One of the significant features Microsoft introduced in Vista is new power saving mode. Windows XP has two power saving mode, Standby and Hibernate. Windows Vista replaced them by Sleep mode. Hibernate is still available as an advanced power setting, but the Sleep mode is the default one and has more advanced features.



While in sleep, computer uses very less power for internal use. In notebooks, with the minimum power used during sleep mode, system goes to stand by mode and the state of the system is saved in the memory. If battery power goes down to critically low level, the system wakes for a very short time to save the needed information onto the hard drive, and immediately goes to hibernate state.

In Desktop systems, the process is little different. Here Microsoft Vista uses "hybrid sleep". In hybrid sleep, the state of the system is stored both in RAM and on disk, so that system can recover it's state in case the power is lost. After saving the state of the system, it goes to sleep mode from where computer can easily bring back to working state. Top goal of introducing this mode is enabling easy and first ?on? and ?off? of the computer. While making sure computer can save all data when the system is turned off, and brings in same state while you turn back on. In order to ensure that "off" worked effectively with this new model, instead of waiting for green signal from each application in the computer, Windows Vista sending notice to each application, services and devices about the power saving state and wait for maximum 2 seconds for them to finish up their current job and put themselves into a state from where they can continue when the system wakes up. Similarly Windows vista is very fast to come back from the sleep state. When you open the lid of your laptop, you will find your system becomes instantly on, sometime you may wonder if it was on whole time.

Another goal is to reduce the power consumption when the system is idle. Normally we want to avoid long boot process of the computer, so we prefer to keep the system up 24X7. This may be nice to keep your system always ready to work but in this way we are wasting huge amount of power. Windows Vista's sleep mode made dramatic change to reduce computer's idle power consumption. While a typical Pentium 4 system uses 102.6 watts of power, same PC while in sleep consumes only 5.6 watts. Vista provides API for the application developers so that application can get notifications about the power scheme being used on the system and then adapt their behavior for the power scheme.

Using Microsoft group policy IT administrator of a Business organization can decide that all machines will go to sleep after specified time of inactivity. Normally in large organization tons of computers sitting idle and because of that huge power gets wasted. This feature must help them to reduce power wastage.