Desktop Energy Savings Guide

by Reads (8,144)

Energy usage is arguably one of the most important factors in running any PC. At the same time, however, it’s also one of the most overlooked. Without sufficient power, components won’t run; without stable power, components get damaged. While manufacturers work ever harder on achieving record new efficiencies in low-end computing, enthusiasts spare no joule in trying to push their equipment to the limits. In either case, consumers rarely take the cost of the energy itself into account.

The desktop isn’t the only thing on your desk that guzzles electricity. Monitors can draw a significant amount of power, especially when you consider the trend toward ever-increasing display sizes. Many manufacturers now ship 30 inch displays, and some users employ even larger HDTV units. With gaming and internet video becoming more popular, a good set of speakers is now an integral part of the multimedia experience. Add in a second monitor, external hard drive, external optical drive, printer, desk lamp and other accessories, and you’ll find the average home office suddenly balloon into an energy expenditure of significant proportions.

Sometimes it isn’t enough to merely turn electronics off. With the introduction of “standby modes”, manufacturers have offered quicker startup times at the cost of electrical efficiency. Power adapters left plugged in while a device is off or not charging will often continue to draw current and let it dissipate uselessly as waste heat. This “vampire power” is estimated to add up to ten percent of the total electrical costs of a home. The International Energy Agency published a free PDF on this phenomenon some years back, cleverly titled “Things that Go Blip in the Night.”

The Kill A Watt
The question now becomes, “how do you figure out how much electricity your devices use?” Enter the Kill A Watt (KAW). The KAW is used to measure how much electricity is consumed by anything that plugs into a standard outlet. The KAW is plugged into an outlet and the gadget is plugged into an outlet on the KAW. The device then measures how much current is being drawn by the gadget. What’s interesting about the Kill A Watt is that it can give an answer in terms of kilowatt-hours (kWh), the nonstandard unit used by utility companies. This makes it easy to quickly calculate how much an item costs to leave running for an hour, day, or even a year.

As a brief example, let’s say that you have four 75W light bulbs lighting up a kitchen.75W * one hour * four light bulbs = 300 Watt-hours, or 0.3 kWh. Assuming that they’re left on for 3 hours a day, those four bulbs will consume 0.9 kWh of electricity.The national average rate for electricity in the United States is 10.4 cents per kWh. This would mean those four light bulbs cost a little over nine cents per day to run, or just less than three dollars each month. When you consider the fact that many people leave one or more computers running twenty-four hours a day, it’s easy to see how costs can add up.

It’s easy to ignore how much electricity is consumed by a device when it’s being used. You watch some television, heat up a pizza in the microwave, charge your cell phone and turn the air conditioner to make things a little cooler. When the bill comes at the end of the month, however, it’s always a surprise. People wonder how they could ever have possibly used that much energy (the U.S. Department of Energy has an easy-to-read graphic that may illuminate some of the confusion here). This is why the Kill A Watt is so useful – it forces you to look at exactly how much electricity a machine uses, and from there, how much it costs you every month. It’s harder to leave something turned on, whether it’s the A/C or PC, when you have a concrete understanding of the associated costs.

The Numbers
To get an idea of the energy costs associated with various computer systems, readings were gathered from several machines. The systems fall along different points of the performance spectrum. This is not intended to be a comprehensive or even highly comparative analysis of computers, merely an example to show real world use. Keep in mind that a computer’s power supply rating, and how much power it uses, are two completely different things. The power supply in the Lenovo S10 is rated for 650W, but it doesn’t come close to using that whole amount.

For the following systems, power use was checked both at idle and when playing a game. All measurements are in Watts. The Lenovo S10 workstation was running Crysis, the Xbox 360 was running GTA: IV and the Playstation 3 was running Uncharted: Drake’s Fortune. In all three instances, the systems were stressed with lots of action sequences and panning.

System Off Idle Gaming
Lenovo S10 1 164 246
Playstation 3 0 122 166
Xbox 360 2 107 138

There are obvious disparities in these numbers, but again, the systems are comprised of wildly different components. While the Lenovo S10 definitely gives the user awe-inspiring amounts of processing power, it definitely draws its share of current at almost twice the wattage of the PS3. Even when idling, the S10 draws over 160W, whereas the Xbox 360 uses a good bit less. If power consumption is a serious concern, and you’re satisfied with the content available on consoles, you might think twice about investing in a heavy-hitting desktop system.

Multimedia/General Computing
More and more these days, the computer is becoming the place to go to experience digital content. High definition media is playing a significant role in this growth. Home Theater PC (HTPC) adoption is also on the rise, and these computers are particularly well-suited for mention in this article as many of these systems are left on 24 hours a day to provide quick access to media. The custom computer in this case has an Intel Core 2 Duo 1.86GHz processor, 3GB RAM, a 7200RPM hard drive and an NVIDIA 7600GT graphics card. Wprime, with its ability to use multiple processor cores, is an excellent way to force 100 percent use of a processor (thus simulating heavy activities and multitasking).

System Off Idle 1080p Content Wprime
Gateway GT5670 0 78 107 127
Lenovo S10 1 164 184 280
Custom Build 3 98 188

Unsurprisingly, the Lenovo S10 uses a good deal more power than the other systems. Given the hardware in the machine, though, it’s expected. The real surprise is that when processing 1080p content, it used less than an eleven percent electricity premium. This is almost twice the power used by the Gateway GT5670 – which struggled with some high definition video. Despite this 2:1 ratio, you may consider using a high-powered system (if you already have one) to pipe HD content around because of its multitasking capabilities. Instead of running a secondary system to function as a media controller, and then booting up a high-powered rig anyway, it could be worthwhile to just use one machine. The S10 would have the ability to run high definition media and still blow through all but the most demanding tasks.

As time goes on, technology advances and computers evolve. Few components, however, have seen such striking changes in both appearance and function as the monitor. From bulky CRTs that took up the majority of a desk to sleek LCDs with razor-sharp text, computer displays have experienced tremendous change, and their power requirements have changed along with them. LCDs are often touted as being much more energy-friendly than old CRTs, and to a certain extent, this is true. More and more often, though, consumers are buying brighter and bigger monitors. Some even use large HDTVs as primary displays for their computer. LCDs might use less power, but how many times have you seen a 37” CRT? These big screen devices can many times use even more power than the computer itself. You can find out more about how much energy your monitor consumes (along with many other appliances and electronics) at the Energy Star website.

Display Off/Standby Minimum Brightness Maximum Brightness

Lenovo L220x

0 83 96
Sony CPD-G520 0.8 43 80
Sony 40″ KDL-40V3000 0 71 225

The Lenovo L220x used less power than either of the other displays, as expected. What was surprising was that the power used by the G520 (21” CRT) had little variation, whether it was set at the lowest brightness setting or highest. The LCD advantage with regards to power consumption dies when the HDTV is used. Again, it’s not very surprising, but it’s something to keep an eye on if you commonly hook your computer up to such a large display.

They clutter the desk, they tangle the cords, and they also drink up electricity. It’s easy to forget that in addition to the computer and monitor, you might have an external hard drive for backing up files, an external optical drive for disc media, a printer, desk lamp, speakers … you get the idea. Most of the time, these devices carry their own power supplies and generate extra waste heat. They also get left plugged in even when you turn the computer off. All this idling adds up over time:

Accessory Off/Standby Idle Active
Seagate 7200RPM hard drive 0 8-9 10-13
LaCie External DVD+/-RW 30 6-10 12 reading, 21 burning
Samsung ML-2510 laser printer 0 5-500 800
Dell All-in-One 966 inkjet printer 0 10 17
Fluorescent desk lamp (13W) 0 11
Incadescent desk lamp (50W/100W/150W) 0 47/100/148

One thing that’s apparent from looking at these numbers is just how efficient fluorescent lighting is over traditional incandescent. The 13W bulb drew 11W and put out more light than the 50W bulb using 47 Watts. What is almost astonishing, however, is the power draw for the laser printer. Even when idling, the power would occasionally spike into 500W range, and it peaked at 825 or so. Given the respective printer technologies, the laser printer was thoroughly predicted to consume more power than the inkjet, but an order of magnitude is an even larger difference than expected. In a heavy-use setting, such as a small business or home office, a simple laser printer can use more power than most other equipment. At its max, the inkjet printer only used 17W. Even though laser printers will print at a significantly higher speed than an inkjet, it looks like they’ll still use more power by far.

As technology progresses, we find ourselves hopelessly entwined with device after device, and all of these appliances need power. We have iPods, cell phones, portable gaming systems. We have desktops in multiple bedrooms, in the living room, beneath the TV and sometimes even in the kitchen. Being aware of where we use electricity helps us to be aware of where we need to turn it off.

Power meters such as the Kill A Watt are useful tools. They quantify something nebulous – energy consumption – by putting it into concrete, easily understood terms. Having a better understanding of the power cost your daily habits incur makes it easy to find and trim areas where you might be carrying a little extra electric baggage. This is important knowledge when you might be paying upwards of 14¢ per kilowatt-hour.

The biggest and best tip that can be given is to TURN OFF YOUR COMPUTER. It’s easy to shrug the idea that turning off your unused desktop(s) every night can save power, but look at the facts: leaving a powerful computer like the Lenovo S10 on for a solid month, just idling, will cost an average of twelve dollars. It gets worse. Consider a family with children. They might have a computer in the family room, and two more in various bedrooms. Even if they used as little power as the Gateway GT5670, those three computers cost $17 a month to just sit there unused. This doesn’t even take displays into account, many of which are left on with screen savers constantly redrawing. If it’s hard to get into the habit of doing this, set the power options in your OS to do it for you after long periods of inactivity.  If it’s absolutely imperative to leave the computer on, consider cutting down on the time it takes for the desktop to go to sleep.  Waking from sleep can take only a few seconds compared to a cold boot, and the energy savings over typical idle states can be more than ninety percent!

Here are a few more tips on conserving power around your computer:

  • Consolidate your machines. There’s little to be gained by having multiple systems each performing a single task. If one machine is capable of handling more than one job, let it.
  • Turn off your displays when they’re not being used. Screen savers are pretty, but all they do is waste electricity these days.
  • Speaking of displays, a smaller monitor will tend to use noticeably less electricity than a bigger HDTV, even if the resolutions are the same.
  • Just because something says it’s off, don’t believe it. Unplug unused and fully-charged devices; the power adapters may still draw a current. To make this easier, plug multiple chargers and adapters into a power strip. The main switch can be tripped to easily cut all power to the gathered devices. No more vampire power, no more electric waste.
  • Replace your desk lamp with a more energy efficient model. Fluorescents, and more recently, LEDs, have come a long way. Swapping your old incandescent bulb for a new fluorescent one when it dies can save over 50W.
  • A good set of headphones will draw less power and many times sound better than the sets of speakers that are sold with your computer.
  • Replace some of your desktop’s components with low-power or “green” counterparts, such as Western Digital’s 2TB Caviar Green drive.  Lots of space at half the energy cost.

While this guide is far from comprehensive, hopefully it’ll help you find areas in your life where you can scale back and save a little money. Try calculating how much the energy your computers use costs. You might end up surprised.  Have any more eco-friendly tips to share?  Leave us comments below!



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