Saturday, January 20, 2007

Black Pixels are the New Green Pixels

Terrific article from Rising Phoenix Design that points out a rather obvious-when-you-think-about-it fact; black pixels take less energy than white pixels. Background to background, black comes in at about 59 watts, white is at 74, a full 15 watts higher. I'm convinced; the look you see at ecoIron is now permanent. More colors here, and here's a link to Varlath's blog that explains why we changed from black to white in the first place.


slacy said...

This may have been true for CRT displays, but todays modern LCD displays use the same amount of power whether black or white.

Majid said...

very good:)

milkonacar said...


Actually, that's not quite true. For a CRT display, the difference is much high, but there is still a difference for most LCD displays, however small. There are two main consumers of energy in an LCD. One is the backlight (the major component) and the other is the crystal itself, which is activated to either allow or disallow light through the shutter (the minor component). Most sources I've read show black as an inactive crystal, so white requires a small amount of energy to toggle the crystal. An easier (and more readable solution) to the black/white problem is to set the default state of a crystal to open (which allows white to be the lesser consumer of energies).

Matthew Geier said...

I have an old Apple 17" LCD running off a lab supply. (Original supply lost, too expensive to replace).

I have measured it consuming 0.6W LESS when displaying a white screen as apposed to a black one.

I can only assume transmissive is the default state and power is required to hold the crystals in the blocking state.

The main consumer of power is the back light, with the brightness down, the screen consumes less than half the power it does when the brightness is wound fully up.

Fredosaurus said...

As commented above, most of the energy in an LCD display is for the backlight. Matthew Geier's actual measurement of white pixels using less power is typical of modern LCDs which use power to make pixels black.

Earlier LCD screens used more power for white pixels, but the result was a slightly uneven black, so they changed.

Of course CRT, plasma, OLED displays use more power for white.

Epaper (eg, Sony Reader, Kindle) are non-volatile so use no power for either black or white.

WARNING VIRUSES ON THIS BLOG said... has done it.
As of June 16, 2008, they've saved ~666,000 watt hours of energy--and the figure rises by the hour.

Bravo! Green searching = black pixels and now everyone can search ecologically!

Blackle has greened Google.
Imagine how much Google could save if they adopted the black themselves...

I figured out that 661,688 Watt hours = one 60-watt light bulb left on for about 11,028 hours, or 275.7 40-hour work weeks, or 5 ½ years of work-weeks by one person.

Even if the savings are incremental for some LCD monitors, it's a valuable effort--and it can lead, like the ripple effect, to other ideas and actions.

I wonder how they estimate the Watt hours saved?

One of the best, most comprehensive posts on this is here:

Somebody please post the final savings estimates per monitor, whether using LCDs or CRTs, in an easy-to-grasp chart for the general public.