Laptops energy consumption: save or not

Laptops energy consumption: save or notPopularity of Laptops increases from day to day. Today not only businessmen who need possibility to work in any time and any place buy laptops but also ordinary users. Laptops are bought as the home PC and for work in office.

Not big mobile computer will be the good partner during traveling. It helps to post the latest photo from the sea in blog, and to communicate with colleagues.

This article is for that people who time from time use one of the best laptop's features: mobility, or accurately ability to work without net during some time. Many people know that less difficult operation on the mobile computer and less loaded its components then more time will functional its accumulator. But not everybody knows these operations that are more power-hundry for a laptop. In this article we will try to answer for this question.


We will describe this question with the help of 17 different test sceneries that tested laptops in different work conditions. The first test is our standard. Mobile Computer is turned on. There are not any operations. All wireless interfaces were turned off. Max energy save mode was turned on (for min processor and video card frequencies for hard disk were turned off in 5 min of inactivity). Brightness of monitor was set to min (but the display was not turned off!). Just in this mode laptop is able to functional more time. Therefore in all diagrams we will compare all tests with this one.

The second test distinguishes from the first one with only one characteristic ??У the display brightness was set to max. So this test will perform the possibility to understand should we spare on the display brightness. In the other tests it set to min.

Next group of tests (3 tests) verify the energy consumption during the max processor load, RAM and video card. For the processor boot CPU Burn-in utility was used. Both cores were loaded. RAM was loaded with the use of benchmark that is built in PCMark 2005. And Video Card was loaded with the use of graphic tests (only graphic) 3DMark 2006.

In which operations are these three components deal? All operate in games. But video card is loaded more (notably if high definition and high graphic quality are set), then processor and RAM. If you decide to archive data, processor and RAM will be loaded.

The operation with disk storage units is run rarely on laptops. For this purpose we test the time of unmanaged mode with max loaded hard disk (copy different files with one part of Winchester to another) and optical drive mechanism (there were 4 tests: read/save CD, read/save DVD). Notify that while watching a film works the hardware on what it is saved, RAM a little and the processor decodes audio and video flow. Modern video card are able to decode DVD and the most modern - HD Video as well.

The information comes on laptops from outer world through net interfaces or USB. We have 4 test sceneries for this. The first and the second sceneries test how much energy Wi-Fi uses. There is the opinion that wireless net cards minimize the accumulator charge very quickly. So we see how long laptop works when Wi-Fi is turned on and max loaded. Two other tests deal with Ethernet and USB. We copied large files through these interfaces and verify the time of it work. The results were very interesting.

And the last thing ??У is sound. We have three tests on this issue. The first was done when sound was completely turned off (Mute mode was selected in the laptop settings). Why did we do it? We did it to verify the load level of the processor and RAM while music reproduction through Winamp 5.5 player. The second test was done when laptop acoustic system was turned on. The sound level was set to max. The third test is differed from the second by the max sound level was reproduced through headphones.

We suppose that our method covers the majority of the fields where laptops are used. Now, let's view the configuration.

Laptops configurations

We've tested modern but not least laptops. But they are actually today. They do not vanish from the market and the latest modern computers do not greatly better in technical characteristics. Formally, all results will be able to move to the latest models of mobile computers.

Five systems participated in testing. There are their characteristics:

There is the laptop with Celeron M processor in testing. Notice that this chip hasn't a part of energy saving technologies in contrast to Pentium M, Core Duo and Core 2 Duo. So it will be interesting to view as it'll affect the unmanaged mode of the mobile computer.


We perform 2 diagrams for each test. The first includes the absolute tests' results. Blue lines ??У are the results with min loading (for more obvious comparison). Purple lines ??У are the results for the specified test. The second diagram shows the relative results. It is possible to see from them the energy a component consumes in comparison with min loading of the mobile computer.

The time of the unmanaged mode of the mobile computer when min loading


Display is the most important part of a mobile computer. It's used always when we work with a laptop. And sometimes it is difficult to notice the max brightness setting especially during the day under the sun. How does it affect the energy consumption? Let's see the diagram!

The time of the unmanaged mode of the mobile computer when display brightness is 100%

The results are very significant. The difference between min and max brightness is from 15% to 25%, that is 30-60 minutes (versus from the laptop model). There is the first advice for you: set the brightness to possible min for your laptop.

Processor, RAM, Video Card

Processor and RAM are used always too. But their usage depends from the loading of the computer. It should some energy to read or write a text. To edit a big picture in Photoshop needs more energy. Video Card that operates in two-dimensional graphic is needed in a small amount of energy. But Windows Vista interface with three-dimensional switching between windows will affect the unmanaged mode of the mobile computer.

The time of the unmanaged mode of the mobile computer when max processor loading

Processor is angry when it is loaded a lot, and it consumes a lot of energy. Single-kernel Celeron M that is set in Acer Aspire 5315 is the exception. We suppose that all other participant of the testing have double kernel processors. And none of the save energy technologies work when they were loaded. And 2 kernel consume more energy (and within more rate) then 1.

Unmanaged mode time when RAM is max loaded

RAM consumes less energy than processor but if it is loaded completely a laptop will operate 30-35 % less. What is loaded processor and RAM? In addition to the described processes it will be browser (if you open and close pages with hard layout or a large amount of pictures), frequent opening and closing big documents, even watching films and listening music.

Unmanaged mode time when video card is max loaded

The video card loading with the purpose to hasten 3-D graphic will lead to the very essential energy consumption. Don't forget that during this processor and RAM are loaded almost always. Games and other 3-D applications ??У is a good way to load the computer and to discharge the accumulator in the laptop.

The results were almost the same as with the processor. Again Acer Aspire 5315 is the more saving then others. But it flabby built in video card obviously consumed less energy then processor. It is necessary to interpret the results in two ways. Integrated graphic consumes less energy but processor during this situation consumes more (if we deal with 3-d application).

Discrete video card will consume more but processor will not operate if video card cannot to load all.

The most balanced way to discharge the accumulator. Notice that after graphic test the max energy has Dell Latitude D630 and Toshiba X200 - laptops with big discrete video cards.

Hard Disk and Optical Drive

Because of the boredom during the trip it is possible to start hard disk sorting (removing a big amount of files from one directory to another).

The time of the unmanaged mode of the mobile computer when HDD is maximum loaded

The time of the unmanaged mode will reduce at 20-25 %, but for this you should to copy files between logical disks during 2-3 hours.

The time of the unmanaged mode of the mobile computer when read and save data on DVD

Reading and Saving on DVD will demand more energy than during the same operations with hard disk. Notice, that saving expends a little more time than reading.

The time of the unmanaged mode of the mobile computer when read and save data on CD

More interesting results were for CD. More data flow DVD comes from DVD, more loaded RAM and Hard disk. But operating with CD needs more energy! And reading consumes it more than saving! Why? We suppose it occurs because of speed rotation of the disk. The drive speeds quicker during the operation with CD than with DVD especially when reading. So it is more saving and effective to use DVD. It'll be interesting to know results for Blue-ray. But it is difficult to do because of low popularity of this format.

Network interfaces and USB

We suppose sitting in a cafe in an airport or on the many of us think about energy consumption of Wi-Fi. But when we copy data from flesh card we don't think about it at all. But it is unjustified.

The time of the unmanaged mode of the mobile computer when min Wi-Fi loaded

If you sit with turn on Wi-Fi it practically does not consume energy. If you use Internet during it the results change a few ??У data flow will be low.

The time of the unmanaged mode of the mobile computer when max Wi-Fi loaded

And if you will start to copy a film from one laptop to another using Wi-Fi the energy won't consume a lot. It's seen from the results.

The time of the unmanaged mode of the mobile computer when max Ethernet loaded

Viewing this diagram it is possible to think that Ethernet needs more energy for operation. No, it does not at all. We explain these results with more serious loading of the hard disk. When we tested Wi-Fi, the speed of data copying was not more 20-22 Mbit/sec (connection was set through the 802.11g standard). And with the Ethernet the speed was 80-85 Mbit/sec. It is necessary to think that Wi-Fi 802.11n standard is able to discharge the accumulator quicker than the previous releases of Wi-Fi standard. In our article "Unwinding Home net Wi-Fi" we've tested it speed and it was higher.

The time of the unmanaged mode of the mobile computer when max USB loaded

USB is not the most saving interface. Constant copying from flash card to the hard disk and back to front is able to reduce the operation from 30 to 80 minutes. It is too considerable for such a insignificant operation.


Here we'll try to answer: Is there is any use to listen loud music and watch films.

The time of the unmanaged mode of the mobile computer when sound is turned off and music is reproduced

Notice that so simple operation as music reproduction needs energy consumption but a little.

The time of the unmanaged mode of the mobile computer when music is reproduced throght laptop speakers and headphones

The time of the unmanaged mode of the mobile computer when sound is turned on through the acoustic system or through the headphones and music is reproduced.

Headphones don't consume a lot of energy as it was supposed. But built in acoustic system consumes more energy. And if you like listen music or to watch films from laptop you need to buy headphones.


So now let's see how is it possible to save more energy when laptop operates with accumulator? Not to turn it on! But in some time the accumulator will discharge, but it will very slowly...

But if seriously, it is possible to recommend minimizing the display brightness. The sound influences the energy consumption a little, but it is better to use headphones. Switched on but used rarely, for example for Internet, Wi-Fi doesn't consume a lot of energy. But a browser with a lot of pages and pictures will increase the consumption.

Operations with optical drive are forbidden. Do you like to watch a film? Copy it to hard disk and watch it from that directory. You save more energy. But it was pleasant to see that saving to disk or from disk consumes almost the same amount of energy as reading. And it is interesting that DVD usage saves more energy than CD usage.

To play games is not recommended if you want to save the accumulator charge. The accumulator will discharge for some tens of minutes. Also USB usage is not the best way to save the energy. Don't forget that energy for the device is supplied with USB and these are precious minutes.

We believe all information in this article will be useful for you. You need not to follow the advices surely but for it foundation it is possible to build the best strategy to save laptop energy in special situation.

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Kelly#10 0
Yep! I find what you're saying to be true, at least in the mjtroiay of cases. Considering the years of research and developement, not to mention huge wads of cash, gone into developing both the hardware and the code to control it, some things are better left in-house. And I serioulsly doubt that your coffe would taste any better should your microwave oven run Linux. Nevertheless the call for free code has never been louder than it is today, arguably voices were louder in the sixties, but that was for free love / drugs / whatever, they did not care about code back then, that was military stuff. And, yes, the free code has not only a niche to fill but also a market, these are though largely concerned with exstensions to available technology. How about interfacing your server farm to a display system? Your RAID array to your printer? Hell, how about connecting your toaster to the coffee machine, and the fridge, and to your alarm clock for a timed, ready to eat brekfast?The point is that there is great benefit to be found in leaving your options open, now this may not necessarily mean open code but at least developing coherent standards. Cue the magic teenagers. As long as they have handles to grab they may yet be able to have your breakfast ready the minute you're human enough get out of bed, but leaving your code open is like telleing the world Hey! Put me out of business will ya! .No seriously, I believe that the call for open code for systems, best developed in-house with complete documentation of the involved technologies is a cry from a generation with hubris, not to mention used to getting the way they want whenever they want it . Bloody communists , some may say. Well, I'm inclined to agree. If you find the technology to be inferior you'd be better off calling in some hardware professionals (if you're not one of those as well), develop the product, insert your own code, and pretty soon you'll be running to the patent office and fighting neverending court battles to retain your livelihood. You see, now you're like that corporation you wanted to open their code for you, and you're afraid of competitors buying some other teen's knowledge to throw you out of business.Well here's a tip. Let your hobby stay a hobby. If you're confident enough that your solution is better, go into business and prove that it is.And if your proof is good enough I may one day wake up to a set breakfast without having to hire a Polish maid.Oh yeah, I'd probably still be late for work
Randhil#20 0
Could you coseidnr putting your book trailers on teacher tube and some of the other book trailer sites? Most schools block youtube and so we can't use the trailers with the kids or linked to our book blogs.
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