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Power-Saving for £0. Lisa Nelson University of Liverpool. The Problem. Computers often left on all the time, regardless of whether they are in use Changing people’s behaviour is difficult Need an automatic power-saving mechanism. The Goal. Reduce power consumption When PCs are idle

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power saving for 0

Power-Saving for £0

Lisa Nelson

University of Liverpool

the problem
The Problem
  • Computers often left on all the time, regardless of whether they are in use
  • Changing people’s behaviour is difficult
  • Need an automatic power-saving mechanism
the goal
The Goal
  • Reduce power consumption
  • When PCs are idle
  • Without risking losing data
  • At no cost
use built in windows capabilities
Use Built-In Windows Capabilities?
  • Hibernate?
    • Excellent power reduction
    • Can have issues in network environments
  • Standby?
    • Good power reduction
    • Same potential issues with network environments
  • Power down hard disks?
    • In practice, did nothing
  • Stores settings for the current user!
  • No management by policy!
use third party utilities
Use Third-Party Utilities?
  • Cost
  • Client utilities
    • E.g. LocalCooling
    • All limited to underlying Windows capabilities = same problems
  • Centrally-managed utilities
    • Can only schedule = less aggressive
  • Shut down
  • But only when nobody is logged on
  • Not very aggressive, but safe
    • Excellent for walk-up computers
  • Can be done with batch files and freeware utilities for £0
how it works
How It Works
  • Setup batch file:
    • Create a scheduled task to run power-saving batch file (as the System user) after N minutes idle
    • Copy power-saving batch file somewhere local
    • Also copy two freeware utilities
  • Power-saving batch file:
    • Determine whether anybody is logged on
    • If not, shut down
possible problems
Possible Problems
  • Some people may legitimately need to opt out
    • Running grid applications with nobody logged on
    • Acting as a server
    • So supply a discretionary opt-out mechanism
  • Psshutdown flagged as dangerous
  • NOT a problem: erroneously shutting down when somebody is logged on
our results
Our Results
  • No problems
  • Statistics:
    • Shutdowns per day: ~4,500
    • Total computers participating: ~3,500
    • Average daily downtime: 33,350 hours = >1,000,000 hours per month!
    • Average daily MW (assuming 100 W): 3.3 MW
    • Average daily kg CO2 (0.43 kg/kW): 1,400 kg
want to try it

Want to Try It?

E-mail me: lisa.nelson@liverpool.ac.uk

Or go to


  • No reporting
  • Not very flexible
  • Inconvenient to modify after rollout
  • Not very effective for staff-style working patterns
the big limitation
The Big Limitation

What if you want to do more?

powerman overview
PowerMan: Overview
  • Single executable
    • Copy into place and run POWERMAN INSTALL
    • Runs as a service
  • Controlled by group policy
    • Easy to modify
  • Built-in reporting
powerman features
PowerMan: Features
  • Control monitor, disk, computer idle timeouts
  • Actions: log off, stand by, hibernate, power off
  • Specify different actions and timeouts for:
    • When a user is logged on vs. no user
    • Running on AC vs. DC
  • Exceptions (files or processes, Server service)
  • Scheduled wake and shutdown
powerman reporting
PowerMan: Reporting
  • Built-in reporting
  • Easily see overviews or detail down to individual computers
  • Easy to identify your culprits
how we use powerman
How We Use PowerMan
  • Walk-up:
    • Force logoff after 3 hrs idle
    • Hibernate after 10 mins when nobody is logged on
  • Staff:
    • Can choose what to do when idle:
      • When a user is logged on; e.g. stand by after 30 minutes
      • When nobody is logged on; e.g. hibernate after 10 minutes
where we are now
Where We Are Now
  • All our power-saving is now being done by PowerMan
    • Walk-up: <1 hr idle/day
    • Staff:
      • Still in progress – ~2000 computers yet to choose settings
      • But have cut idle time by 25%; anticipate eventually 75%
  • Previously 1,000,000 hrs/month; anticipate eventually 2,000,000
want to try it19

Want to Try It?

E-mail: info@datasynergy.co.uk

Or go to