Computer Power Consumption

Created By Paul BriskeyFebruary 18, 2008

Outline

• Computer Power States

• Computer Power Consumption Factors

• Notes On Energy Star

• Power Test – System Configuration

• Power Test Results

• Conservation Steps and Software Notes

• Changing Power Management Settings

• Sources

Computer Power States

Power State Description

S0 (At Desktop) Normal working state (either idle or active). Computer is ready to go.

S3 (Sleeping) Monitor, HDD, and other peripherals are turned off but RAM is still on and holding data. Fastest to wake up.

S4 (Hibernating) All data in RAM is stored to the HDD and everything is shut down. Medium amount of time to wake up.

S5 (Power Off/Mechanical Off) Computer is off but still plugged in. Must go through full boot process.

G3 (Power disconnected) Power strip is off or computer is not plugged in. Must go through full boot process.

Computer Power Consumption Factors

• Everything makes a difference– Power consumption is based on voltage levels and current

requirements. These will vary drastically not only with component attributes (i.e., processor speed), but also between brands.

– Power management options in the operating system as well as in the motherboard BIOS also change consumption.

• Performance often precludes power savings– Increases in speed result in more power use. For example, an

increase in memory speed causes it to become unstable so the memory voltage is increased. This directly results in more power use.

Notes On Energy StarFor Computers/Motherboards

• Energy Star is a product certification that manufacturers can apply for.

• Each product type (desktop, server, etc.) has several categories, each with different qualifications.

• Compliance is taken very seriously since ONE failed test at any time prohibits certification for the failed product indefinitely.

• Test conditions are specified by the manufacturer. Therefore, an E-Star compliant system might only pass when specific parts are used and many system options are disabled.

Power Test – System ConfigurationGaming System Multimedia System Energy Star Board

Board Intel D975XBX2 NVIDIA nForce660

Processor Intel Core2 Extreme (45nm, 1.165V)

Intel Pentium Extreme (65nm, 1.525V)

Multi-core

RAM 2GB PC2-5300 (1.8V) 4GB PC2-6400 (2.2V) >2GB

HDD 500GB SATA II200GB SATA II300GB SATA II

500GB SATA II240GB IDE120GB IDE

>2 HDD

Graphics Card GeForce 8800GTS-512 GeForce 7900GTX-512 >128MB dedicated

Sound Card X-FI Xtreme Music X-FI Xtreme Music None

Other TV Tuner Card, PCI USB Card, 4- 120mm and 1- 140mm case fans, DVD ROM (IDE), DVD-RW (IDE)

TV Tuner Card, 2- 120mm case fans, Wireless-G Network Card, 13in1 Card Reader

TV Tuner/Video Capture Card

Note: Parts list is not exhaustive. Energy Star configuration for Class C desktop board

Power Test Results

Power State Gaming System Multimedia System E-Star Board*

S0 (Active)** 250W 300W -

S0 (Idle) 163W 212W <95W

S3 (Sleep) 7W 6W <4W

S5 (Off) 6W 5W <2WkWh/

monthCost/month @ $.10/kWh

kWh/month

Cost/month @ $.10/kWh

kWh/month

Cost/month @ $.10/kWh

S0 (Idle) 117.36 $11.74 152.64 $15.26 <68.4 <$6.84

S3 (Sleep) 5.04 $.50 4.32 $.43 <2.88 <$.29

S5 (Off) 4.32 $.43 3.6 $.36 <1.44 <$.14

*E-Star board power requirements are based on the Intel Desktop Class C standard (classes A and B have more stringent power requirements).**Active Test: Running 3DMark06

Conservation Steps & Software Notes

To Conserve Energy:• Turn your computer off at night. (Basic)• Change power management options on your computer.

(Intermediate)• Disable unnecessary motherboard options. (Advanced)• Disable unused hardware in the device manager or set it to enter

low power mode when not used. (Advanced)

Using Software:• You can download software to change power management options for

you. Many systems already include this.• If you can do it yourself (it is very straight forward) you will avoid another

program running in the background slowing your computer down.• This software is not capable of changing any motherboard options in BIOS

Changing Power Management Settings

3. Select a power scheme and hit OK

1. Right click on the desktop and select “Properties”

2. Select the “Screen Saver” tab and click “Power…”

Explore this dialogue to find other options for power saving

SourcesBolioni, Thomas, et al. “Energy Star* System Implementation.” April 2007.

Intel Corporation. 18 February, 2008. <http://cache-www.intel.com/cd/00/00/33/90/339085_339085.pdf>