For the purpose of this discussion, we assume that your PC(s) were supplied with the Windows (tm) Operating System. The greatest opportunity for energy savings will be realized by retaining or resetting the ENERGY STAR default energy saving modes that place the PC and Display in a low power ("sleep" mode) after a period of inactivity. You can make sure that the default ENERGY STAR compliant power management settings are retained or reset through the Windows Power Management control panel. The net savings will vary depending on your use patterns when the PC is in operation. 

You can learn more about savings potential at the following ENERGY STAR official web page:

https://www.energystar.gov/products/computers and https://www.energystar.gov/products/monitors

To save energy with your computer, please be aware of the following:

• Sleep Settings: Set your computer to enter a low power sleep mode when the computer is inactive.  Enabling your ENERGY STAR certified desktop computer's power management features can save your office or home office $15 per year.
• 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 certain types will also keep the CPU from shutting down.
• Games: Many popular computer games left running in the background while multitasking, will not allow the computer to go to sleep - even if the game is paused.

To save energy with your monitor, please be aware of the following:

Activate the sleep settings on your monitor. You can set your monitor to dim first, then enter a low power sleep mode when the computer is inactive.