Go green by going black? …not convinced.

I just came across an interesting post about energy savings based on the colour of a webpage (specifically, Google – but the idea applies everywhere): A black Google start screen? | Wired Gecko.

I’ve found other posts dating back to May of this year (The Numbers Guy) on the subject, so it’s really not a new idea.

The largest part of my doubt is the question of technology. In a CRT, it does indeed use more energy to display bright colours than dark (ref. DOE Energy Star Desktop Information). A CRT produces bright colours by directing an energy beam at the front of the screen; more brightness == more energy used.

As pointed out by Graphics Optimization, the technology in an LCD monitor is entirely different – the brightness is provided by a backlight of some description, and colours are produced by filtering that white backlight with liquid crystals. In this scheme the lowest energy consumption is for a white pixel, where nothing is filtered. Turning a pixel black requires filtering pretty much everything, so uses the most energy.

The DOE report mentioned above appears to have been published in 2001 (curl -I http://www.microtech.doe.gov/EnergyStar/info.htm gives a Last-Modified date of November 27, 2001), when CRTs were far more prevalent than they are today. That said, the CRT isn’t dead – just old, heavy, hot and bulky. If you (like me) do still use CRTs heavily, there are things you can do to reduce your impact:

  • Blackle is a frontend for Google which displays in white-on-black. As of this writing, their homepage claims to have saved 370,654.618 Watt-Hours of energy, versus searching Google directly. Note that in a side-by-side comparison their search results are not identical to Google’s. This is possibly due to their own customizations (the first result for “bob” is about energy savings) or Google tailoring my results when I search google.com directly.
  • User Style Sheets allow you to override the display of some/all pages you visit. The method is different for each browser, but here are a couple starting points:
    • Firefox lets you set these overrides in your userContent.css file.
    • Safari allows you to set your user stylesheet from the Advanced Preferences pane, or you can install SafariStand, which allows you to set specific stylesheets for individual domains (bonus: this allows you to override the nasty serif fonts used on NYTimes.com and a few other newspapers!)
  • OS-Level Accessibility Settings often provide options for white-on-black or other high-contrast display modes which will affect your entire system.