# PC energy usage **URL:** \ **Category:** Factual Questions\ **Created:** [January 18, 2003, 6:54am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435 "2003-01-18T06:54:48Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![Fuel](https://avatars.discourse-cdn.com/v4/letter/f/df705f/32.png) [@Fuel](https://boards.straightdope.com/u/Fuel)\ **Post date:** [January 18, 2003, 6:54am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/1 "2003-01-18T06:54:48Z")
1. compared to say a 100 watt lightbulb, how much energy does a running Dell PC consume in say an hour (with monitor on)? an estimation is all i am looking for. 2. if i am downloading and playing music and watching a dvd and all kinds of other things, does it use more energy than if the PC was just sitting idle, with disks and monitor on? thanks in advance. ---
**Author:** ![cw](https://avatars.discourse-cdn.com/v4/letter/c/71c47a/32.png) [@cw](https://boards.straightdope.com/u/cw)\ **Post date:** [January 18, 2003, 7:03am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/2 "2003-01-18T07:03:00Z")
I think that it would vary greatly depending on your PC’s configuration and periphrials. I found something that said between 50 and 100 watts an hour average from this site [http://www.wyse.com/overview/energy/](http://www.wyse.com/overview/energy/) ---
**Author:** ![Zagadka](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zagadka/32/7272_2.png) [@Zagadka](https://boards.straightdope.com/u/Zagadka)\ **Post date:** [January 18, 2003, 7:51am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/3 "2003-01-18T07:51:51Z")
1. Not enough to make a decent impact unless you are really pushing the system (using a 3d intensive game, for instance), but computers generally spin down the drives and turn off the monitor when idle. ---
**Author:** ![neutron\_star](https://avatars.discourse-cdn.com/v4/letter/n/51bf81/32.png) [@neutron\_star](https://boards.straightdope.com/u/neutron_star)\ **Post date:** [January 18, 2003, 8:53am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/4 "2003-01-18T08:53:19Z")
From [an article on PCWorld.com:](http://www.pcworld.com/resource/article/0,aid,9058,pg,4,00.asp) > [@](#): > > How much power a computer consumes depends on its processor, components, and design and the amount of time it is actively in use. Not uncommonly, a computer designed to handle 200 watts (exclusive of the monitor) draws about 100 watts when in use and 50 when idle. > > The real power hog is the monitor. A 17-inch monitor that’s left on all the time can easily use 160 watts; even a 14-inch model can consume 100. Do the math: At an average cost of 12 cents per kilowatt hour, a 17-inch monitor that never goes to sleep will cost over $150 a year to operate. See our power usage chart for details on other peripherals and their juice consumption. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [January 18, 2003, 10:32am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/5 "2003-01-18T10:32:42Z")
> [@](#): > > \*Originally posted by cw \* > \*\*I think that it would vary greatly depending on your PC’s configuration and periphrials. I found something that said between 50 and 100 watts an hour average from this site [http://www.wyse.com/overview/energy/](http://www.wyse.com/overview/energy/) \*\* watts is the correct unit. Watts an hour is meaningless. ---
**Author:** ![Zagadka](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zagadka/32/7272_2.png) [@Zagadka](https://boards.straightdope.com/u/Zagadka)\ **Post date:** [January 18, 2003, 10:41am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/6 "2003-01-18T10:41:12Z")
Most PC power supplies are around 300 - 400 Watts, but that doesn’t include monitor. ---
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [January 18, 2003, 11:06am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/7 "2003-01-18T11:06:59Z")
Are CRT screens and LED screens comparable in their power consumption? ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [January 18, 2003, 11:24am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/8 "2003-01-18T11:24:09Z")
> [@](#): > > \*Originally posted by Achernar \* > \*\*Are CRT screens and LED screens comparable in their power consumption? \*\* I’ll assume that you meant LCD screens. From [Howstuffworks](http://www.howstuffworks.com/monitor8.htm) > [@](#): > > Power consumption varies greatly with different technologies. CRTs are somewhat power-hungry, at about 110 watts for a typical display, especially when compared to LCDs, which average between 30 and 40 watts. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [January 18, 2003, 11:33am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/9 "2003-01-18T11:33:07Z")
> [@](#): > > \*Originally posted by Zagadka \* > \*\*Most PC power supplies are around 300 - 400 Watts, but that doesn’t include monitor. \*\* A 300 W supply doesn’t necessarily consume 300 W. The rating means that it’s _capable_ of supplying 300 W. If it is actually delivering an _output_ power of 300 W, then it’s consuming an _input_ power from the mains greater than 300 W, probably about 350 W. However, a 300 W supply is also capable of delivering an output of, say, 85 W whilst consuming 100 W. Hence **neutron star** ’s figures above. ---
**Author:** ![cw](https://avatars.discourse-cdn.com/v4/letter/c/71c47a/32.png) [@cw](https://boards.straightdope.com/u/cw)\ **Post date:** [January 18, 2003, 11:35am UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/10 "2003-01-18T11:35:17Z")
> [@](#): > > \*Originally posted by sailor \* > \*\*watts is the correct unit. Watts an hour is meaningless. \*\* Picky, picky. tell that to the author of the website I derived the source from, I never claimed to know the least bit about electricity. All I know is that it’s not the watts that kill you, it’s the amps 🙂 . ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [January 18, 2003, 12:00pm UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/11 "2003-01-18T12:00:57Z")
[aside] Honest-to-God real life conversation I once had with a Bavarian: Him: Rudolf Diesel was much more important historically than that English guy who invented the steam engine. What was his name again? Me: Watt. Him: You know, that guy that invented the steam engine. Me: Watt. Him: You know exactly what I’m talking about, don’t be a smartass. What was the #$%@%'s name? Me: Watt. At this point half of the people around the table were rolling on the floor, and other half were trying to restrain the Bavarian. [/aside] ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [January 18, 2003, 2:29pm UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/12 "2003-01-18T14:29:15Z")
> [@](#): > > \*Originally posted by cw \* > \*\*Picky, picky. tell that to the author of the website I derived the source from, I never claimed to know the least bit about electricity. All I know is that it’s not the watts that kill you, it’s the amps 🙂 . \*\* I don’t know. I feel he has a right to be picky about the _site_, and I don’t think he’s being picky with you _per se_. It irritates people like **sailor** and myself when people who ought to know better (like people making energy-oriented sales pitches) don’t know what they are talking about. You should see how picky I get over coal issues. 🙂 ---
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [January 18, 2003, 4:06pm UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/13 "2003-01-18T16:06:40Z")
> [@](#): > > \*Originally posted by Desmostylus \* > I’ll assume that you meant LCD screens. From [Howstuffworks](http://www.howstuffworks.com/monitor8.htm) Oops! Yes, an unfortunate typo. And thanks! ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [January 18, 2003, 8:03pm UTC](https://boards.straightdope.com/t/pc-energy-usage/149435/14 "2003-01-18T20:03:37Z")
My understanding (which could be wrong, but I was told this by someone who should have known) is that a 300 W power supply _draws_ 300 watts. The usual rule of thumb is that the maximum it can supply is half of what it draws, so it can supply up to 150 W. Of course, if less is consumed, then it draws less. If it weren’t rated by what it draws, you could not add it up with whatever else was on the circuit to see if you have overloaded it. Although in theory, a single circuit (in North America) could supply 1,650 watts, in practice it is good to limit it to 1,500.