How green is your PC?

How green is your PC?

Summary: How much does it cost to run a PC or a Windows Home Server 24/7? I've just completed a abttery of power management tests in my office, and the numbers surprised me. In my neighborhood, running a home server costs about $5 a month in electricity, but I can cut that bill by two-thirds just by using the default power management settings in Windows Vista.


In my review of HP's MediaSmart Server a few weeks back, some commenters asked how much power this always-on server uses. I promised to do some testing, which is now complete. In the process, I tested a desktop PC and learned a few things about Windows power management that I didn't know before.

To measure power consumption, I used a device called a Kill A Watt Electricity Usage Monitor, which is about the size of a standard plug-in surge protector. (I picked up a pair for under $25 each from a mail-order supply house. Amazon has them for $21 each currently.) You plug the gadget to be tested into the Kill A Watt socket and then plug the box into the wall socket. The front panel shows voltage, line frequency, power factor, and cumulative kilowatt-hour usage for that device.

The MediaSmart Server I tested contained a full complement of four internal SATA hard drives. Over an 18-day period, the server used a total of 31.3 kWh, for an average power consumption of 72.5 watts.

My home-built Windows Home Server box, a Dell E521 with two internal SATA drives and one external drive connected via eSATA cable, used 39.7 kWh over the same period, which works out to 91.9 watts on average. or about 26.7% more than the HP server. (This calculation includes the power consumed by the external drive's power supply but not by the monitor attached to the server, which is off except for rare maintenance operations.) If I added a second external drive to match the configuration of the HP server, this value would probably go up slightly.

My electric company charges $0.0788 per kWh. That means the MediaSmart server costs me $4.17 per month to run. Over the course of a year, that means I save about $13.39 by using the smaller, more energy-efficient device rather than building my own. And even though this is an always-on device, I think that Microsoft could probably do more to conserve power in Windows Home Server, and I hope they'll do exactly that in the next upgrade.

I also attached a Kill A Watt meter to the Dell C521 PC that I've been using for my ongoing Media Center experiments. At rest, it uses about 64 watts, and its power consumption is roughly equivalent to the HP server over time. However, it's dramatically more power-efficient, thanks to Windows Vista's sleep mode. In the past 24 hours, it has used less than 0.5 kWh. Over the course of a month, that's about $1.20 in electricity. The secret of its power-saving success is S3 sleep mode. When this system kicks into S3 mode, it uses a mere 3 watts, according to the Kill A Watt device. That 0.5 kWh equals 8 hours a day of full-power usage, coupled with 16 hours in sleep mode. If I were to leave it on with sleep disabled, energy usage would triple. Using the default Balanced power settings for the three PCs in this house will save more than 1000 kWh over the course of a year, or $82.

After taking these measurements, I'm sold on the benefits of using sleep mode in Windows Vista. I'll explain how to fine-tune power settings (and how to avoid one big gotcha) in my next post.

Topics: CXO, Amazon, Hardware, Hewlett-Packard, Operating Systems, Servers, Software, Storage, Windows

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  • What is the difference ....

    What are the differences in the sleep/standby/suspend modes between
    Vista and XP?
  • RE: How green is your PC?

    I recently built my own Windows home server and I also used the Kill A Watt to measure the power it used. I was very happy to see that it only used 60 watts. This is the same power that a light bulb uses. I am satisfied with that.

    I also reviewed the software for Windows Home server
  • Cost of Power

    If you live in a PGE area like California, electricity is FAR more expensive. I pay $0.44 cents per KWH for the last usage (and nearly $0.12 for the first. If I shaved off power, it would come off the last KWH price, not the first so that's what matters to me.

    7 cents a KWH!! PGE should be regulated by those they don't bribe.
    • You won't like this...

      In Chelan County, this is what we pay:

      First 1,000 kWh ? 2.18 cents
      1001 to 2000 kWh ? 2.70 cents
      Over 2000 kWh ? 2.85 cents

      Of course, I live less than 1/2 mile from the mighty Columbia river, and Rocky Reach Dam is about 5 miles upstream, and Rock Island Dam is about 7 miles downstream, so it sort of goes with the territory. There is an Alcoa aluminum plant right next to Rock Island Dam, and they basically get their power free, in return for locating here--and they use 25 percent of the output of both dams! Serios power-hog there!
  • I don't care

    Green is easy.

    For example, when I change the oil in my old big gas guzzling
    truck, I just go back into the woods and pour the oil into the
    ground. After all, that's where it came from, right?

    Gheesh, can't be any easier then that.
    • I agree - and what about this:

      people at my work complain that I am printing too much paper - "that's bad for the environment". What BS. I reply that nothing burns better than paper, and that trees have a habit to grow if you plant a seed. That makes them angry haha.

      But what gets them REAL angry is when I ask if they have children. They say yes. Then I say that THEY are BY FAR the bigger polluters because each child in his lifetime
      - generates thousands of kilos of waste
      - burns through about 3 to 5 cars (with all that goes with it)
      - uses massive amounts of detergents, washing stuff etc.
      etc. you get the picture.

      Well, I don't have kids so just shut up. Then they EXPLODE because it hits home that they're wrong and I'm right.

      Yep, that's what you get when you make yourself a "God" called "earth" and proclaim an Accuse-All-Fest for not being 'green' enough.

      Now, where do I leave this used oil... oh - there's a nice place...
      • Wow

        You sound like you argue about things like this a lot. Must be fun to be your friend or to work with you.
        • Thanks

          We have a lot of fun. It's only the militant 'Know-Betters' that don't like hearing these kinds of facts. Try it some day.
      • Whoa! I love your way of thinking

        Reminds me of this young guy that used to work for me. He said the machine he was running was too loud and it was damaging his hearing, so I told him he should just turn the radio up louder so he couldn't hear the machine.

        Problem solved!
  • OK Ed,

    how's your house heated? Did you figure out the differences between the costs based on excess heat generated by the system(s) and heating the house otherwise? Yep, in the summer your cooling system will work harder.
    • Non issue here

      Radiant heat in the floors, swamp cooler in the summer time. I save money in my office in the winter and spend pennies in the summer, using the cooler for a max of about two or three weeks.

      Others might have a different situation, but the climate here plus layout of my house and office work well.
      Ed Bott
  • RE: How green is your PC?

    A 24/7 server should be ultra low power....... Check out Tranquils systems - here

    these babies run from 24W upwards !!
    • Claims versus reality

      I'll want to test these before I believe that 24W claim. Especially if it's fully loaded with multiple drives. Can't buy them in the US yet, so if someone can pass along independent test results I'll report them.
      Ed Bott
  • Quiet, Effecient Server

    I do have one hard drive in my server, which my server is home-automation-based when it comes to controlling lights and appliances.

    I might plan to buy an energy-effecient hard drive -- maybe either a 500GB or 1TB (for expanding my hard disk space).
    Grayson Peddie
  • My PC isn't green and I reject accusations.

    "Green" is a new religion, a fad that will go away. People are so ignorant - each generation chooses their own "issue" or worthy goal, and it really doesn't matter in the big scheme of things.
    • Feeling guilty?

      What "accusations" are you rejecting? This article was about reducing electricity usage and thus cutting the amount of money you pay to run a PC. There was no political content in it and not even a hint of environmentalism. And yet you see an "accusation?"

      Touchy, touchy, touchy...
      Ed Bott
      • Oh Ed...

        Your blog didn't contain any accusations so it should have been clear to you that I was referring to the broader context. You're touchy these days! Didn't like what I wrote? Too bad Ed.
        • Poster is correct

          It is clear that the poster's use of the word "accusations" refers to the broader context of the article. It is also clear that the author of the article has an environmentalist agenda. It is indeed the fad of the '00s.
          • Dude, you've ODed on tinfoil

            "It is also clear that the author of the article has an environmentalist agenda."

            Or perhaps, just perhaps, the author of the article is interested in saving money on his electric bill every month.

            Given that energy prices are increasing at an average rate of 12% per year, this might seem like a sensible thing for anyone to be interested in.
            Ed Bott
          • Ok save

            a few pennies. It thinh I worry about my home (oil comsumption) and car (gas mileage) before my PC, which isn't that important to me.
            Did you check to see how much swithing from regular bulb to energy efficient lights would save you? it's more than one PC I bet....
            I agree Ed saving money is important, but go after the big money wastes first.... Then worry bout a few bucks.