MonitorOffSaver is a cool free screensaver which can save a good amount of energy by turning off your monitor when you are away or system it idle, it will turn off the monitor at the time when screensaver is set to start.
You can easily power off the monitor to save energy and power on it back automatically when your computer resumes back from screensaver, In order to install you just need to copy the screensaver file in C:/Windows ( assuming c drive is where you have your operating system installed )