A little while ago, I wrote about remotely turning on console blanking on a Linux machine, and in it I wondered if blanking LCD displays really mattered. The traditional reasons to blank your screen were a combination of CRT burn-in worries and the major power savings to be had from powering down a CRT display; LCDs mostly don't have burn-in, and they have low power usage. But today I realized that there is still a benefit to blanking out your idle LCD displays, or more exactly to getting them into power saving mode.

Standard LCD panels are backlit from a light source; originally this was one or more CCFL fluorescent lights, but these days most displays use white LEDs as the backlight. This backlight is always on if the panel is powered up and displaying any lit pixels at all, and I believe that it's still left on even if the panel is displaying all black (so that when some bit of the display switches to non-black, you don't have to wait for the backlight to come up). When a LCD panel switches to power savings mode, one of the things it does is turn off the backlight.

Turning off the backlight saves some power, which is nice, but it also lengthens the backlight's lifetime. Both CFL and LED backlights eventually dim or fail entirely, and how long this takes depends partly on how long they're on for. This means that powering down the backlight can lengthen the backlight lifetime, especially for panels that won't be in use for a significant amount of time.

(It's probably better for a backlight to stay on than to be toggled off and then back on frequently, but these days many office LCD panels are probably spending weeks or months in power saving mode. Mine certainly are.)

With that said, I don't know how long the lifetime is for typical LCD backlights, and thus how much this matters. Apparently it's common for LCD panels to be rated for 50,000 hours of operation before they fall from full brightness to half brightness, but this can be extended if you don't run your panel at full brightness to start with. If your (work) LCD display already spends half its time off (between evenings, night, and weekends), that's already over ten years.

(And these days many people's home LCD displays are seeing many more hours of usage per week than they were before, while work displays are often getting a nice long break.)