Computers are the corporate drones of American business, a massive army of silicon grunts stationed in every office and cubicle across the country. They're indispensable to the hum of modern commerce, they're growing more powerful at an exponential rate-and oh, yeah, they're absolute gluttons for electricity. Consider this: Computers and monitors account for a whopping 9 percent of the typical business's electric bill. Across the country, there are 180 million computers in use, according to the Natural Resources Defense Council (NRDC), a total that accounts for a full 2 percent of the United States' colossal electricity consumption.

Computer equipment uses lots of electricity in part because it's inefficient at converting it to pixels and printouts; as much as 30 percent of a typical computer's electrical input ends up being transformed into heat. And that's bad for a couple of reasons: For one thing, heat makes the equipment wear out faster. Even worse, though, is the fact that because every PC is also functioning as a heater, your building's cooling system is forced to work overtime in the summer. That drives your electric bill even higher. A bigger problem than you thought, huh?

It doesn't have to be so bad. When it's time to replace equipment, you can choose energy-efficient computers and monitors that'll get the work done while using a lot less power. Let's start with the computer itself.

Concentrate on your form: desktop vs. laptop
Desktop computers come in lots of different configurations, but let's start with the most common: the beige box (which houses the computer circuitry) with a cathode-ray tube (CRT) monitor. A basic computer typically consumes about 120 watts, and the monitor sitting on top of it can slurp down another 80 watts, for a grand total of 200 watts. In comparison, the typical laptop consumes a miserly 30 watts, period. This is because even though your laptop tends to die 90 minutes out of LAX, it's actually designed to maximize battery life by minimizing power consumption (the short lifespan of rechargeable batteries-well, that's another story). Laptops are built with energy-efficient displays, hard drives, and processors, and the result is a far more energy-efficient device than the hulking machine on your desk. Notebooks were once an extravagance allotted only to a company's road warriors, but today even dirt-cheap notebooks exceed the performance needs of almost all business users.

So what does opting for a laptop instead of a desktop mean for your bottom line? You should see energy savings of 50 percent to 75 percent. And even if you choose a bigger "desktop replacement" laptop, with a larger screen and less aggressive power-management settings, you can save better than 50 percent.

Less is more: buy only as much PC as you need
If the higher initial cost of a laptop outweighs the energy savings, you can still configure your next desktops to be more energy-efficient. What's inside the box makes a big difference. For example, consider a high-performance computer that includes two 3 GHz processors and a high-performance video card-the kind of computer that might be used for 3D animation, DNA sequencing, or hardcore gaming. At idle, it consumes 140 watts; at peak output, its energy use can spike to more than 600 watts. That's absolute overkill for email and spreadsheets, which account for the mundane majority of most office work. Even more amazing, at full blast the heat output of a high-powered computer like this can approach a startling 2,000 Btu/h (a small space heater produces about 10,000 Btu/h). That's heat that your air-conditioning system has to contend with in the summer, and that makes your electric meter spin dizzyingly fast.

So don't get a computer with more processing power than you need, and go easy on the unnecessary extras, too. Even a high-performance video card in an otherwise unremarkable computer can increase energy consumption by as much as 100 watts when it's running 3D operations. Some of these cards actually run so hot that they require their own cooling fans, which further increase energy demands.

Here's looking at you: the monitor
You've got two basic choices when it comes to computer monitors: the old-school CRT and the relatively newer liquid crystal display (LCD). CRT monitors are less expensive and render colors a little more accurately, but LCD monitors are less bulky and have a smaller physical footprint. More important, they use less electricity-a lot less. For example, a 17-inch LCD consumes 51 percent as much power as a 17-inch CRT (a typical 17-inch CRT draws about 80 watts). What's more, they generate minimal heat compared with CRTs.

While the initial expense of an LCD is greater than that of a CRT, the total cost of ownership is less because, in addition to the energy savings, they have twice the lifespan.

Set for sleep: power-management features
No matter which kind of computer or monitor you opt for, it's not just what you have-it's how you use it. From an environmental perspective, consider that just one computer and its monitor left on after business hours will account for nearly one ton of CO2 emissions per year.

Almost all operating systems in use today feature power-management settings that put computers and monitors into low-power "sleep" modes after a specified idle time. Turning on monitor power management, for example, can save $10 to $30 per monitor annually, while computer power management, which lets inactive computers take an energy-conserving nap, can save $15 to $45 per desktop computer annually. Keep in mind that any screen saver that shows an image-such as the ones that turn your monitor into a matrix of dancing lines or display a cute kitten in a flowerpot-actually uses just as much energy as it takes to display email or a word-processing document; a fade to black is a better option when you're away from your desk. "Kill your screen saver," advises Noah Horowitz, senior scientist at the NRDC. "You can cut your electric bill by at least $50 a year."

If you're buying equipment for a business (large or small) you can have an even greater impact. With your generous tax funding, the Environmental Protection Agency has created boilerplate contract language that you can weave into your next purchase agreement. It stipulates, for example, that your vendor must provide Energy Star-labeled computers (see below) that have their power-management features enabled and that, if networked, will go into sleep mode when idle but will wake up in response to certain network signals (which saves your IT person a big headache). You can find this contract language here.

Star qualities: look for the label
Whatever else you do, you should buy computers and monitors that carry the EPA's Energy Star label. And nowadays, it's actually pretty hard to find a computer or monitor that isn't Energy Star-compliant; about 98 percent of computers and 95 percent of monitors now sold meet the standard. These products use less energy when they're on, and when they're not in use they automatically enter a low-power mode after a preset amount of time. While the Energy Star standards aren't mandatory, most computer manufacturers will meet them to make sure they get government business-Uncle Sam, after all, is required to buy Energy Star-compliant computers to make taxpayers happy.

The latest version of the Energy Star specifications, which went into effect on July 20, require that computers using an internal power supply (the part that converts alternating current from the wall socket to the direct current used by the computer) must be at least 80 percent efficient in conversion. In contrast, "current power supplies are between 60 percent and 70 percent efficient," says Ryan Rasmussen, a senior program manager at Ecos Consulting, which developed the "80Plus" standard adopted by the EPA."

On average, Energy Star-certified computers are 65 percent more efficient than conventional models. And monitors with the Energy Star label use 90 percent less electricity than a standard monitor without power management. You can find a complete list of all Energy Star computers (at last count, nearly 6,000 models) and monitors at Energy Star.

You do the math: what it will cost
Since this is all about saving money, here's an equation to help you calculate the cost of electrical consumption for any piece of equipment (don't worry-the math is strictly middle-school):

Annual cost = (watts consumed x hours per day in use x days per year in use) ÷ 1,000 x rate per kWh

To calculate the annual energy cost for a computer setup, consider a 120-watt beige box with a 150-watt CRT monitor. Assume that it's used for 8 hours per day and 250 days per year, and that electricity costs 10 cents per kilowatt-hour (kWh). Plug these numbers into the equation and you'll find that it costs about $54 dollars per year in electricity, or $162 over a minimum three-year lifespan. In comparison, a typical laptop eats up a measly $6 in electricity every year.

The best part of this equation, of course, is that every dollar you save on your bottom line leaves the world a little greener.

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