This post is also available in: Portuguese (Brazil)
I believe everybody wants to save energy, so I will share some measures that I made years ago with my old CRT monitor 17 inches for different conditions:
(for such measurements, I used a clamp ammeter and I considered power factor equal to 0.80)
Darkening the white background of Windows, we save some watts.
In the same Excel worksheet, I got a reduction of 2W darkening the background of Windows.
Reducing the brightness of the monitor.
Reducing the contrast of the monitor.
Reduction of 14,5W from 100% to 0% in the contrast (fixed bright).
Reducing the refresh rate (Hz)
It is much more comfortable use 75 Hz instead of 60 Hz, despite the increase of 4W.
Activating option of turn the monitor off after a few minutes.
This option will result in a large saved energy. My CRT was set to 3 minutes. In LCD ones, it is recommend to use this option only if you will return back in 15 minutes, at least. Otherwise the process of turning off and turning on repeatedly might reduce its lifetime.
I could see that the contrast has much more influence on consumption than the brightness. However, reducing it, reading becomes more difficult, compared to reduction of brightness. Thus, I recommend you to reduce a lot the brightness; thereafter, you start to reduce the contrast until it is enough.
You must try using the refresh set to 75Hz. It is much better than 60 Hz.
Finally, after a few adjusts, my CRT was consuming 58W, against of 68W (factory settings and Windows default). This is a reduction of 10W without sacrifice.