thank you. that helped a lot 
An interesting article - thanks for the effort Jeff
Thanks for the info. my laptop battery runs down to 1 volt while ac adapter is connected. WHY? THE DELL xpI. P150. TWO ICONS FOR BATTERY STAY LIT.
Does anyone know how much power a laptop consumes (typicaly) when it is plugged in and not charging versus when it is plugged in and charging the batt?
Nice article.
Has anybody done a comparison to see how much laptop screen size affects the power consumption.
Iām asking because I have a 17" Dell M1705, and am wondering if I wonāt be able to use it on the plane running of an EmPower plug.
Applications spend the majority of their time waiting for user actions, and the OS knows that it can put the CPU into a low power mode. Properly written programs yield as much as possible. Poorly written games run in a tight update/paint cycle, which keeps the CPU at full utilization. The shortened battery life is obvious.
āPoorly written gamesā, a few of which Iāve developed, arenāt sitting around waiting for user input most of the time. Theyāre simulating the game world.
I would love actually to do Kill-a-watt tests, but unfortunately I donāt think this device is sold for 220V power systems ā¦
As a rough idea, can we assume that approximately twice the screen area would consume twice the power, or is it non-linear?
Even tough power consumption of an optical drive was not tested, the HD numbers seem to belie my theory that you could reduce the battery impact of watching a DVD movie on a laptop if you could buffer chunks of the video into RAM (like a RAM disk, I suppose) and let the DVD drive spin down in the interim. Iād think a DVD drive would draw even more juice that a hard drive.
this is a good research.anyone has done similiar researches?
anyway iāve googled and found this - http://www.girr.org/mac_stuff/laptop_power.html
this guy is testing over his APPLE,and Jeff,i would think that maybe u would like to include the readings during Boot,Log-in and Shut down?
because from the link iāve just pasted,it shows that the booting and logging consumpts a different wattage,iām not too sure if itās same as defragmenting but i do think that it worth a test.
looking forward to see the tests by you or others. 
Its odd that laptops would fail on constant use. Iāve seen a number of reports that suggest that its the start up and shutdown that causes the most damage to drives. Even the vauge google hdd survey suggested that things like operating temperature
Interesting experiment, I did the same thing to me circa-2007 Dell notebook: http://vostro.homeip.net/page?benchmarks
Half brightness, general office/internet use: 16W
This is the power consumption you can expect if you are just typing up your TPS report while browsing wikipedia.
Minimum brightness, idle, hdd on, wifi on: 11W
Half brightness, idle, hdd on, wifi on: 13w
Max brightness, idle, hdd on, wifi on: 15w
Screen off, idle, hdd on, wifi on: 9w
The difference between max and min LCD brightness is 4 watts. Turning of the screen completely saves an additional 2 watts.
Half brightness, wifi on: 13w
Half brightness, wifi off: 12w
Turning off wifi completely saves 1 watt
Half brightness, speedstep on idle: 13w
Half brightness, no speedstep idle: 15w
SpeedStep/PowerNow! definitely saves a measurable amount of electricity (2 watts)
half brightness, 1 core fully loaded: 28W
half brightness, 2 core fully loaded: 36w
Compare to idle, running 1 CPU core at 100% consumes an additional 15 watts, and two core together will cost you a total of 23 watts of additional power.
PowerPlay Max Performance(idle): 14w
PowerPlay Max Battery(idle): 13w
PowerPlay Max Performance(gaming): 36w
PowerPlay Max Battery(gaming): 32w
I used Flatout 2 as the game in this test. Naturally, gaming is one of the quickest way to drain your battery.
No disk usage: 14w
Heavy Disk usage: 17w
Constant Disk IO (with lots random seeking) draws about 3 watts of energy.
1700mhz, default voltage: 15w
800mhz, default voltage: 14w
800mhz, 0.85volt: 12w
800mhz 1 core fully loaded: 17W
800mhz 2 core fully loaded: 19w
Underclocking! By underclocking the CPU manually to 800 Mhz, I lowered the power requirement by almost 15 watts.
[sorry about the long post]
If everyone used ULV CPUs (Ultra Low Voltage) CPUs from Intel - compared to normal CPUs then we would save 70 watt since ULVās only consume 5 wattā¦If you use aircondition then you need another 2 watt to remove 1 watt heatā¦so, saving 70 watt would actually save 210 watt Now multiply that by 100 million computers worldwideā¦thatās a whopping 21 billion watt that could be savedā¦
It is quite sad that only super expensive Sony notebooks (Maybe also a couple of other brands, too) is being sold with the ULV version. The ULV CPU is up to 80% less consuming than even the mobile CPUās (that are rated 27 watt - for centrino).
Thanks for doing this! I recently noticed my laptop losing about 30% battery power per day it was in āsleepā mode. That seemed rather like a lot, unfortunately it was still too small a draw to register on my kill-a-watt meter. I use the sleep mode very sparingly now.
The person defending āpoorly written gamesā is exaggerating the situation. It is not spending most of the time simulating the game world. Most games are poorly written in terms of power usage, in that they will use all spare CPU while in menus, while paused, whatever, because itās easy to make the game loop ādraw screen, check input, run world, repeatā, much easier than it is to put in āif nothing is happening wait until something isā. For full-screen games I know many will use ~100% CPU while paused and unfocussed (ie. the screen of the game is not visible, the world is not changing, there is no justification for the loop still looping other than it being easier to write).
I also write poorly written games, but I donāt defend the practice as reasonable. Iām just lazy. My one concession to power (because I program on a laptop and donāt like it to get leg-burning hot) is to have a (default) option to cap the framerate (at 60fps) using calculated āsleepā cycles. Also to not draw the screen when it isnāt visible anyway. Itās not as good as proper waiting for a message, but this way āgame is paused, screen is hiddenā translates to about 1000 instructions per second (āis there input? Do I need to draw the screen? How long to sleep? Sleep. Repeat * 60.ā), or less than 0.1% CPU usage. Itās still poorly written, but it doesnāt try to set fire to my legs. Bioshock, The Witcher, and basically every other modern game Iāve tried will, when minimised, still use 99% CPU.
Just wanted to say that I was trying to Google for laptop power consumption in sleep mode and this was the first actually useful link I found. Plus I clicked through to the main page and I have a new bookmark. Thanks!
Would like someone to test an internal CDRom drive for power consumption. I want to run linux LiveCD on my laptop while driving and without a harddrive present. Is a CD drive as bad as I expect power wise?
Lloyd, some livecds include an option to load the whole cd into memory on boot. This would reduce the consumption of power after loading. Knoppix is one such livecd, and it allows pretty good customization options. The boot option to load the entire cd to ram is aptly named ātoramā.
How did you actually determine how much power each component used?
Also, Iāve seen the new Hitachi Travelstar 500GB HDD 5K400, and Hitachi claims it uses 1.9 watts read/write and .7 watts idle. Are your results accurate? Have hard drives come that far in only 5 years, using like, 10% as much power as previous yearsā hard drives?
And in the cases of (these) hard drives, power consumption on idle vs sleep makes virtually no difference (I was real bored so I decided to figure out how much battery we actually save). On a 63 Wh battery (226800 joules), a hard drive mentioned in this article using 14 watts sleep 15 watts idle, uses 23.1% and 24.6% of the batteryās total energy (respectively) if we use an average of about 65 watts. This means that of the 226800 joules available, we can set aside 52390.8 joules if left completely asleep, and 55792.8 joules if left completely on idle. Thatās a difference of 3402 joules, which means that if put asleep, we could (knowing that one watt means power usage of one joule per second) save aboutā¦53 seconds! Iām 99% sure I did my math right, but anyone who knows their physics/math, please feel free to correct me (and please only correct me if you genuinely know what youāre doing 
53 seconds is NOTHING!!!
When I have more time, Iāll determine how much power savings there is for EACH component on high/low/asleep/idle etc etc (monitor, wifi, cpu etc).
I realize this is a fairly old post, but I thought Iād point something out. You claim the CPU uses more power than the graphics, but Iām not sure your numbers support that claim.
What youāve actually proven is that the difference between idle and load states for your graphics chip is 3 watts, and the difference for your CPU is 11 watts. Thatās fine, but you canāt claim the CPU uses more; itās entirely possible the CPU is idling at 1 watt and loading to 12, while the graphics chip is idling at 10 watts and loading to 13.
I donāt think itās likely, and I suspect your conclusion is probably correct, but you still canāt claim the graphics chip only uses 3 watts. It certainly uses at least a watt or two at idle.