Comments on: Energy-efficient web pages?

Question: Energy-efficient web pages?

molybdenum — Tue, 20 Mar 2007 14:28:22 -0800

Are black-background web pages more energy-efficient?

I recently created a web page whose text is yellow on a black background. Someone asked me why I chose that color scheme, and I replied, jokingly, 'it's energy efficient; it uses fewer pixels!'

I was kidding, but I started wondering if maybe I was right. After all, at least for CRT tubes, I imagine a black pixel is created by the electron gun failing to fire at the phosphors on the screen. Presumably that would use less electricity. Not sure about LCDs, though.

Anyway, is my response (accidentally) true? If Google, for example, changed their page to be white text on a black background, would that save the world an appreciable amount of electricity?

(I realize, of course, that whatever energy would be saved pales in comparison to the power required by datacenter space, and probably a thousand other things. I'm still curious about the answer, though.)

By: cortex

cortex — Tue, 20 Mar 2007 14:38:57 -0800

Here's one bit of napkin math on the subject: black google energy savings.

It's certainly a little bit more energy efficient, for at least some displays, but whether or not that efficiency scales to any meaningful value depends an awful lot on how many people are looking at it, on what percentage of their screen, for how long. The linked article suggests a cost savings of about $75K/yr for Google, which makes me wonder if the average non-ginormous site would even be measurable.

By: borkencode

borkencode — Tue, 20 Mar 2007 14:42:48 -0800

With LCDs the back lights are constantly on, so to get black the LCD needs to become opaque, which I guess would cancel out any energy saved by a CRT not lighting up some phosphors.

By: euphorb

euphorb — Tue, 20 Mar 2007 14:44:32 -0800

Here and here.

By: deadfather

deadfather — Tue, 20 Mar 2007 15:18:06 -0800

LCDs don't use significantly more energy to block light (i.e., make black) than to let it through (make white). LCDs can essentially be taken out of the equation. So black web pages save less and less energy as LCDs become more widely adopted.

By: molybdenum

molybdenum — Tue, 20 Mar 2007 16:18:16 -0800

Thanks for the responses! Kinda disappointing that someone already had my idea. I thought I was being all clever. :(

(Also disappointing that it doesn't help much, but I didn't really expect it to).

By: cmiller

cmiller — Tue, 20 Mar 2007 19:02:47 -0800

(What ever happened to the initiative/idea to get MICROS~1 to set more energy-efficient defaults on copies of Windows? Someone estimated the savings, and it was something-point-21 gigaWatts or something. Pointers anyone?)

By: atbash

atbash — Wed, 21 Mar 2007 15:41:52 -0800

LCDs don't use significantly more energy to block light (i.e., make black) than to let it through (make white). LCDs can essentially be taken out of the equation.

The LCD on my 1400x1050 ThinkPad T41 burns through about 300mW more battery per hour on solid black than on solid white. It's not like the savings between an old Edison bulb and a low-energy fluorescent, but it winds up being about 10 minutes less use that I get out of a 3 hour battery if it's displaying all black rather than all white the whole time.

It should also be noted that the T41 I'm making an example of is getting to be fairly old, and newer LCDs tend to be much brighter and often have more pixels, especially on standalone LCDs. This means that white over black is an even greater energy efficiency on newer LCDs.

By: vytae

vytae — Tue, 24 Jul 2007 14:26:32 -0800

An update: I'm not sure whether it will make a difference, but somebody has implemented the black-background google. Now all they need to do is get everyone to use it, instead of the original. Check it out: blackle.

It occurs to me that you could probably do something with css to set your browser to default to a black background with light text on all websites, if you really, really cared. I still don't see it being worth the effort, though, given the discussion in this thread.