer are still active. You save
electricity only if the monitor isn't generating
an image and the computer isn't thinking.
Putting the computer to sleep puts both the
monitor and computer into very-low-power mode.
We have a visitor in
the house who chats on the Internet every single
day from about 11:00 p.m. until 7:00
a.m....yes....8 hours straight every day.... My
electricity bill doubled last month...could it
possibly be from the extra use of the computer?
Shall I kick him out?
-- Kathie
Myers, 1-01
Your visitor didn't double your
electric bill, unless your bill was about $3.13
a month before (s)he moved in.
A typical desktop computer uses about 65
watts plus another 80 watts for the CRT monitor.
The How much it costs
section explains how to figure out how much
you're paying for electrical use. For example,
145 watts of computer equipment times 8 hours a
day times 30 days a month is 34,800 watts, or
34.8 kilowatts. If you're paying 9¢ a
kilowatt hour, your friend's computer use is
costing you $3.13 a month.
Your bill might have gone up because of a
rate increase. Did you check to see if the
amount of electricity you used went up
(kWh), or just the amount you paid?
Energy is getting increasingly expensive, as the
world is running out of cheap fossil fuels.
I've heard that when
you start up a computer it uses the same amount of
electricity than it would if left on and casually
used for a week. I've also heard that PC's consume
ridiculous amounts of power even on energy saving
mode. Is it better to shut down the computer or use
energy saving mode? I've heard that having a higher
refresh rate and resolution on a monitor coupled
with a higher performance computer (megahertz,
etc.) uses more power. Is there a significant
difference between desktop to desktop?
-- Y. Gonzalez,
Miami FL, 2000
(1) It doesn't take any extra
electricity to start up a computer. You can
verify this by measuring
the consumption, as described on this site.
(2) Energy-saving mode does save
power. That's what it's for. The amount saved is
listed in the specifications for your computer,
or you can measure it using the methods
described on this site.
(3) Shutting down obviously saves more
electricity than energy-saving mode, but it's
inconvenient to have to wait for your computer
to start up after a shut down. Probably the best
compromise is to shut your computer down at the
end of the day and turn it back on the next day
(and use energy saver throughout the day when
you're not using it).
(4) Monitor resolution and refresh rate don't
affect electricity use. Yes, faster processors
use more power but you'll have to measure
it yourself if you want to compare two
different computers. The biggest difference is
that the newer computers with flat-panel LCD
monitors (like on the newest iMacs) use a lot
less electricity than traditional CRT
monitors.
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