Computer Power Usage written 12 years ago

Power Socket

Apparently, the british government is to outlaw standby buttons on consumer electricals in an effort to reduce power wasted around the home. This got me thinking: just how much energy do everyday appliances use?

Power MeterA little bit of googling found me a power meter, which would give a digital readout of the amount of electricity being used by an appliance. The geek in me couldn’t resist, and one was aquired the very next day.

Computer Power usage

My computer is nothing special, infact it’s pretty decrepit by today’s standards:

The results below are for the Speakers, Monitor and computer system. I decided there are essentially three states my machine can be in: “Off”; Sleep and On.

Device “Off” Sleep On
Monitor 1w 1w 20w
Computer 11w 12w 152w
Speakers 4w 4w 10w
Whole System 15w 18w 190w
Info “Off” means that the computer is switched off, but still plugged in. “Sleep” is using S3 standby. Monitor in standby mode, and speakers switched off. “On” is at the computer’s normal state, with the monitor at average brightness, and with some music playing.

What suprised me here is the amount of energy that’s needed, even when the computer is “off”. The 11 watts is needed by the computer are to power stuff like Wake on Lan, and Wake from USB, which is needed to power the computer on by remote. It’s still an insane amount of energy, and makes me feel much better about leaving my computer in sleep mode most of the time — since it only uses 1 watt more.

Another suprise is the speaker system, in that even when the pushbutton to turn it off is pressed, it’s still using as much energy as if it was left on!

I also checked the family computer to see how much power that used. I’m not sure of the spec, but it’s something in the order of a 700mhz pentium. These values are for the entire computer system (computer, CRT monitor, printer, scanner & NTL Modem).

“Off” Sleep On
20w 45w 126w

A bit more poking revealed that the scanner, which had no on/off button was actually sapping 5watts just by sitting there, waiting to burst into life. This accounts for the rather obscene amount of power used when the computer is “off”, being generated by the flickering lights on the cable modem, and the scanner being greedy.

Other Appliances

After finding out how much the computer used, I poked the other appliances in my house to find out how much energy they used:

Stand-by On
Clock Radio 1w
Phone Charger 0w 2w
Kettle 3102w
Set Top Box 7w 7w
TV 7w 60w
60 watt Light Bulb 60w
Hi-Fi Micro system 6w 15w
TV Aerial booster 1w

What’s of interesting note here is that the Digital Set top box uses the same amount of power in standby as it does in fully operational mode. Even though it appears to have 2 “off” modes, they all use 7w, which seems a little silly.

Unsuprisingly a 60w bulb uses 60w, no issues there.

Things like the kettle though are a little frightening, it’s using over 3kw of power, at close to 13 amps — the maximum amount of juice a household appliance can use. I suppose 3kw for 60 seconds x 10 a day soon adds up!

Usage costs

Assuming that electricity costs 10p / kwh, we can come up with some guesstimates as to how much certain appliances cost to run per year:

Device Kwh / year cost
Kettle with 8 boilings a day for 1 minute. 150kwh ?15.10
Set top Box 24h usage. 61kwh ?6.13
Computer 6hrs usage / day, rest of time asleep. 534kwh ?53.44
Clock Radio 24h usage. 8.76 ?0.87
Power Shower 5kwh, 15 mins daily 456kwh ?45.62

So crikey, I always wondered if having a computer made a noticable increase in the electricity bill, and it looks like it makes up quite a significant part of it!

Comparing these numbers to those of an Apple iMac, which runs at around 60w when under load, and next to nothing in sleep mode, it’s pretty astounding. It’d only take a few years for the apple to pay for its own premium in terms of reduced energy bills!

And so?

I wouldn’t say playing around with this device has changed the way I look at energy usage too drastically, all the numbers were around where I expected them to be. Some things have suprised me, like the stupidity of the Set top box, but I’ve also been relieved at how little the computer uses when in sleep mode.

The costs however have frightened me quite a lot! Using over 1kwh a day on a computer seems a little crazy.

Considering the numbers here, it’s quite obvious why the world is heating up, and we’re all swealtering in the heat, but I can’t see any of this changing any time soon. We’re all far too accustomed to our luxuries.

← previous entry | next entry → Fri 21st Jul 2006 - 09:01 | 15 comments | tagged with Real World, Essays, Computery Stuff

 Comments 15 comments made

Wow, im impressed with the ammount of research and effort that went in to this post. Some surprising results there.

Wow, that is quite shocking, especially the usage when the damn things are turned off! I’m starting to get electric tight since my electric bill seems to be gradually getting higher, everything is turned off at the plug now, except for the alarm. But the kettle thing really surprised me, I’ll have to cut down on the tea, although I don’t think I drink 8 cups a day. Still, nice work Robness xxxx

Jordan Lee’s GravatarJordan Lee 1 year later

Hi. My name is Jordan Lee. I am a university student in Edinburgh. I just got a bill of 200 pounds for electricity charges over two months!

I would like to ask you a question.

1) When the red ‘on’ click is left on for the power switch (rather than the red ‘off’ click), does that mean my kettle which is left in the switch (for the matter of convenience) is still eating the same amount of energy, as if I was actually heating up water???

originally posted by Jordan Lee

1) When the red ‘on’ click is left on for the power switch (rather than the red ‘off’ click), does that mean my kettle which is left in the switch (for the matter of convenience) is still eating the same amount of energy, as if I was actually heating up water???

Your kettle will only be using electricity when it is heating water. It’s one of the few appliances with a binary power state - it will either be on or off.

Your bill of 200 is an insane amount of electricity! I would first check for mistakes on the bill — be sure to give the electricity company the meter readings from when you moved in, and the current readings. They will often send you an amended bill.

If it turns out you have spent 200 on electricity you need to go pin your housemates down and find out which one has had an electric heater on 24/7….

Jordan Lee’s GravatarJordan Lee 1 year later

Dear Rob,

Thanks for your quick response. You seem quite knowledgeable on the subject. My flatmate and I just talked to the scottishelectric power, and they say our bill is correct.

We are currently trying to locate the expenditures of energy to account for the collosal bill. Actually, we are going to pickup a powermeter to experiment around the flat and to see the types of consumption we do.

Can I ask a really main question in our minds: When appliances (non-kettles which you said were binary state power) are left in the plugs, with the red ‘on’ click on does that mean that we are still consuming considerable amounts of energy? (I fear we actually do) Having that been said, when you mentioned the electric heater, we have typically left the main power sources feeding the heater on the red ‘on’ click but the heater device switch off when we are not using it, does that mean that we are still consuming considerable amounts of energy for the heater? By the way, we have traditionally the red ‘on’ click feed source of our electric stove on, does that mean that 24/7 we had been consuming considerable amounts of energy even though we were not cooking food on it.

Your reply would be greatly appreciated.

Thank you. Jordan Lee. Edinburgh.

Jordan Lee’s GravatarJordan Lee 1 year later

I forgot to ask you about battery powered devices like for example large flashlights etc.

should I take out the batteries from the device, while its sitting around for weeks on end without use? (How much energy is consumed on the ‘idle’ state here for these devices)

originally posted by Jordan Lee

… we are going to pickup a powermeter to experiment around the flat and to see the types of consumption we do.

A good idea — and will easily answer your questions on power consumption.

When appliances .. are left in the plugs, with the red ‘on’ click on does that mean that we are still consuming considerable amounts of energy?

Although when appliances are left switched on at the socket, but in an “off” state they will use some power, usually it’s very little power. Appliances such as your cooker and heater shouldn’t use any power when off, and it’s very easy to tell if they are — they’ll be hot!

Doing some quick maths:

200 is approx 2000 kw hours of electricity, and spread over 2 months that works out as you using an average of 1300 watts every hour. To put this into perspective, your computer uses around 150watts, TV around 70watts and the average alarm clock uses 1 watt. So to use 1300 watts really is insane, and won’t be caused by leaving things on stand-by, or left switched on when not in use.

The most likely cause is your heating, which I’m guessing will be electric. You should check that you’re only heating the house when you’re there, and not leaving it on all night (when you’re snuggled up in bed). The other issue is that your house might be old and crappy, and leaking heat. Not much you can do about this, except whine to your landlord.

Unfortunately with winter on the approach, your heating bills will only go up, so you’ll need to be ultra frugal with the heating, and invest in plenty of woolly jumpers !

So in summary, it is unlikely devices left on standby will be your problem. It’s most likely your heating, that’s your main usage of electricity.

With regards to your question on battery powered devices, it’s a fair bit tricky here. The power used whilst idle isn’t the problem — it’s the batteries themselves.

Most rechargeable batteries will discharge themselves if left untouched for a period of time, and some will even corrode and release ‘orrible chemicals if left for a long time. The best “all round” plan is to try to keep using them, and never leave them for long periods of time without being used and recharged.

If you know you’re not going to be touching something for a number of months, then it’s definitely better to remove the batteries — mainly to stop them corroding and making a mess of the torch or whatever they’re in.

Janet’s GravatarJanet 1 year later

Thanks for this research. I understood about kettles etc, but the computer had me wondering. Now I’m clued up!

Dale’s GravatarDale 2 years later

Hi there,

Im having abit of a chrisis with the parents here regarding having the computer on 24/7.

ive read all over the net about it, and some say its better to leave it on because it doesnt use as much power been on thatn it does powering up:

http://answers.yahoo.com/question/index?qid=20080426151627AAdA1go

http://answers.yahoo.com/question/index?qid=20070515144713AAVrIeJ

when left on, its just downloading/uploading or just on running programs, my Dad seems to think its sucking watts out of the wall, and he demands that its turned off when i leave the room, (i went out the room for 5mins, came back and he’d unplugged it). i cant tell u how much the bill is each month because i dont know. I have read your piece, and read others too, both saying 2 different things. But does anyone actually know?

i really need help here in trying to get him to understand that the PC is not sucking out all this power! like boiling the kettle 3 and 4 times a day is more right??? and the fridge/freezer been on!

can you help, or anyone help me on a serious anwser to show him?!?!

Someone PLEASE HELP ME!!!

Thanks you so much, Dale

originally posted by Dale

ive read all over the net about it, and some say its better to leave it on because it doesnt use as much power been on thatn it does powering up:

This is wrong I’m afraid. Doing some sums it’s easy to see:

  • Let’s say when your computer is powering up, it uses the maximum power available to it. Say 500watts. (this is a gross overestimation), and takes 1 minute to boot.
  • When your computer is on it is using around 150watts.
  • When it is off it is using around 10watts.

And let’s say you use the computer four times a day for one hour each session.

  • If you were to leave your computer on for 24 hours, you would use 24 150w = 3.6kwh
  • If you were to shutdown after each session; (4 150w) + (4 1/60 500w) = 600 + 33.33 = 0.6 kwh

So even with the wild numbers assumed for how much power your comptuter uses for startup, it’s still nowhere near as much used in 1 day.

when left on, its just downloading/uploading or just on running programs, my Dad seems to think its sucking watts out of the wall, and he demands that its turned off when i leave the room,

Well, leaving the computer on 24 hours a day uses 3.6kwh, which is equal to ~36p per day. That’s 131 a year.

I really need help here in trying to get him to understand that the PC is not sucking out all this power! like boiling the kettle 3 and 4 times a day is more right??? and the fridge/freezer been on!

Sadly, your computer is sucking out power, as above it will be using over 100 a year to keep it on 24 hours. The table in the article shows you how much boiling a kettle 8 times a day, and that’s only 15/year.

There’s not a terrible lot you can do about this really. Ensuring your monitor goes to sleep within a short period of time will help. What about a laptop? they typically use less than 20watts.

Another alternative, for your downloading needs is something like this: Emprex NSD-100 P2P Download Engine

Which is a low power device you can buy that will sit and do your downloading all day and not cost your dad a fortune. Persuede your dad to get one of these and he’ll be quids in. Perhaps promise to do the washing up too eh?

Dale’s GravatarDale 2 years later

Hi Rob,

Thanks for the fast response!

well 36p a day is nothing, but yes it does add up, and to be honest, its not on like everyday of the year, but a fair amount of the year. it will be off mybe 2 or 3 nights of the week, other than that its left on.

I do have a laptop also, which i use on a regular basis when not on the PC, even though he thinks this is sucking power out the walls too… when really its only charging the battery. On an evening i will use the laptop more than the PC, i will either leave the PC on while it downloads, or 80% of the time Hibernate it and download on the laptop. i always turn of the moniter and speakers when i turn off/hibernate the PC.

Either way, he STILL doesnt realise how much these things use, he thinks its draining the powerplant…even hiw PC will use more than mine, his is older with a CRT moniter…and he’s on that everyday!

Thanks for your help Rob, Look forward to the reply,

Dale

Alex’s GravatarAlex 2 years later

wow, some very interesting reading, its quite shocking to think about kettles, in our house its boiled 20-30 times per day (being British ;D)

And as for computers, im definately going to turn mine off when i go out now!!

Steven’s GravatarSteven 2 years later

The bit most people miss is your computer and most people may have 1 or 2 used 534kw/yr (used for approx 6 hours), however your shower (would be used everyday) and uses the same in only 15/20mins of usage, what happens if there is 2,3,4 in the household showering once a day!! Check your shower power outputs most showers are betwwen 8.5kw and 12kw /hr. This is where a vast proportion goes, fan heaters are about 5kw/hr, tuble dryers about 2/3 kw/hr.

Steve

George’s GravatarGeorge 2 years later

Quiet a posting and amount of work you have put into this. Have a question. We are going to Clearwire for internet and wireless phone and have found out that we have to leave our computer on 24/7 for the phones to work. Any idea how much more electricity this will require and how it will shorten the life of our Compaq?

MACK’s GravatarMACK 3 years later

SOMETHING TOTTALLY DIFFERENT: GET ELECTRICITY FROM AIR! INTERESTED? I AM WORKING ON A DESIGN BUT NEED TO KNOW

1—- HOW MUCH ELECTRIC POWER IS NEEDED IN A TYPICAL 4 BED HOUSE WITH A LOT OF ELECRICITY USING GADGETS E.G. LIGHTS, HEATING, KETEL AND SO ON.

THIS WOULD DETARMIN THE SIZE OF MY MACHINE… MACK CAN CONTACT ME WITH THE E-MAIL PETROMAX51@HOTMAIL.COM

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