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Saving Electricity
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Saving Electricity |
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A typical desktop computer uses about 65 to 250 watts. To find the figure for your particular computer you can contact the manufacturer (not me), or see my section on measuring electrical use. With most devices you can look at the label to see how much energy they use, but that doesn't work so well with computers because the label gives the theoretical maximum, not the typical amount used. A computer whose label or power supply says 300 watts might only use about 70 watts when it's actually running, and only 100 even in peak times with serious number-crunching and all the drives spinning. As long as your computer goes into sleep/standby when you're not using it, your computer doesn't use squat for electricity, compared to the rest of your household. You'll save a lot more energy by addressing your heating, cooling, and lighting use rather than obsessing over your computer. For most people, their computers' energy use is not a significant portion of their total use, even if they use their computers a lot. Of course, you should absolutely make sure your computer is set to sleep automatically when you're not using it, because it's silly to waste energy, but your computer likely isn't even close to being the biggest energy-waster in your home. How much it costs to run your computerTo calculate your costs use this formula:
For example, let's say you have a big high-end computer with a gaming-level graphics card and an old CRT monitor, and you leave them on 24/7. That's about 330 watts x 24 hours x 365 days/yr = 2,890,800 watt-hours, or 2891 kilowatt-hours. If you're paying $0.14 per kWh, you're paying $405 a year to run your computer. Let's try a different example: You have a computer that's less of an energy hog, like in iMac G5 20", which uses about 105 watts, and you're smart enough to turn it off when you're not using it. You use it for two hours a day, five days a week. That's ten hours a week, or 520 hours a year. So your 105 watts times 520 hours = 54,600 watt-hours. Divide by 1000 and you have 55 kilowatt-hours (kWh). If you're paying 10¢ per kilowatt-hour, then you're paying $5.50 a year to run your computer. That's quite a range, $5.50 to $405 a year. It really depends on what kind of computer it is, and how much you use it -- and especially whether you sleep it when you're not using it. Both the examples above are extremes. I used to have only one example somewhere in the middle but then I'd see people on blogs and messageboards misquoting it by writing, "Mr. Electricity says a computer costs about about $150/yr. to run" No, that is not what I said. I said that was just an example. Your situation is almost certainly different, and you need to consider all the variables, like what kind of computer it is, how much you use it, and most especially whether you leave it running all the time or sleep it when you're not using it.
Factors that affect energy use
Add another 35 watts for an LCD monitor, or 80 watts if you have an old-school CRT. Don't forget related devices. My cable modem uses 7 watts, my D-Link DI-604 router uses 4.5 watts, and my Motorola phone box for use with Vonage uses 2 watts while idle (3 when I'm on the phone). Laptop computers use about 15-45 watts, far less than desktops.
Sleep & ScreensaversWhen your computer sleeps (aka "standby", "hibernate") the computer uses 0-6 watts. (So does the monitor.) You can set your computer to sleep automatically after a certain amount of idle time. Setting your computer to auto-sleep is the best and easiest way to save on computer energy use! Here's how to do it:
It's not terribly important to understand the difference between Sleep, Standby, and Hibernate. In a nutshell, hibernate saves your workspace (all the open windows) and then turns your computer off, so it saves more energy than standby, but a hibernating computer takes longer to wake up. For the curious I have a separate article about the differences between Sleep, Standby, and Hibernate. A screensaver that shows any image on the screen doesn't save any energy at all -- you save energy only if the monitor goes dark by going to sleep. If you turn the monitor off at the switch it will use 0 to 10 watts. (Some electronics equipment draws a small amount of energy even when it's switched off.)
Specific ModelsMacs have generally used less energy than PC's, though I haven't tested any Macs since Apple made the switch to Intel processors. If any Mac users would like to send me their readings, tested with a watt-hour meter, I'll be happy to publish the numbers here. Below is how much energy Dell computers use, according to their website in 2006, and how much my Apple iMac G5 uses based on my measurements. I would have included some HP desktops in the table but HP hasn't bothered to update its website with the energy consumption for current models in over four years. For Dell models not listed below try a Google search using this format: site:dell.com b110 watts Replace the "b110" with the model you're searching for, of course. Don't write to me to ask me how much your particular computer uses, because I didn't make your computer and unlike you, I don't have access to it. Contact the manufacturer or buy a watt-hour meter.
Yes, it doesn't make sense that the GX620 is listed as using more power when it's off than when it's sleeping, but I'm just reprinting the numbers from Dell's specs. The University of Pennsylvania has a somewhat more recent list of Mac / PC wattage.
You won't wear your computer out any faster by cycling it once a day, or even a few times a day. Modern computers just aren't that fragile. I did hardware troubleshooting at Apple, by the way. If you don't believe me, maybe you'll believe Jonathan Koomey, a project scientist at the Lawrence Berkeley National Laboratory, who says, "PCs are not hurt by turning them on and off a few times a day." (Wall St. Journal) The useful life of a computer these days is only a few years anyway. The computer will become obsolete long before you wear it out, no matter how often you cycle it. Bottom line: Turn your computer off when you're done with it (or simply Sleep it), and don't worry about it. (more on this topic...) It also doesn't take more energy to start a computer than to keep it running. The only extra energy it takes to start a computer is the two minutes or so it takes to start up, which is barely different than any other two minutes' of use. You'll always save energy by turning your computer off when you're not using it. Of course you don't have to turn it off since you can easily use the sleep or standby mode instead. The myth of "turning it off uses more energy than keeping it on all the time" exists for just about every device that exists, and it's wrong in every single case, in practical terms. (Meaning, you will never, ever, ever see any savings on your electrical bill by keeping something on all the time vs. turning it off. Period.) You will always save electricity by turning your device off when you're not using it (or sleeping it, if it's a computer).
Whether to use a laptop to save energySome people think it's a bad idea to replace desktops with laptops even though they use less energy, because they're more likely to require repair, those repairs are more expensive than desktop repairs, many users thus choose to replace their broken laptop rather than getting it fixed, and laptops require disposal of chemically-laden batteries when they wear out. While these things are true, I think the average person (and the environment) will still come out ahead over all by using a laptop over a desktop, because only a fraction of laptops will actually break and get replaced. If every laptop failed like this during its life (or even if most of them did), we could easily say that it would be better to stick with desktops. But since only a fraction of laptops fail, I still think there's a net savings by using laptops.
Energy-Efficient PC'sIn June 2007 the EPA started giving an "Energy Star" rating to energy-efficient computers. While this is important, sleeping your computer when you're not using it is more important. An inefficient computer that sleeps when you're not using it uses far less energy than an Energy Star computer you keep running 24/7. This is so important I'm going to repeat it: Making sure you sleep your computer when you're not using it is way more important than what kind of computer you use. Computer power supplies are only 55-80% efficient. That means with a cheap power supply, nearly half the energy consumed is wasted. At least 80% efficient power supplies are required to get the EPA Energy Star label, but even then up to 20% of the energy consumed is wasted. (Tom's Hardware) There are a handful of ultra-low-energy PC's available. They all come with some flavor of Linux instead of Windows, and typically come with Firefox for web browsing and Open Office for productivity. The low-power processors they use also mean that they're a bit slow. (e.g., The Linutop 2's AMD LX processor runs at 500 Mhz.)
My recommendations
The Internet and Electricity The Internet doesn't use as much electricity as you might thinkComputers account for only a fraction of worldwide electrical use, even with the burgeoning Internet. Air conditioning, lighting, and refrigeration account for a lot more. The myth that computers are exploding the demand for electricity was given wings by an article in Forbes, which was debunked here. In fact, as inefficient CRT monitors are being phased out in favor of newer LCD screens, and as more peoeple replace their desktop with laptops, computer energy use is likely to remain flat or even go down over the next several years. If you had to have a separate computer to host each website, then we'd have a big energy problem, but fortunately that's not how it works. A single computer (server) can host hundreds or even thousands of websites. In fact, that's what made websites affordable to the masses in the late 90's. If you had to rent the whole computer from your host then the cost would be astronomical. But your site is on the same server with lots of other folks' sites, which is why they call it shared hosting. By contrast, dedicated hosting is when you rent an entire server for yourself. But even then, you can put dozens or hundreds of sites on your server, as I've done with mine. Also, I chose a host that purchases carbon offsets to offset the pollution caused by generating the electric to run the server, which is why you see the "This site is green" logo on the bottom of the page. The very largest sites (Google, Yahoo, eBay) require multiple servers just to run their one site. But those sites are used by millions of people every day. The energy use on a per-person basis isn't that great. Also, the largest companies have been taking bold steps to reduce their energy footprint. For example, in 2007 Google built a massive 1.6-megawatt solar system at its headquarters in California. It generates 30% of Google's peak demand, and around two million kWH a year. It's the largest corporate solar install in the U.S. (There are larger installations at utility companies, but this is the biggest for a company generating its own electric. Google has a page where you can see how much electricity they generated in the last 24 hours and the last 7 days. You can also see a flyover video of their installation. The system will take 7 years to pay for itself, and then will generate free electricity for another 18. (The lifespan of the panels is about 25 years.) It doesn't end with this huge installation. In late 2007 Google announced its plans to develop a whopping one gigawatt of energy from renewable sources at a cost cheaper than coal, and to do it "within years, not decades". Wow.! Yahoo is also addressing its energy footprint. They have a very progressive Commute Alternatives Program to encourage employees to not drive to work alone. It includes things like shuttles to transit stations, transit discounts, a carpool matching service, preferred parking for carpoolers, bike racks/lockers/showers, and free lunches, massages, and movie tickets to employees who participate in the program. Questions & AnswersSee questions I've received and answered about how much energy computers use. Please note that I'm not accepting any more questions for this website, period. Last update: June 2008
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 All advice is given in good faith. We're not responsible for any errors or omissions. Electricity can kill you; if you're not competent to work on your electrical wiring then hire a professional to do it. |
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