Tip of the Trade: Saving on Power and Cooling

By Carla Schroder (Send Email)
Posted Jul 9, 2007


Conserving electricity is always a worthy goal, and is more so in the summer months. Reducing the amount of power that desktops and servers consume also reduces heat, which reduces the overall cooling load. Power supplies, CPUs, CRT monitors, hard drives and high-end graphics cards aren't major energy hogs all by themselves, but when they run in herds, power consumption adds up.

Energy conservation can be as simple as shutting off servers at the end of the day or using efficiency ratings on power supplies to guide purchases. To get started, the Kill-A-Watt cumulative kilowatt-hour monitor is a quick and inexpensive way to measure how much energy you're saving or consuming.

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The Kill-A-Watt cumulative kilowatt-hour monitor is a quick and inexpensive way to measure how much energy a computer or monitor is using. The Kill-A-Watt sells for around $30. It measures volts, amps, watts, Hz and VA (volt-amperes). It's interesting to compare the differences between a system under load, an idling system and a system that is supposedly "off." Nowadays, off no longer means off, but rather "on a little bit." A quick way to measure this is to hit all the off switches, and then enter the room in the dark. How many LEDs are shining forth in the darkness? Sometimes enough to cast a shadow.

Replacing a CRT monitor with an LCD one is a fairly painless way to save energy, save space, generate less heat and, as a bonus, get a better-quality screen. One of my personal peeves is mean cheapskate bosses that keep old dim blurry monitors in service far too long. This is bad for eyes — don't be cheap on the wrong things. A 19" CRT draws around 100 to 200 watts when it's working, and around 30 watts when asleep. A 19" TFT is not only bright and crisp and beautiful, modern ones typically require 55 watts under load, and 1-5 watts in sleep mode.

When AMD and Intel raced to produce ever-more powerful processors, mitigating heat and energy consumption took a back seat. So not only were the CPUs hungry little electricity eaters, they also needed considerable cooling. Now, both vendors' contributions help enable CPUs to run faster or slower according to demand, and the chips are cooler and more energy-efficient.

Look for the efficiency rating on power supplies. An inefficient power supply runs at less than 70 percent efficiency. To get an Energy Star rating, a power supply must reach at least at 80 percent efficiency.

A simple way to save energy is to turn things off. When users go home, their desktop PCs don't need to be running. There may be some servers that can be shut off as well.

Server consolidation is another good way to lower energy costs. Several hard drive manufacturers make server-quality 2.5" drives for racks and blades, which use less power and throw off less heat. This article has some additional helpful information.

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