The University of Western Australia – IT Policy Committee

Guidance on PC Power Management

Adopted by the IT Policy Committee on 2-Sep-02.

CONTENTS:

1. Background
2. Taking Energy Saving into Account at PC Purchase
3. Turning Computer Off:  Not Damaging
4. Understanding How Much Saving Could be Made
5. How to Activate Power Saving

1. Background:

It is currently estimated that there are 6,500 personal computers installed at the University, for use by staff, students and visitors.  If all these were turned on together (as they frequently are during the normal working day), then they would consume a significant amount of electricity (directly, to power them, and also indirectly to power airconditioning);  it has been estimated that this now represents about 10% of the electricity consumed by the University.

Of course, when these are in use, little can be done to reduce this fuel expense.  However, it is also thought that a considerable percentage of these computers are left running for protracted periods when not in use;  some are even left running overnight and at weekends.  Not only does this consume considerable amounts of energy unnecessarily, but it may also represent a fire hazard.

The following information has been assembled in the interests of encouraging more concerted attempts to conserve this energy.

2. Taking Energy Saving into Account at PC Purchase:

The University has already established a guideline for taking energy saving issues into account when purchasing a PC;  see

http://www.ofm.uwa.edu.au/ops/enviro/energycon.htm and http://www.ofm.uwa.edu.au/ops/enviro/computerpurch.htm

3. Turning Computer Off:  Not Damaging:

Some people may leave computers switched on in the belief that to turn them off (say) each day may lead to component damage.  In particular, it has been thought that disk drives should be left spinning.

In fact, while this may have been true for some models some time ago, this is not the case any longer.  For instance, the University of NSW has undertaken a survey of a wide range of PC suppliers, all of which confirmed that it was more damaging to leave computers switched on indefinitely than to turn them off overnight.  See http://www.energy.unsw.edu.au/unswitch/experts.html

4. Understanding How Much Saving Could be Made:

Many users probably assume that PCs do not consume much electricity, so that to leave them running does not really waste much energy.

The following are typical power consumption figure for a modern PC:  System unit 25W;  Monitor 100W  (30W for an LCD monitor).

A personal computer therefore typically consumes about 1MWh per year;  given that the University is currently charged, on average, at a rate of 10.5c/kWh, this amounts to $100/year;  given that the normal working week only represents about 25% of this, the wastage comes to about $75/year.  This may sound like a lot, but when multiplied by 6,500 amounts to nearly $500,000 – as much as 25% of the total University power bill of about $2million/year.

Even if only monitors were turned off, only at night, the difference would amount to nearly $400,000/year.  Now, of course, many computers and monitors are turned off during inactive periods, so some of these savings are already being achieved.  Nonetheless, they illustrate the fact that savings could be very significant indeed – it is estimated that savings of around $200,000 (10% of the whole power bill) could be saved if those monitors which are not currently turned off were to be.

The US Government Department of Energy has a very helpful Website (see http://http://www.energystar.gov/index.cfm?c=power_mgt.pr_pm_step1), which has an energy saving calculator to help recognise the extent of savings possible.  The following results (in $A) were obtained by estimating the effects of employing energy saving on all the University’s 6,000 computers (during after-hours periods) versus an estimate of only about 35% at present:

5. How to Activate Power Saving:

Many computer users may actually not realise that their computers are fitted with energy saving features.  For instance, the monitor can be set to turn off automatically after a set period of inactivity, eg 10 minutes.  It will turn back on if the mouse is moved or other user activity occurs.

This can be activated through the Start – Settings – Control Panel – Display – Screen Saver sequence of windows on a PC (similar procedures are available on Macs and Unix systems).

It should also be noted that activating a “screen saver” does not usually actually save any energy (thus the above Control Panel sequence is actually a little misleading).  A screen saver normally only prevents the screen from having a particular image get “burned into” the phosphor from having it stay on the screen for very long periods.  What you need to activate is “energy saving”, not “screen saving”.

Note that if computers are used to participate in “spare PC processing power” projects (like SETI@home – see http://www.its.uwa.edu.au/policies/commspolicies/managesuptrain/sparecapacity), then it is absolutely vital that as much energy saving as possible be undertaken – do not participate until you have successfully activated appropriate power saving measures (especially so that monitors turn off – they are not required for participation in these projects).

The following Websites give many details of how to arrange for energy saving to be activated on a wide variety of different computer systems:

University of Tasmania: http://www.its.utas.edu.au/documentation/misc/green.text.html

Tufts University: http://www.tufts.edu/tie/tci/pcpowermanagement/FAQ.html

University of Texas at El Paso: http://wattwatchers.utep.edu/pages/PowerManagement.htm

Pennsylvania State University: http://energy.opp.psu.edu/awareness-conservation/computers

The above US Government Department of Energy Website (see http://www.energystar.gov/index.cfm?c=power_mgt.pr_pm_easy_save) also provides free downloadable software, EZ-Save and EZ-Wizard, to enable energy saving on your PC or network of PCs.