Windows Vista Energy Conservation Abstract The Windows Vista operating system features significant changes to power management infrastructure, functionality, and default settings. These changes impact how PCs running Microsoft Windows consume energy. This paper outlines the potential energy savings available when deploying Windows Vista and the significant changes from Windows XP. These savings are presented in terms of both financial and environmental impact. The current version of this paper is maintained on the Web at: http://www.microsoft.com/whdc/system/pnppwr/powermgmt/vistaenergyconserv.mspx References and resources discussed here are listed at the end of this paper. Contents Introduction... 3 Broad Deployment of Energy-Saving Features... 3 Windows Vista Features that Promote Power Savings... 4 PC Power Consumption... 5 Calculating Energy Savings... 5 Financial Impact... 5 Environmental Impact... 6 Environmental Impact Summary... 7 Future Hardware and Energy Consumption Expectations... 7 Conclusion... 8 References... 9
Windows Vista Energy Conservation - 2 Disclaimer This is a preliminary document and may be changed substantially prior to final commercial release of the software described herein. The information contained in this document represents the current view of Microsoft Corporation on the issues discussed as of the date of publication. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information presented after the date of publication. This White Paper is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS DOCUMENT. Complying with all applicable copyright laws is the responsibility of the user. Without limiting the rights under copyright, no part of this document may be reproduced, stored in or introduced into a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise), or for any purpose, without the express written permission of Microsoft Corporation. Microsoft may have patents, patent applications, trademarks, copyrights, or other intellectual property rights covering subject matter in this document. Except as expressly provided in any written license agreement from Microsoft, the furnishing of this document does not give you any license to these patents, trademarks, copyrights, or other intellectual property. Unless otherwise noted, the example companies, organizations, products, domain names, e-mail addresses, logos, people, places and events depicted herein are fictitious, and no association with any real company, organization, product, domain name, email address, logo, person, place or event is intended or should be inferred. Microsoft, Superfetch, Windows, and Windows Vista are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. The names of actual companies and products mentioned herein may be the trademarks of their respective owners.
Windows Vista Energy Conservation - 3 Introduction To most people, it is common sense that leaving a light bulb on all the time is a waste of energy. However, many organizations do exactly that with their PCs. To make machines available for software installs, patching, and remote access, many organizations instruct their employees not to turn off their machines at night. Usually, these machines are sitting idle and consuming power, without producing any useful work. For example, imagine a 100-watt (W) light bulb powered on 24 hours (h) a day, 7 days a week. A single day s worth of continuous usage would result in a consumption of 2,400 watt-hours (Wh) or 2.40 kilowatt-hours (kwh), that is, 24 h x 100 W = 2,400 Wh. According to the Electric Power Monthly report from the U.S. Department of Energy, the average national commercial electricity price year to date for 2006 is $.0931 per kwh. Therefore, a single day s usage would cost just over $ 0.22. Although this seems like a small amount, this single bulb would consume $81.56 per year. Let s assume that this bulb is an exterior porch light. During daylight hours, having the porch light on is unnecessary. It could also be turned off during the hours when people are normally asleep. For the sake of this example, let s assume that this light is turned on only between the hours of 6:00 PM and midnight. This would be a 75- percent reduction in power consumption. This example bulb would now cost only $20.39 to power per year a savings of $61.17. This document outlines the steps taken to estimate the impact of PC energy savings based on moving from a model of leaving the PC on constantly to a model that leverages the low-power "Sleep" feature in Windows Vista while the PC is not in use. Examples in this paper are based on published power consumption data from the Lawrence Berkeley National Laboratory (LBNL), the U.S. Department of Energy, and the U.S. Environmental Protection Agency (EPA) Energy Star program. The potential savings are presented in terms of both financial and environmental impact. Broad Deployment of Energy-Saving Features Windows Vista is Microsoft s most energy-efficient operating system to date. Enterprise IT staffs are very aware of the energy costs for operating PCs and the associated heating, ventilation, and air-conditioning (HVAC) required. As organizations are determining when they should upgrade, the potential for significant total-cost-of-ownership (TCO) savings is a compelling reason for deploying Windows Vista. Energy costs are part of TCO for IT departments. With concerns about global warming, energy shortages, and potential oil crises, an energy-efficient operating system is one way in which Microsoft demonstrates that it is remembering environmental factors as it delivers the next operating system. To date, PC users have had few options for how to conserve energy when using their PCs. This applies both to while they are using the PC and while they are not. When not using their PC, many people just leave it on or shut it down completely to save energy, most not knowing Sleep is as energy efficient as shutdown. If users shut down their PC after each use, they must sit through the boot process each time they want to use their PC again. Using Sleep allows significant energy savings when the PC is not in use and the ability to quickly resume (in less than 2 seconds). Most new desktop processors have adopted support of operating system managed processor power management. As this becomes pervasive in PC platforms, the operating system can automatically scale up or scale down the performance of the platform processor, according to demand. This is done with no perceivable impact
Windows Vista Energy Conservation - 4 to performance. Windows Vista goes beyond Windows XP to do this by default on all PC platform types, from mobile to server. Windows Vista Features that Promote Power Savings Windows Vista promotes power savings because of the following features: Centralized manageability for IT professionals: Power settings that are per-machine Powerful command-line configuration tool (powercfg.exe) Group policy support for all inbox power settings Default settings optimized for best user experience and energy savings: A default time out that automatically blanks the display A system idle timer for entering Sleep Dynamic processor power management for capable desktop and laptop hardware Default Off that is actually Sleep (Start menu, sleep power button, button, and lid switch) Performance: Immediate responsiveness to Sleep or Resume Consistent Sleep resume performance by using Microsoft Superfetch advanced memory management technology Enhanced Plug and Play performance Reliability: Applications, services, and drivers that cannot block Sleep transitions Improved idle detection that helps ensure that a PC awakened from the network or for scheduled activity returns to Sleep after 2 minutes of idleness Built-in diagnostics for Sleep and Resume that: Return reliability data to Microsoft if a user joins the Customer Experience Improvement Program Enable Microsoft to proactively address Sleep reliability issues if they arise (that is, post-release driver updates that impact Sleep and Resume) Hybrid Sleep (on desktops): A system that resumes from disk if power is lost in Sleep (nonvolatile, like Hibernate) Notebooks do not require hybrid sleep because they have a battery for reliability A normal Resume from memory (fast, like Standby) A combination of Standby (Suspend to RAM) and Hibernate (Suspend to Disk) Simple "Off" metaphor No requirement for users to distinguish between Standby and Hibernate they merely choose "Sleep" and it just works
Windows Vista Energy Conservation - 5 PC Power Consumption Values for the amount of energy that a typical PC and display consume are based on a 2002 study by LBNL. Table 1 contains the mean values for Intel Pentium 4 machines and for 17-inch CRT and LCD displays. Table 1. Power Usage for Desktop PCs (watts) Idle Sleep Savings Mean of LBNL-measured Pentium 4 machines 67.3 3.3 64.0 Mean of 17-inch CRT monitors 61.2 1.8 59.4 Mean of 17-inch LCD monitors 35.3 2.3 33.0 Power consumption was measured in both the on-but-idle state and the low-power Sleep (Suspend to RAM or ACPI S3) state. The idle state was characterized as: An idle Windows desktop on a running, but otherwise quiescent system No software running other than the operating system Display on (not blanked) Calculating Energy Savings To project potential energy savings when the PC is not in use, power savings were calculated by comparing a PC left running constantly versus a PC running 10 hours a day, 5 days a week, and otherwise using the Sleep feature in Windows Vista while the PC is not in use. To calculate these savings, only the nonworking hours, or 14 hours out of 24, need to be considered. 24 hours x 365 days per year = 8,760 hours per year 10 workday hours x 5 working days per week x 52 week = 2,600 operating hours 8,760 hours per year 2,600 operating hours = nonuse hours per year The following calculations are based on annual energy savings (in kwh) by using the Sleep feature versus leaving the PC on constantly: (Idle Power Draw Sleep Power Draw) x 6,160 nonuse hours = Annual Savings Table 2 outlines the energy savings achieved based on the values above. Table 2. Energy Savings for Desktop PCs (kwh) Typical P4 machine with 17-inch CRT Typical P4 machine with 17-inch LCD Financial Impact Power draw per year (idle) Power draw per year (Sleep) Savings per year (Sleep vs. idle) 791.56 31.42 760.14 632.02 34.50 597.52 The financial benefit is determined by multiplying the energy savings by the cost of electricity purchased from the power utility, expressed as a price per kwh. Energy costs vary geographically, by season, and due to other market influences. The costing price per kwh used was $0.0931. This is the July 2006 year-to-date average for the commercial sector, as reported in Electric Power Monthly from the U.S. Department of Energy.
Windows Vista Energy Conservation - 6 This estimate does not include other potential savings, such as lower HVAC operating costs due to greatly reduced thermal output when the PC is in the Sleep state. Annual Per-PC Power Cost Savings Using Sleep (Typical Pentium 4 PC with 17-inch CRT) 760.14 kwh x $0.0931 = $70.77 Annual Per-PC Power Cost Savings Using Sleep (Typical Pentium 4 PC with 17-inch LCD) 597.52 kwh x $0.0931 = $55.63 Multiplying the single PC values above by PCs deployed with Windows Vista, one can estimate the financial savings for an organization. For example, an organization with 1,000 Pentium 4 PCs with 17-inch CRTs would reduce costs by about $70,770 by placing PCs in Sleep versus leaving them on constantly. $70.77 savings per PC x 1,000 PCs = $70,770 Environmental Impact Creating energy has the potential harmful impact of contributing greenhouse gas to the atmosphere. Conversely, reducing the overall power that is consumed by PCs when not in use produces a significant positive impact on the environment. The following information illustrates the environmental impact associated with using the Sleep feature in Windows Vista on a typical Pentium 4 with a 17-inch CRT monitor. Carbon Dioxide Emissions (Greenhouse Gas) According to the EPA, generating 1 kwh of electricity in the United States results in an average 1.55 pounds (lb) of carbon dioxide (CO 2 ) emissions. Therefore, saving 760.14 kwh of electricity eliminates 1,178.22 lb of CO 2 emissions due to energy generation for the period of time in which the PC is not in use. Each of these PCs left on when not in use results in over a half ton of greenhouse gas annually. Automobile Carbon Dioxide Emissions According to the EPA, the average automobile in the United States generates 11,560 lb of CO 2 emissions annually. The 1,178.22 lb of CO 2 emissions saved by eliminating 760.14 kwh equates to 10.2 percent of the emissions that the average automobile generates. Ten of these PCs left on when not in use results in the equivalent of one more car on the road in terms of greenhouse gas contribution annually.
Windows Vista Energy Conservation - 7 Carbon Dioxide Emissions as Compared to Tree Plantings ICF Consulting calculates, using an average carbon sequestration rate, that 1 acre of forest sequesters 7,333 lb of CO 2 emissions per year. The 1,178.22 lb of CO 2 emissions saved per year in our example represents 0.161 acre of trees not required to sequester these CO 2 emissions. For every 6 PCs left on when not in use, an acre of trees is required to sequester the greenhouse gas that is released due to generating the power to leave them fully on while not in use. Home Annual Energy Use The Department of Energy calculates that the average American home uses 10,896 kwh of electricity per year. Therefore, the 760.14 kwh of energy saved annually in our example translates into 7 percent of the average home energy use. Environmental Impact Summary Table 3 summarizes these environmental impacts. Table 3. Environmental Savings per Windows Vista PC Per PC with 17-inch CRT Per PC with 17-inch LCD Energy savings 760.14 kwh 597.52 kwh CO 2 emissions reduction 1178.22 lb 926.16 lb Comparable auto emissions removed 0.102 auto 0.080 auto Trees not required to sequester CO 2 emissions 0.161 acre 0.126 acre Equivalent homes powered 0.070 home 0.055 home Multiplying the single PC values in Table 3 by PCs deployed with Windows Vista, one can estimate the reduction in environmental impact for an organization. Using the above example of 1,000 PCs with 17-inch CRTs, CO 2 emissions are reduced by over 1 million pounds per year when the Sleep feature is on versus leaving the PC on constantly. 1,178.22 lb CO 2 per PC x 1,000 PCs = 1,178,220 lb CO 2 A thousand PCs using this Sleep model with Windows Vista would save over 1 million pounds of greenhouse gas annually! Future Hardware and Energy Consumption Expectations The above estimates are based on an average consumption of 67.30 watts (not including the display) as calculated in 2002 by LBNL. In recent years, higher idle power consumption in PCs has been observed. Today it is not uncommon to have machines that consume more than 100 watts when idle. Significant work has been done to offset these rises in consumption through advancements such as processor power management; yet even with these savings, idle power overall has been increasing. Processor power management is relatively new to desktop PCs and is enabled by default in Windows Vista, which delivers a significant improvement for desktops.
Windows Vista Energy Conservation - 8 In an effort to combat this rise in power consumption, the EPA is updating the Energy Star program for personal computers. The Energy Star 4.0 program is scheduled to take effect in January 2007. Machines that meet the requirements will be allowed to display the Energy Star logo. The updated Energy Star standard divides the desktop PC space into Categories A, B, and C, based on the hardware configuration of the machine. For the Energy Star program, the EPA has set a limit on the amount of power a compliant machine can consume while idle. The limit for all categories of machines in the Sleep mode is 4 watts. Table 4 outlines the categories and their respective idle power limits. Table 4. Energy Star Levels for Tier-1 Desktops Category Characteristics Idle power limit (watts) A Machines that do not qualify under Categories B or C 50 B Machines with multicore processors and 1 GB or more of 65 memory C Machines with multicore processors and 1 GB or more of memory, GPU with 128 MB or more of memory, and additional peripherals such as a second hard drive or TV tuner The updated Energy Star program establishes the expectations for power consumption for PCs when in Sleep or "On," but idle. Using these categories and the previous model for saving energy when PCs are not in use, Energy Star compliant machines would conserve between $45 and $71 annually by introducing this Sleep versus On duty cycle. Table 5 details the achievable energy and cost savings at the limits set forth by the EPA. These values include a 17-inch LCD display for direct comparisons. Because LCD displays are expected to dominate new hardware shipments, no numbers for CRTs are shown in this section of this paper. The paper did include CRT numbers earlier because there will be large deployments of Windows Vista to older PC seats in the installed base that are still CRT based. Table 5. Savings in Energy Star Tier-1 Desktops Desktop category Power draw per year idle (kwh) Power draw per year Sleep (kwh) Savings per year Sleep vs. idle (kwh) 95 Savings at 0.0931 per kwh ($) A 525.45 38.81 486.64 45.31 B 617.85 38.81 597.04 53.91 C 802.65 38.81 763.84 71.11 Conclusion Leaving PCs on constantly consumes large amounts of energy mostly wasted energy. Organizations should be aware of this and the associated impact to the organization s bottom line as well as the environmental impact. Wasted power results in higher utility bills and significant environmental impact. Using the Sleep feature on Windows Vista PCs offers organizations significant cost savings, helps to maximize energy conservation, and improves the overall user experience through instant on accessibility.
Windows Vista Energy Conservation - 9 References Lawrence Berkeley National Laboratory, University of California "Energy Use and Power Levels in New Monitors and Personal Computers," Paper LBNL-48581, July 23, 2002 http://repositories.cdlib.org/lbnl/lbnl-48581 Energy Information Administration, U.S. Department of Energy Electric Power Monthly,, Table 5.3, "2006 Year-to-Date Average Cost per kwh" http://www.eia.doe.gov/cneaf/electricity/epm/epm.pdf Average Residential Monthly Use, EIA Electricity Quick Stats, Yearly average use calculated from monthly average use (908 kwh) http://www.eia.doe.gov/cneaf/electricity/esr/table5.xls Energy Star (a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy) "Energy Star National Average for Energy to Carbon Emissions in the United States" "Energy Star National Average for Carbon Emissions to Cars in the United States" http://www.energystar.gov/index.cfm?c=energy_awareness.bus_energy_use ICF Consulting "Emissions Factors, Global Warming Potentials, Unit Conversions, Emissions, and Related Facts," November 23, 1999 The factor in turn is calculated by ICF Consulting from Sector-Specific Issues and Reporting Methodologies Supporting the General Guidelines for the Voluntary Reporting of Greenhouse Gases under Section 1605(b) of the Energy Policy Act of 1992, Appending 5E, using an average carbon sequestration rate, across tree types and land status, of 5 year old trees. http://www.p2pays.org/ref/07/06861.pdf