A customer who is currently developing their Green IT policy asked me a similar question recently - and its a great question! So here was my response...
Energy Star compliant monitors need to meet 15 watts or less per hour in sleep/low power mode. They have some good stats on their website about how powering down or low power modes affect computing equipment:
- Computers: A well-designed ENERGY STAR qualified computer will not lose its network connection, which could lead to a loss of data, while in the low-power or sleep mode. Most of the computers that are being manufactured today include a capability to sleep intelligently on a network.
- Monitors: Only after the machine has been used 20 to 30 years will switching it on and off five times or more a day increase the frequency of faults in power transistors in the control and deflection parts.
- Screen Savers: Despite common belief, a screen saver does not save energy. In fact, more often than not, a screen saver will not only draw power for the monitor but will also keep the CPU from shutting down.
So to do an example calculation: if you calculate 15 watts per hour across 1000 monitors = (0.015 kilowatts * 1000 monitors) = 15 kilowatts an hour. This is equivalent to 10 kilograms of carbon dioxide.
You can do the same calculations on the actual computer box - the Energy Star requirement is for consumption of <30 watts per hour in sleep mode. So for 1000 computers it is 20kg of CO2. Add them together & every hour 1000 computers with 1000 monitors are in low power/sleep mode, you are effectively emitting 30kg of carbon.
The equivalent of 30kg of carbon in every-day terms is approximately equal to using 15 litres of petrol in your car.
A few more resources:
- This website is good for equivalency calculations: http://www.epa.gov/cleanenergy/energy-resources/calculator.html
- Next year (TBC) the Australian government will be introducing new standards which ALL computer/monitor manufacturers will be required to meet i.e. a set limits on how many watts a computer & monitor consumes in sleep mode. So while Energy Star is currently optional, the government will soon make it mandatory.
- The Microsoft environment website has lots of general environmental solutions information: www.microsoft.com/environment
- Energy Star has developed a Desired Configuration Management (DCM) Pack for System Center Configuration Manager (SCCM) to help you identify which computers comply with Energy Star requirements: http://www.microsoft.com/environment/campaign_energy_star.aspx. System Center also allows you to use Wake On LAN (WoL) capability to wake up sleeping computers so they can be patched.
- This whitepaper helps you calculate energy savings using Windows Vista: http://www.microsoft.com/whdc/system/pnppwr/powermgmt/VistaEnergyConserv.mspx#