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I'm using a notebook as my only computer and I'm wondering how I might save the most energy (in terms of my electricity bill).
Will it use less energy overall to only plug it in if the battery is low and unplug it as soon as the battery is loaded? Or is it better to leave it plugged in until I'm done using it?
Benedikt
Posted 2011-07-21T19:27:08.530
Reputation: 199
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It's insignificant. Find better ways to save energy.
Your typical laptop consumes less electricity than one average light bulb.
This is a brilliant case of being penny-wise, pound foolish.
Laptop = 15-60 watts. Light bulb = 60-150 watts Fridge = 200-700 watts Dishwasher = 3500 watts Clothes dryer = 4500 watts ...
Are you planning to turn off your fridge every time it's cold enough and turn it back on just in time to avoid spoiling your food?
Energy saving should be an analytical activity. First, identify WHERE most of your energy footprint comes from, THEN figure out ways to reduce it. Don't fall for feel good, knee jerk measures.
Edit: Following your comment about electricity prices in Germany, here are some REAL numbers for you to think with:
Assuming 4 hours per day, 365 days per year, with a laptop consuming 50 Watts, you are using 76 kWh per year.
According to https://secure.wikimedia.org/wikipedia/en/wiki/Electricity_pricing:
1kWh = $0.306 (Germany - 2009).
76 x 0.306 = $22 per year.
If, through great efforts on your part, you saved 30% of your laptop energy consumption, you would reduce your yearly electricity bill by $7.
Do you really feel it is worth it?
Sylverdrag
Posted 2011-07-21T19:27:08.530
Reputation: 509
It's just one tiny piece of my general energy saving plan which checks anything that's consuming energy in my household. And that also includes the laptop. – Benedikt – 2011-07-22T11:12:45.480
@user9673, In all fairness, you can't easily buy what you call "one average light bulb" in the USA any more, only fluorescents or LEDs that use much less energy. Benedikt, our generically-named friend's point is a good one: the time you spend trying to reduce laptop energy usage could be more effectively spent on higher-impact tasks like, say, shopping for a fuel-efficient auto (if you drive). For one hour of your life invested, you have to consider the return. – CarlF – 2011-07-22T12:24:19.770
@Benedikt: Well, have fun with that but as far as your electricity bill is concerned, you wouldn't notice the difference if you were to stop using your laptop completely. It looks like your concern is money. If that's the case, you should consider that spending hours of your time to save 15cts of electricity per year is possibly not the best way to improve your financial situation. – Sylverdrag – 2011-07-22T12:50:54.973
Sounds a little bit like you don't know the electricity costs in Germany ;-) – Benedikt – 2011-07-23T06:16:04.477
@Benedikt: of course, my comment was tongue in cheek, but the point remains. I have updated my answer to give you some realistic figures to think with. Tell me if you think it's really worth your time. – Sylverdrag – 2011-07-23T14:00:11.053
Agreed. A laptop draws so little current it's not really worth worrying about unless you're "off the grid" and relying on solar power or some such (which they do, I suppose in Germany, but not on the same scale). The main thing you can do to save energy with it is to set it to sleep or hibernate when you shut the lid, and then shut the lid when you won't be using it for an hour or so. – Daniel R Hicks – 2011-08-07T20:01:45.573
I'm the most energy savvy in my family, but my laptop is turned on at least 12 hours a day (I work in the laptop), and my mobile phone is turned on 24/7 (and drains the whole battery twice a day, I often browse/game in it); my sister has a desktop (which she keeps running 24/7), a laptop, two mobile phones (24/7), and an iPad; my mom has a laptop, a netbook, and two mobiles; my dad has a desktop and two mobiles. The total energy consumption sums up to almost the same as running a fridge. And no, we don't run on incandescent light, a CFL uses 12 watts and are brighter and whiter. – Lie Ryan – 2011-08-11T09:29:32.730
@Lie Ryan: 12 hours a day, 365 days a year? You are most likely overestimating badly the case, but even in this extreme situation, you are talking about $66 of electricity per year total your main work tool (same for me), and a potential saving of $21 per year on the laptop, less than $2 per month. – Sylverdrag – 2011-08-11T09:58:39.440
@Sylverdrag: I'm not overestimating, in fact I'm probably underestimating (but I don't want to sound like I live off of the laptop, although in fact I do); as long as I'm not sleeping, the laptop is on. Even when I'm on the bus or the train, the laptop is on and the mobile phone is tethering. – Lie Ryan – 2011-08-11T11:11:24.223
@Lie: Write a small app to record the time it is on and active (not in sleep mode) and you might be surprised by the result. I am also a major laptop user (I even sleep with the bloody thing next to my bed). Anyway, I have no intention to challenge your usage. It is what it is, but still doesn't look like a significant expense item. – Sylverdrag – 2011-08-11T16:11:12.123
Skim read, and haven't read comments - sorry if someone mentioned it... You also have to consider that if you constantly run the battery down and recharge, it will shorten the life which most likely would of been the whole point of getting a laptop in the first place, and the cost of a replacement battery may be more than the electricity you saved! – William Hilsum – 2011-08-12T19:59:41.580
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To answer your actual question: discharging and recharging the battery, all other things being equal, will use more power than just being plugged in. Some energy is lost in the actual battery-discharge and battery-charge processes themselves, in addition to whatever you're actually using to do stuff on the laptop.
Other answers give good advice about how to actually lower your energy use.
CarlF
Posted 2011-07-21T19:27:08.530
Reputation: 8 576
2+1 for actually answering the question of discharging/recharging the battery -- the answer is that it uses more power than leaving the charger in when in use – Soren – 2011-08-11T03:04:34.907
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Lie Ryan
Posted 2011-07-21T19:27:08.530
Reputation: 4 101
3I am downvoting this because, while everything you say is perfectly correct, the end result is a major hassle and it saves almost NO energy at all. The saving is insignificant. Doing what you recommend is like hunting down text files below 50kb on your computer and deleting them to "save space". In absolute terms, yes, you reduce the energy consumption. In practical terms, you are wasting your time and making life harder for yourself with no upside at all. If you were to turn off completely your laptop, I bet you wouldn't be able to spot the difference on your electricity bill. – Sylverdrag – 2011-07-22T06:13:59.740
2@Sylverdrag -- seems unreasonable to down vote the answer just because you disagree with the question -- there is nothing wrong with the question either when viewed objectively, however your argument of "is it worth it" is probably very fair (I don't think it is either) but that should not affect the correctness of the Q&A -- however this answer does not answer the specific OP question of discharging/recharging the battery. – Soren – 2011-08-11T02:59:11.323
@Soren: I downvoted it because it is a terrible advice to the OP. Seriously, would you recommend to turn the brightness down to save about $1.50/year? Will this benefit the asker? Potentially hurting his eyes and causing headaches for $1.50? Terrible advices should be downvoted, even if they are technically correct. Another example: SSD. Seriously? The guy is trying to save money and you are going to suggest SSD? The difference between a regular hard disk and a SSD is more than the consumption of the device over 10 years! No external keyboard/mouse? $0.10 per year. – Sylverdrag – 2011-08-11T05:07:33.683
1@Sylverdrag: some of the advice is battery saving tips, which will also prolong the life of the battery, and since a lot of people dump their laptop when their battery no longer holds charge, prolonging the battery life will prolong the life of the laptop. And I do have a headache if I turned my brightness all the way up in the night. Also, half of the tips are about ensuring that you have the proper energy saving settings, there is no hassle to you at all apart from going to the Control Panel. – Lie Ryan – 2011-08-11T09:51:21.297
@Lie Ryan: By default, reasonably savvy people adjust brightness to a comfortable level. You might like it darker than I do, but that's not the point. Going below that comfortable threshold causes trouble, whatever the threshold is for the individual. Lowering CPU speed = lowering both consumption and performance. If you didn't need the performance, it's no problem. If you do however... Using a smaller laptop also reduces usability and performance. Dual VGA card, cool. There goes another $3 per year. SSD of a decent size. Oups, all the cents you saved for the next 50 years are gone. – Sylverdrag – 2011-08-11T10:09:02.847
@Sylverdrag: I used to have my screen on full brightness all the time even when it hurts my eye, in fact I get so used to the eye hurting that I didn't notice it. Another thing I noticed is that if you turn down the room's brightness, you can also turn your monitor's brightness down without hurting your eye or having the screen too dim. Most people have a CPU that runs faster than they need to get comfortable performance, I only need to run CPU on full speed when compiling (and in any case, this optimization is automatically done by the OS, as long as you have the proper setting). – Lie Ryan – 2011-08-11T10:54:39.877
@Lie: But all this comes under the heading of properly setting up your computer. Let's not delude ourselves into thinking that it makes a meaningful difference in terms of costs saving, which is what the OP is talking about. – Sylverdrag – 2011-08-16T15:24:13.700
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Type "cmd" on your "search for programs and files" and run the following command: powercfg -energy
After 60 seconds the program will create a html file that describes the possibilities to save battery consumptions and consequently energy.
Diogo
Posted 2011-07-21T19:27:08.530
Reputation: 28 202
3Assuming the OS is Windows – Linker3000 – 2011-07-21T19:45:33.570
But does the notebook consume more energy if it's loading or if it stays plugged in when the battery is fully loaded? – Benedikt – 2011-07-21T19:50:43.640
Exactly, the question didn't specify. – Diogo – 2011-07-21T19:51:05.517
2Every single device on your notebook consumes energy, specially LCD and Wifi, the better you can do to reduce power consumption is turn off them(if you are not using wifi, turn off it, and if you are away from keyboard, set your Windows to turn off your LCD in few minutes, like 2 or 3). Your Processor and hard disk also consumes a lot of energy, however, most of current processors have the speedstep feature, that underclocks your processor on idle states; your hard-drive also can be turned off by your Windows when idle. Most that is possible will be given by the html genarated by the command. – Diogo – 2011-07-21T19:57:49.103
1Upvoted because it's a great tip, but saving energy on laptop while plugged in is a fool's errant. – Sylverdrag – 2011-07-22T06:29:49.873
@Linker3000: It's a fair assumption, considering more than 80% of computers are running Windows. – music2myear – 2011-07-26T21:49:23.623
C:\Users\danh>powercfg -energy Invalid Parameters -- try "/?" for help – Daniel R Hicks – 2011-08-07T20:03:54.400
@DanH: Maybe something is happening over your O.S. All machines I tested it worked correctly and anyone I seen had the same problem. You should reconsider your downvote. – Diogo – 2011-08-08T02:17:23.020
@DanH are you sure you spelled the command properly? – nhinkle – 2011-08-08T02:21:46.760
I copied/pasted directly from the cmd window. (Can't reproduce the line break in a comment, of course.) (What downvote?) – Daniel R Hicks – 2011-08-08T02:54:25.037
Which version of Windows are you using??? Im using Windows Seven. Maybe it is not avaiable on Windows XP. – Diogo – 2011-08-08T11:44:29.470
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Will it use less energy overall to only plug it in if the battery is low and unplug it as soon as the battery is loaded?I don't know if that will save energy or not, but that will quickly kill your battery life. – Lie Ryan – 2011-07-21T19:50:33.493