Overview

This article provides an overview of Windows low power states, describes their benefits, and recommends how to achieve the best combination of energy savings and low impact on end users.

Environment

Product

• All Verdiem Surveyor versions

Operating system

• Windows XP
• Windows Vista
• Windows 7

Information

The power states that Surveyor monitors for PCs include: on, idle, sleep, hibernate, and off.

When a PC is on and being used actively, it consumes 60-250 watts of electricity. When you want to put a computer into a low power state, you have the following options.

• Sleep (also called Standby) - This state uses the least amount of power while leaving the computer turned on. Programs or documents that are open are written to computer memory and remain open while the computer is in sleep mode. When you return and wake the computer, you can pick up where you left off.
• Hibernate - This state saves open documents to the disk, close programs, and then turns off the computer. In most computers, you can wake the computer and resume working by pressing the power button.
• Off -  All programs are closed, the operating system is shut down, and the computer is powered off. The operating system and all programs must be restarted when the computer is turned on. In the Off state, most modern machines use a small amount of power, which is for the network card to listen for a Wake on LAN magic packet.

The following table shows the advantages and disadvantages of low power states as they relate to power management.

The Benefits of Transitioning to Sleep

Although the off and hibernate states provide some increased energy savings over sleep (known as standby in Windows XP), the savings are so insignificant that the disadvantages far outweigh the savings. Wake and network issues are common when the computers have been set to Hibernate or Off.

To get a clearer idea of the trivial differences in savings, energy usage data based on manufacturer specifications of 100 systems is provided below:

• Standby: 3-5 W
• Hibernate: 2-3 W
• Off: 2-3 W

When a computer or any device goes into a lower power state, users expect it to wake up quickly as soon as they try to access it. Using policies that transition PCs to sleep offer the fastest wake-up experience for users and significant energy savings over time while having the least impact on productivity.

Keys to Intelligent Power Management

Smart power management starts with:

• Understanding PC power states and how they affect PC energy consumption.
• Knowing how much energy PCs and devices in your organization use, why, and at what times of day users are most active.

Surveyor helps you gather data on the energy use and user activity in your organization and reports on that energy use to help you determine your organization’s baseline, which is the amount of energy used by PCs and network devices before centralized power management has been implemented and enforced.

After you determine your baseline energy use, you can assess daily and weekly usage patterns to determine what policies should be enforced at particular times of the day and week.

The policies you enforce should reduce energy consumption, yet not interfere with user productivity or IT software maintenance windows. Surveyor allows you to apply power settings on a scheduled basis to gracefully transition PCs into low power states based on inactivity.