Among PC power management means any type of mechanism which is suitable to influence the power consumption of computer workstations. In general, this puts a software hardware in under the given conditions the lowest possible power consumption mode. The PC power management is therefore a portion of the IT energy management.

Hidden energy consumption of PCs

The PC is now in all business areas a common consumer of electrical energy in the workplace. Typically, a PC consumes 90 watts under load ( about 50 watts for the desktop and 40 watts for a typical LCD monitor). The answer is a consumption in the off state of only 3 to 4 watts. Up to 25% of the total energy requirement of a modern office for the supply of constant growing IT infrastructure are required, computer monitors and beat it with almost 40 % of the IT energy consumption to book. Thus the PC power management plays a key role in energy management of buildings.

Recent studies show that in the industrial economy considerable and unnecessary energy losses arise because the user does not shutdown your PC when they leave the workplace. In the UK about. Wasted £ 300 million a year in energy costs and emitted as a direct result of 1.3 million tonnes of CO2. In the United States, where according to studies, 50% of all PCs are annealed overnight, the values ​​are even higher - $ 2.8 billion and 20 million tons of CO2 per year, equivalent to the annual CO2 emissions from Estonia ..

Although, the energy consumption of PCs via low-energy schemes reduce, but there are many situations, particularly in network environments where prevent processes on the computer that the defined settings to take effect. This in turn can have a significant effect on the energy consumption, the user is not consciously perceived. For example, although the monitor is in standby mode and the computer seems to have no activity, has been shown in studies that on average more than 50 % of PCs an organization did not go on any day in the standby mode, long-term concerns that even 90 % of systems.

The actual energy consumption of " shut down " computers is therefore 7.5 times greater than the expected consumption.

" Endurance runner " PC

There are 3 reasons the PC to stop them from going into power saving mode:

  • User activities ( keystrokes or mouse movements )
  • CPU utilization over a defined threshold ( default 20 % of the maximum CPU usage)
  • A process of active requires an operational state of the PC

Additional, more detailed analysis showed that this occurs on different computers at different times of day and night for different reasons:

  • Some computers had defective mice, the movements of the hand -made, so that the operating system thought that the mouse would be permanently moved.
  • Other computers had installed services which were holding the computer by periodically sending an event, the simulated key input from sleeping.
  • Some applications carried out regular internal maintenance from that caused spikes in CPU usage, but it brought no real benefit.
  • Still other applications ( for example, took place music or in presentation mode were ) notified a need for system performance that prevented the computer from going into standby mode. Often this was because the applications had opened a file on the network.


To regulate the problems described and the energy waste associated only through the power settings of the operating system is relatively difficult. For this reason, various manufacturers offer software solutions on the market. The more advanced among them allow network administrators to measure the energy savings achieved or to adjust the power management to the individual needs of the user by automatically wake the computer from standby or backup open documents.

It has been shown that when using this type of energy management tools, an average of 200 kg of CO2 emissions and $ 35 per PC per year can be saved.

The processor of a (office) PCs is generally almost all the time busy to wait for user input. Modern processors then switch to a low power state in which they consume little power, but also provide significantly less computing power; in deep " sleep states " sometimes no more. Once again present work, the processor returns to a "higher" state in order to provide more computing power again.

  • Variant 1: The processor tries to remain in a low state as possible, and to accomplish the task with low power. It lasts for a relatively long time until it is finished.
  • Option 2: "Race - to-idle " ( "Race to Resting ") - The processor switches immediately to the most powerful state to execute the task with the highest power as quickly as possible and as soon as possible fall into a very deep sleep mode again to be able to.

Modern PCs and notebooks generally use race- to-idle, as it is more economical and can carry out the user's job faster. However, if a permanently quiet operation needed (eg no short-time fan whine ), option 1 may be beneficial.

Example for incentives from the policy

With the Carbon Reduction Commitment (CRC ) occur in the United Kingdom from 2010 to various restrictions in force, for the first time force them to actively engage with a lot of companies budgeting of carbon emissions. The organizations have to buy allowances to cover their CO2 emissions. Linked to this are financial incentives for companies that emit relatively little CO2. There are sanctions for particularly high emissions analog.

The CRC used while the energy consumption as a criterion to determine which would fall organization under the new regulations and covers all the national organizations with an energy consumption greater than 6,000 MWh per year from ( the approximate CO2 emissions of an estimated 1280 tons per year of electrical use). The organizations concerned must buy certificates for all CO2 emissions caused. Exception here are all emissions generated by transportation. So to be set by the CRC incentives for efficient use of energy and non-energy sector greenhouse gas emissions are reduced.

As part of the CRC are both made ​​on the supply side measurements to reduce the carbon content of energy consumed depart from coverage measurements to the carbon content is consumed by energy to reduce the CRC is also set incentives for energy efficiency on the demand side. Once fast results are achieved should the attention be directed more and more difficult to realize reductions in energy consumption. Here are included all kinds of energy losses caused by the physical nature of the organization. Is considered also the way how the existing electrical equipment used in the organization.

As state certified energy management tools, the CRC target of 4 million tonnes of saved CO2 emissions could be achieved solely through a focus on the optimization of IT processes by 2020.


  • Energy saving
  • Information Technology