Have you ever thought about how much it cost to run your PC -- the one you're using to read this article? What does it cost to play games, surf the Internet, or download files? It all costs money -- money that you, your parents, or whoever is in charge of the monthly electricity will have to pay. Those of you in charge of paying this bill will surely be interested in keeping costs down, which is why you might want to pay a little more attention to what sort of hardware you are using in your computer.

Many users -- especially computer enthusiasts -- put together a new PC that can easily handle any task, without much thought for power efficiency. If you intend to use the computer primarily for gaming, buying a high-end processor and graphics card makes sense. Likewise, if you intend to do complex three animations or movie encoding, you'll probably want to have as much processor power as possible. If all you're going to do is watch movies, run Microsoft Office, and surf the Internet, you're not going to put a big load on any of the components. In that case, your PC will typically be idle and waiting for user input, while any high-power components will still go merrily along sucking down extra power.

We recently looked at the topic of power consumption for each component in the PC. Of course the numbers were merely a rough estimate for our specific setup, programs, and tasks, so that article could serve as a baseline for the amount of power your system might require. We also discussed how power requirements affect the type of power supply that you will want to purchase. In this article, we want to focus more specifically on the costs of running a computer (not counting anything like broken components and upgrades). We look at electricity prices in the US and Europe to calculate how much various types of PCs actually cost to run. Perhaps you're one of those people with multiple systems -- one for gaming, one for office work, maybe one or two for the kids, and perhaps a few extras running distributed computing tasks 24/7. We will look at several different workloads to see how much various types of systems actually end up costing on a hourly, daily, and yearly basis.

KWh prices in the U.S and EU

When we started researching prices of electricity (measured in kilowatts hours/kWh) for the different countries, we were surprised by the huge differences in price. In the US prices range from $0.05 to $0.21, according to the Energy Information Administration -- the average price is $0.089 per kWh. European prices are different for each country, so we will just take Germany as an example. Prices there are high relative to the US but about average for Europe. In 2008, Germany has an average of 17 to 22 Cents (€) -- about $0.22 to $0.29 USD! That's anywhere from 1.5 to 6 times as expensive in the old world depending on where you live; obviously, areas where costs are higher will probably be more interested in PC power consumption, but that is a separate issue from what we are looking at today.

Calculating Power Requirements and Costs
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  • walk2k - Tuesday, November 18, 2008 - link

    If you're curious to find out what your system actually uses, for about you can buy a P3 "Kill-a-Watt" power meter from Amazon for about $24. This is a doo-hicky that plugs into the power outlet, and then you plug whatever you want to measure into that. I've personally found it very enlightening.

    My current PC uses about 120 watts idle in XP, up to about 150 watts when actually doing stuff (cpu slightly loaded, HDD churning). Then in games with the GPU loaded it uses about 200 watts. I only managed to get it to 233 watts when running both a cpu stress test (Orthos) and GPU benchmark (3dmark06) at the same time.

    I'm in CA and pay about 13 cents/Kilowatt/hour so theoretically if I left my system on 24/7 (I don't) at idle it would cost me about $11 per month. In reality I use my computer about 5 hours a day, with about half games (200 watts) and half just surfing, etc (120 watts) so say average 160 watts x 8 hours x $.13 x 30 days = $5 per month.
  • glynor - Tuesday, November 18, 2008 - link

    The prices listed on the EIA website that you used to generate all these numbers (for the US) are based only on the price residential customers pay for energy generation, and do not include the cents per KWH charge that all customers must pay for transmission. Even though I simply take the standard offer from my utility company (like most people), my actual price is roughly DOUBLE what the EIA lists as the average for my state.

    Look at your bill. Make sure to add the totals for both Generation (Supply) and Transmission. These are billed separately.

    With that in mind, most of the example totals reported in this article, and certainly all the comparisons to "Europeans paying more" are completely bogus!
  • Maiyr - Tuesday, November 18, 2008 - link

    Why bother with all of this just to figure out how much it costs to run your system ? Surely someone must have thought of just plugging in a Kill-A-Watt Electricity Usage Monitor....

  • gochichi - Tuesday, November 18, 2008 - link

    I would look for better efficiency rating for the following reasons (in this order):
    1) I speculate the product is a higher quality product.
    2) Inefficiencies turn into waste heat, cooler is more stable, more pleasant, and longer lasting (speculations)
    3) I guess maybe saving a couple of bucks on my bill, but it's definitely not as important to me as just knowing that a have a "pimp" power supply.

    What this article does make me want to do is try to figure out what sleep modes best suit my desktop computers (particularly my seldom used older desktop). Cold booting is inconvenient and I have been careless about finding a reliable sleep mode. I think the trick is to go S1, I just switched my main computer from S3 to S1 and it really helps stability and responsiveness.

    I wonder how running laptops does in terms of power efficiency. There's got to be a ton of inefficiency caused by charging and discharging the batteries all the time. The design circling around a portable battery also makes it pretty power thrifty at the same time. Just curious as to how it actually pans out. Laptops have typically been more robust in sleep mode too though.

    Random comment: Is it just me or have software updates gotten beyond the ridiculous point? Seems like they are not only often, but they are in your face... like it's OK to interrupt what you're up to a few times a week to get the update "right now"... I mean forcefully.

  • bob11d50 - Sunday, November 16, 2008 - link

    I just wanted to justify my purchases of energy efficient computer components.

    The reason for this was about 3 years ago I had 9 people living in my house and the power company was on a teared system. I got up to the fourth tear where power was up to $0.85 KWH. This was in San Jose California with PG&E as the power company.

    I got my server down to 77 WATS with a EE Athlon at idle from about 230 with my dual Opteron. All measurements were using the Kill-A-Watt.

  • sheh - Saturday, November 15, 2008 - link

    I was always under the impression your total power readings were at the outlet, and so included the efficiency loss of the PSU. If that wasn't the case, how do you measure total power draw from within the computer?
  • Christoph Katzer - Sunday, November 16, 2008 - link

    Motherboard, system, graphics-reviews got readings from the wall. power supplies are loaded with a programmable load, so we can easily calculate the losses. You can know the power draw from mobos, gfx and so on when measuring the power distribution inside of the case which isn't difficult if you know which cable powers which part of which component ;)
  • bigsnyder - Saturday, November 15, 2008 - link

    What kind of case is that in the picture?
  • Christoph Katzer - Sunday, November 16, 2008 - link

    Silverstone TJ10
  • GimpyOne - Saturday, November 15, 2008 - link

    Not sure about Europe, but here in the US, the cost of "electricity" is only about half the bill. Once they tack on things like Fuel Cost charges, Energy improvement riders, resource adjustments, etc. you double the actual bill (literally).

    So more appropriate cost saving could actually be closer to 2x what is here.

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