Reducing my electricity usage
July 19, 2008 3:55 AM   Subscribe

How can I make my WinXP PC use less electricity? I'm trying to optimise my desktop PC's use of energy as much as possible. What are some effective ways to do that?

So far I have:
  1. Taken out a superfluous hard drive.
  2. Set it to go into S3 standby rather than S1, at an interval.
  3. Purchased a LCD monitor that uses less than 1W of electricity in standby.
  4. Unplugged the scanner/printer when they aren't in use.
The only other thing I can think of is that the CPU uses a fair bit of electricity. For various reasons, replacing the CPU isn't an option right now, but I have heard of a program for use on laptops that slows down the CPU to save battery life. Can I use this on a desktop PC, and is it worth using?

Also, are there any other things I could do (that don't involve purchasing new hardware, preferably) to help save on energy usage?
posted by Solomon to Computers & Internet (18 answers total) 4 users marked this as a favorite
Apparently an energy efficient PSU like this will help, ensuring the PSU only draws the power it needs to run the computer, instead of running at full blast constantly.
posted by lukeo05 at 4:03 AM on July 19, 2008

Seriously underclocking your processor would save power, but only if you also reduce the voltage level. Additionally, you may be able to reduce the number of fans in your system. Take out any modems or other cards that you aren't using. If you want to get crazy, yanking out memory will save you a couple of watts.

The disadvantage with underclocking and removing memory is that you may have the computer (and all its peripherals) on longer to accomplish the same task. If you are doing photoshop (or maybe even the latest version of office), and it takes you 80 minutes instead of 60 to do something, you might be wiping out your power savings, or even going into the red.
posted by BrotherCaine at 4:40 AM on July 19, 2008

Seconding an efficient PSU (bonus: they tend to be better engineered and quieter too).

For a no-additional-purchases option which won't affect your performance noticeably, undervolting is a way to permanently reduce the amount of power your CPU uses without impacting CPU speed, and as a side effect, it also makes your machine run a little cooler (which will spin up the fans less frequently, which also saves power and makes your machine quieter). You can see reductions around 5-10% of CPU power draw. Aga

The way it works is that each CPU that is produced has a voltage which is guaranteed to provide it with enough power to run at the specified clock speed, but most CPUs also are capable to attaining their specified clock speeds at a somewhat lower voltage, but it is prohibitively expensive for chip manufacturers to test each batch to find out what the minimum stable voltage would be, so they just specify the safe higher voltage. There are utilities which will allow you to test what the minimum stable voltage is for your system and override the default voltage with a lower one. Again, this doesn't reduce chip clock speed at all (although you can combine undervolting and clock speed reduction for bigger power savings). I have done this to my server combined with underclocking a bit, and it allowed me to get its average watt usage down to 49 watts (also: silent).

rmclock is a popular utility for undervolting. There are a few others but I've had best results lately with rmclock. Here is a how-to guide.

If this sounds interesting to you, I would take a couple days and read up on it -- I think the Silent PC Review forums are a good place to start, just search for "undervolting". I would recommend backing everything up and installing a new system with nothing in it for the part of the procedure where you find the minimum voltages, because it involves system freezes (when you find a voltage which is too low for stable operation) and that is less disturbing when you don't have any important data involved in disk reads or writes when it happens.

Very satisfying if you get it working, since it's basically a free energy savings and it's a pretty interesting geeky project if you like that kind of thing.
posted by Your Time Machine Sucks at 4:44 AM on July 19, 2008

-Aga. Hot CPUs had me thinking about cookers?
posted by Your Time Machine Sucks at 4:45 AM on July 19, 2008

Put everything on a switched power bar, hibernate the computer when you're not using it, and turn the lot off at the switch. That way, you've killed all your standby phantom loads.
posted by scruss at 4:49 AM on July 19, 2008

Switch to an all-black desktop background, and turn off all unnecessary services (and animations, startup programs, etc.). (I'm not an engineer, but it seems logical that these kinds of steps will reduce electricity consumption by a tiny but nonzero amount.)
posted by box at 6:10 AM on July 19, 2008

I thought black used more power than white on LCDs. CRTs save power with black though.
posted by BrotherCaine at 6:22 AM on July 19, 2008

Get yourself one of these. When your PC shuts down (or goes into hibernation), this device will automatically shut off power to your scanner/printer/monitor/external drives/etc. It'll save you having to remember to switch everything off individually.

There's also a version that will cut power to your satellite/dvd/games console/amp etc. when your TV goes into standby.
posted by le morte de bea arthur at 7:14 AM on July 19, 2008

Yeah, why not just hibernate the thing and use zero energy? I think the laws of diminishing returns is kicking in here. You've done a lot already and hibernation is the next step. A minor underclock will results in few saved watts but much, much slower performance. I dont think its worth it.
posted by damn dirty ape at 8:15 AM on July 19, 2008

FWIW, laptops can do this trick because they use speedstep to dynamically slow down the CPU, but desktops also use whats called the HLT instruction to slow down the CPU when its not in use. So the idea that its burning 40 watts 24/7 is simply wrong.

Regardless, I suggest you spring for a kill-o-watt to see your actual use and to measure the results of some of the more voodoo suggestions like changing background color.
posted by damn dirty ape at 8:22 AM on July 19, 2008

Undervolting doesn't reduce the clock speed of your CPU, and it saves power while you're actually using the machine. Still might be too much of a PITA, but I wanted to correct the impression that you can't save watts on a running CPU without trading performance. On two different machines, I was able to reduce voltage on the top CPU clock rate by about 7-8%, as well as increase the minimum power-saving clock rate drastically without it having any effect on energy consumption.
posted by Your Time Machine Sucks at 8:24 AM on July 19, 2008 [1 favorite]

I have a kill-o-watt and it's burning 49 watts 24/7. It's an AMD desktop chip with stepping (but the name of the specific technology is eluding me at the moment).
posted by Your Time Machine Sucks at 8:25 AM on July 19, 2008

Ah, sorry, your 40 watt statement was directed at the OP, apologies.
posted by Your Time Machine Sucks at 8:26 AM on July 19, 2008

I use one of these not only for my computer but also all around the house.
With my computer on "standby" my computer, LCD screen and UPS still use 24 watts; on "normal" use it jumps to 162 watts.
I also have a switched power strip which the printers, speakers etc. all plug in to.
posted by lungtaworld at 8:35 AM on July 19, 2008

It's using the killawatt that set me on the track of reducing the usage. My old monitor would use 12w even while it was turned off, which is why I changed it to the new one.

The base unit uses ~150w on startup, then settles down to about 90-100w. Removing the additional hard drive cuts out about 15w, but it's still using more than I'd like.
posted by Solomon at 9:14 AM on July 19, 2008

In my experience, the standby modes don't work as well as I'd like them to.

Set the computer to enable hibernation. Then change the "when I push the power button on my computer" option to hibernate. When you're done using your computer, hit the button and walk away. It will hibernate- which is a "mode" where it save the contents of the memory to disk and powers completely off. When you turn it back on, it puts that information back into memory and within a few seconds, you're back in action- everything is exactly the way it was when you left, and you used no power in the interim.

You can further "automate" this by getting one of those magic power strips linked above that shuts everything else down when the computer is off. Or, go into the BIOS of the computer and change the "power loss" or "AC recovery" mode to on. When you turn the power switch back on, the computer automatically starts.
posted by gjc at 9:19 AM on July 19, 2008

You've aleady done a pretty good job. Put your PC into sleep mode when you get up. Think about the other power in the room. If you're currently using an incandescent bulb, switching to a Compact Fluorescent will save more power than anything you could do to your PC.

The other option is to buy a laptop. I'm not 100% sure of the power requirements of newer laptops (40-50 watts?), but older laptops use as little as 30 watts of electricity while running. They also tend to have more reliable power management than desktops. Using a laptop would cut your power usage by 1/2 to 2/3.
posted by cnc at 6:15 PM on July 19, 2008

Replace the power supply with a 80 Plus certified power supply. These run at a higher efficiency, meaning that less electricity is wasted as heat.
posted by kenliu at 12:02 PM on July 27, 2008 [1 favorite]

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