One of the hidden costs in modern life is the growth in small wall mounted power supplies to power everything from telephones to answering machines.

Everybody has boxes of old power adapters too, they have tended to accumulate over time. What is not realized is that most of these cheap adapters is they trend to be very inefficient.

Laptop machines, tape and CD players etc that are in off will draw power from batteries. In the power down state the drain is stopped.

Unfortunately, Windows, by default, does not power down. This has to be done manually.

Desktop personal computers generally used CPU voltage to moderate power consumption. Power supplies, however, are still very inefficient negating the CPU power savings.

StateH-syncV-syncPowerRecovery Time
Stand-byOffOn< 80%~1 Sec.
SuspendOnOff< 30W~5 Sec.
OffOffOff< 8W~20 Sec.

Monitor power savings easier with CRT in standby mode which reduces power consumption by 95%. Desktop machines generally use much less power than CRT monitors. For DOS and Windows DPMS is used by video card to toggle the CRT from standby and active.

Laptop machines have a suspend feature and this mode reduces power to zero. This makes it easier for mobile users who may need to travel from place to place.


The VESA Display Power Management System (DPMS) standard defines 4 states. The signal is handled through the VGA H-sync and V-Sync.

The VESA DPMS power management is supported by DOS, Windows, OS/2 and other operating systems.