Monday, August 06, 2007

The Full Story on Black Google, Blackle, etc.

Here's a Wiki-esque post that covers the full story on Black Google, I'm working on the Wikipedia entry but it's taking some time.


In January 2007, Mark Ontkush, the owner of the ecoIron blog, suggested that a large amount of energy could be saved if Google switched their home page from white to black. The initial savings was estimated to be 3000 Megawatt-hours a year; this was later rounded down to 750 Megawatt-hours, after an error in the calculations was found. At the time, ecoIron was receiving about 100 hits per day. The story was posted on Digg where it rapidly went to #1 on the main page, ultimately receiving over 4,000 Diggs. Tony Heap, the owner of HeapMedia, started the Blackle site shortly after these events.

Appearance and Functionality

The Blackle site uses the Google search engine and works in much the same way; users enter text into the box provided, and the query is sent to the Google search engine. The searches both use the same searching algorithm and are executed on the same hardware. However, it has been suggested that the result lists might differ. Blackle uses light grey text on a black background; this is in lieu of the customary Google layout of blue, black, and green text on a white background. Since it is not owned by Google Inc., the Blackle site lacks many of the features of conventional Google, including the 'Cached' and 'Similar Pages' options, and it does not have as many of the corresponding links that can be found on the Google homepage. These links include items such as preferences, advanced search, language tools, images, groups, news and scholar. None of the Blackle links have a visited option, where once a link is followed it turns a different color. The iGoogle feature is also lacking in Blackle.

Energy Savings

The principle is based on the the fact that different colors consume different amounts of energy on computer monitors. Depending on the manufacturing technology, and to a lesser degree the brand of the manufacturer, these colors and energy levels vary. An explanation is provided below.

Cathode Ray Tube (CRT) Monitors

A CRT monitor uses a cathode ray tube to display images. The back of the tube has a negatively charged cathode, and an electron gun shoots electrons down the tube and onto a charged screen. The screen is coated with a pattern of dots that glow when struck by the electron stream. Each cluster of three dots, one of each color, is one pixel. Certain colors, such as white, require all three dots to be charged, and are energy intensive to display. Other colors, such as black, requires no additional energy to produce and consume the least out of all the colors.

Therefore, power consumption for CRT monitors is primarily a function of the user's color settings and desktop graphics, and any given CRT monitor requires more power to display a light screen than a dark one. Other authors, such as Roberson et. al., have verified these results. The amount of energy saved from switching from white to black varies considerably on the size of the monitor. In a 2002 study, Roberson found that between 4 and 30W could be saved by switching from a white to a black screen. This translates into an 18 to 88% power savings per monitor. The US Department of Energy produced similar results, stating an average 15W savings per monitor. Several informal studies have also been done, with results ranging from a 7 to 23W reduction when using a black screen.

In the first quarter of 2006, Display Search, an industry reporting service, estimated that CRT monitors comprise 25.3% of all monitors in the world. There are substantial regional variations; for example, the report mentions that as of 2006, 45.3% of the monitors in China, and 62.8% in Latin America, were still CRTs.

Liquid Crystal Display (LCD) Monitors

A liquid crystal display (commonly abbreviated LCD) is a thin, flat display device. LCD monitor are suitable for many types of devices, including computer monitors and battery-powered electronic devices. Unlike CRT monitors, LCDs rely on a constant source of illumination, commonly known as a backlight. Backlights produce light in a manner similar to a CRT display, with the difference that the backlight is always on. Backlights can be any color; monochrome LCDs usually have yellow, green, blue or white backlights, while color displays use white backlights that cover most of the color spectrum.

A pixel in an LCD display typically consists of a layer of molecules aligned between two transparent electrodes. When a voltage is applied across the electrodes, a torque acts to align the liquid crystal molecules parallel to the electric field. This reduces the light shining through from the backlight, and the device appears gray. If the applied voltage is large enough, the liquid crystal molecules are completely untwisted; the results is that the backlight will then be completely blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, light can be allowed to pass through in varying amounts, correspondingly illuminating the pixel.

As such, LCD display technology is different from CRT technology, and the possibility exists that colors that are energy efficient to display on a CRT monitor (e.g. black) may not be as energy efficient to display on an LCD monitor. The Roberson study found that LCD monitors saved up to 3W by switching from a white to a black screen, and in no case did any of the LCD monitors use more energy displaying black than white. Recently, several informal studies have been done, with results ranging from a 2W reduction when displaying Blackle vs Google on an IBM Thinkvision LCD, to zero, up to a 1W increase.

Display Search estimated in Q12006 that LCD monitors have 74.7% penetration rate worldwide. Japan is the country with the highest rate; 99.3% of their monitors use LCD technology.

Plasma Displays

A plasma display panel (PDP) is a type of flat panel display commonly used for large TV displays, typically above 37" (940 mm). Many tiny cells located between two panels of glass hold an inert mixture of noble gases (neon, which are contained in hundreds of thousands of tiny cells positioned between two plates of glass. electrodes are sandwiched between the glass plates, in front of and behind the cells. Control circuitry charges the electrodes that cross paths at a cell, creating a voltage difference between front and back and causing the gas to ionize and form a plasma; as the gas ions rush to the electrodes and collide, photons are emitted. To erase a cell, all voltage is removed from a pair of electrodes.Every pixel is made up of three separate subpixel cells, each with different colored phosphors. One subpixel has a red light phosphor, one subpixel has a green light phosphor and one subpixel has a blue light phosphor. These colors blend together to create the overall color of the pixel. Plasma displays use the same phosphors as CRTs, and are bright, 1000 lux or higher being the norm.

Plasma displays use as much power per square meter as a CRT, and consumption varies greatly
depending on what is watched on it. Bright scenes (say a football game) will draw significantly more power than darker scenes (say a movie scene at night). Nominal measurements indicate 400 watts for a 50" screen.

Currently, plasma displays are not popular for computer monitors. However, since they operate similarly to CRT technology, the energy differentials are similar. A study conducted by G4TechTV using a Samsung 42" plasma display found a 191W differential for a white vs. black screen in normal mode, and a 138W differential in super energy savings mode. Plasma displays are particularly well suited for the large displays, outpacing other types of display technologies. However, recent improvements in LCD technology have contributed to falling prices, higher resolutions, and often lower electrical power consumption, making them very competitive against plasma displays.

As of late 2006, analysts note that LCDs are overtaking plasmas, particularly in the important 40" (1.0 m) and above segment where plasma had previously enjoyed strong dominance a couple of years before.


An organic light-emitting diode (OLED) is any light-emitting diode (LED) whose emissive electroluminescent layer comprises a film of organic compounds. The layer usually contains a polymerpixels can emit light of different colors. substance that allows suitable organic compounds to be deposited. They are deposited in rows and columns onto a flat carrier by a simple "printing" process. The resulting matrix of OLEDs are used in television screens and computer displays; a great benefitof OLED displays over traditional liquid crystal displays (LCDs) is that OLEDs do not require a backlight to function. Thus they draw far less power and, when powered from a battery, can operate longer on the same charge. No comprehensive studies have been conducted of a comparison a white vs. black screens, but due to the nature of their construction, it is probable that displaying white
consumes more energy than black on a OLED device.


The effectiveness of using the 'black web' technique to save energy is a subject of intense debate, much of which centers on the pros and cons of a specific implementation, and the scale at which the approach is implemented. Other discussions are focused on the amount of energy saved, both individually and collectively, and the trade-offs involved in implementing a solution of this type. A summary of the different approaches is provided below.

Governmental/Corporate Policy

One approach is to modify a color scheme of incoming web traffic at a high level, such as the corporate or country level. In this case, an entity with a large number of CRT monitors might intervene on their users' behalf to convert the color codes as they travel through the network, thereby producing a uniform color scheme for the entity as a whole. To date, there have been no reported implementations of this strategy. However, countries such as China or Brazil, who demonstrably have a large number of CRT monitors could save significant energy.

Single Site

This approach relies on a particular web site to change their primary color scheme; the net energy savings or loss can then be calculated by estimating four parameters:

  • The amount of traffic the site gets.
  • How long a visitor remains on that site.
  • Percentage split of CRT/LCD monitors in worldwide use.
  • The differential of how much energy is drawn by each monitor type in each color state.

Any site can be used; Google is often cited due to the sheer amount of traffic the site receives, but other sites such as Yahoo, MySpace, or YouTube could be analyzed as well. Ontkush took this approach in the original post, and used Google as an example. He used the following parameters:
  • 200 million queries/day.
  • 10 seconds/query.
  • Monitor split of 25% CRT, 75% LCD.
  • CRTs received a 15W differential from white to black,
    LCDs received no differential.

Using these parameters resulted in a net energy savings of 750 megawatt-hours per year.

Much of the controversy in using the this approach revolves around modifying one of more of the parameters, particularly the energy differentials and CRT/LCD ratio. However, even using generous, apocryphal numbers for these parameters still results in a net energy savings. For example, if one assumes a 10% CRT, 90% LCD ratio, and substitutes a 10W differential for CRTs and a -1W differential for LCDs, implementing the technique still saves energy; the large energy differential for CRTs overwhelms their market share. This, when multiplied by a tremendous amount of display time, produces the savings.

In July 2007, the Financial Times reported that, according to the Nielsen/NetRatings for May, users spent 2,557,000,000 minutes on Google websites; this translates into 511,400,000 hours of Google website use per year. The monthly figures for Yahoo (746M) , MySpace (7,535M), and YouTube
(2,117M) are comparable.

Using a Proxy Site

Another approach is to use a third party site to implement some functionality of an existing site, and then use an alternative color scheme. This is the approach used by Blackle and similar sites to mimic
the Google site. In this case, users must deliberately use the alternative site instead of Google's home page.

Using this approach, the savings in energy is directly related to the type of monitor that the individual is using at the time, and how often they frequent the site. As indicated, if one is using a CRT, Plasma, or OLED monitor, energy savings will certainly be accrued. However, for LCD monitors the results are not so clear; studies have shown that LCD monitors either save or use a small amount of energy displaying a black page as compared to a white one, so the energy savings would
be much smaller or, worse, the monitor could use more energy on the modified site.

Individual Efforts

A third approach is to use a script or browser option to alter the color scheme for some or all the pages one views. Again, this approach requires user intervention, and is subject to the type of monitor that the individual is using to view the pages. The advantage to this approach is that significant energy savings can be realized, as all incoming web traffic is converted to a low-energy format. There are several alternatives depending on the browser and/or operating system in use.

Users of the Firefox web browser can install a GreaseMonkey script called Google Dark which will automatically reverse their color scheme when visiting the authentic Google site. For a more generic approach, one can go to 'Tools > Options > Content > Fonts & Colours > Colours' in Firefox and change the default color background and text to any desired color; users who implement this option should uncheck the box that says "Allow pages to choose their own colors, instead of my selections above".

Internet Explorer

In Internet Explorer, go to 'Tools > Internet Options > General > Appearance > Colors' to alter your personal color scheme. You will also need to go to 'Tools > Internet Options > General > Appearance > Accessibility' to override the default color options on the pages that you visit.


There has been both praise and criticism for this initiative, with its supporters citing it as a great example of environmental thinking, and its detractors pointing out usability and aesthetic problems, as well as questions about the scientific validity of the claims. Some of the issues are listed below.

  • Since the technique is most effective on CRT monitors, some proxy sites have been criticized for not mentioning this fact. In particular, the Blackle site has been heavily criticized, as it is probable that they are generating an substantial Adsense revenue stream from implementing the concept.
  • CRT monitors are being phased out; about 75% of monitors in active use worldwide are LCDs. Additionally, countries with a high percentage of CRT are replacing them rapidly; for example, Display Search projects that only 18% of the monitors in China will be CRTs by the end of 2007. Therefore, although the technique would be effective for a limited period, it is questionable whether the disruption
    would be beneficial.
  • CRTs are generally darker than LCDs, and the text on many of the proxy sites is barely readable on monitors of this type. For example, Blackle uses a small grey font on an all black background. It is possible that these 'all black' proxy sites are only usable on LCD screens, and this would
    negate the energy savings.
  • Proxy sites cannot handle the heavy load that high volume sites are accustomed to. For example, on August 1st, 2007 and several prior occasions, the Blackle web server was producing intermittent error messages for extended periods of time.

Alternative sites


Unknown said...

A true tour-de-force, Mark. One of the reasons I have kept reading Ecoiron all these months is that I am always learning something new (and useful) from it. Actually, it was with that in mind that I nominated Ecoiron for a Blogging for Positive Global Change award. Not that you really seem to need the recognition and kudos, but I believe in giving credit where it's due.
Best Regards, Keith

Unknown said...

This article is an eye opener to sites such as 'BLACKLE' i never knew that Blackle only save energy for CRT computers and worse....

Quote: 'studies have shown that LCD monitors either save or use a small amount of energy displaying a black page as compared to a white one, so the energy savings would be much smaller or, worse, the monitor could "use more energy on the modified site."

I think Blackle should post it on their 'About BLackle' page. As i have already set my homepage to BALCKLE and realised after reading the article, that my LCD computer does not save energy by doing that!

Predrag Stojadinovic said...

Great article. In my opinion it doesn't really matter how and if this whole idea is true. In other words, it may and may not save energy on this or that type of monitors. But, what is really great about this article is the actual honest attempt to save energy as well as the awareness it raises about the whole issue. Great job, now I know what was the little voice in my head that told me to build my site black :D
Preferans Online
Keep up the good work,

Alison Cross said...

Thank you so much for taking the time to pull all this information together. I have learned a great deal!

I have an LCD monitor and realise that the energy savings are negligible, but was wondering whether there was more that I could do? EG - setting my screensaver to black, altering my settings so that my Word documents are white font on black background. Would this help or is it not worth the hassle? Anyone?

james Shack said...

Mark mentioned that Blackle site lacks many of the features of conventional Google, including the 'Cached' and 'Similar Pages' options. However Darkoogle and Blackgoogle does provide 'Similar Pages' options, especially Darkoogle with search by country which make their search results more relevant.

Bill said...

I posted this on the original article (and we've gotten some good traffic from it!), but thought I'd repost as this seems more active:

A charity I work with has created a site that lets people choose the colors of their Google Search right in the URL, and I have now created an Emergy-C pallete that they can use very simply.

The site is

100% of all proceeds from the site go to the Hypoplastic Right Hearts organization, which is a fabulous group who helps children congenital heart disease and their families.

As you can see on the page, you can actually put any colors you want in the URL, such as:
or (foreground.background):
or even hex codes, such as:

I hope this helps your readers and that you'll promote this, as it not only lets your users save energy, it also helps support a great cause.


abby said...

this is brilliant information, promoting the use of Blackle from the original treehugger bit as part of my job as Environmental awareness officer, but did not know that it only works on CRT screens, will make sure that people know this in the future. Also other sites that offer country by country searches will be invaluable, a feature that would have been useful on the Blackle site. Little steps like this are vital but remember we need big steps too.

Unknown said...
This comment has been removed by the author.
Unknown said...

I think despite the criticisms and the arguments against using black or darker backgrounds, it still is a great idea of trying to help the environment every little way we can.
A lot of sites have followed Blackle and started using the same concept even if there are arguments against it.
The site that I particularly like that isn't on your list is Greenback Search at The site's motto is to give some green back. It uses the eco-friendly darker colors but more importantly it purchases carbon offsets on behalf of users when searches earn revenue. The site also has some nice tips and information on the environment that can be helpful.
I think it can be a good alternative to Google since their search site is powered by Google. Check it out for yourselves.

webperc said...

I must agree that Blackle's idea is admirable, but it seems like they did not do their homework.

My thought is to plainly reduce the time using the entire computer. How?

My strategy is to experiment with effective search tools that can significantly reduce my time spent wading through mountains of search results.

I have created several Google Custom Search Engines using Google's Topic Driven Search Technology to group results.

Entering an initial search string in the search box and hitting the search button displays a list of topics below the search box. When you select a topic my search combines the previous search string with the search string I have placed inside the topic.

It works quite well and reduces the time you spend running searches.

I have three main custom search engines that I have created. The Plasma TV Custom Search makes extensive use of topics.

Plasma TV Custom Search:
Music Custom Search:
Google Search:

Take a look and let me know what you think.

Ray Szasz

domainism said...

Very informative and very thought provoking - to the extent that if a dark screen is not reliable what else can be done?

If you want to search greener then potentially saving energy with a black screen is a start. The next step is to use the financial spin-off (ie revenue made from Adsense) to offset emissions in general.

Hence - black screen to reduce emissions, and offsets purchased from the money generated. Please try it: free and non-profit:

Gregory said...

End of debate. Think big. When everyone switches to black backgrounds the savings will be enormous. As a designer who has won the International Association of Web Masters and Designers Golden Web award four times for I can assure you that black backgrounds when done with gold and red accents are vaatly superior to white backgrounds. I am also on the voting committee for IAWMD. And although I've yet to officially vote on a site I will vote to give Blackle the platinum web award.

I have been designing in black since 1997 and my first site is viewable at

My name is Gregory GOrDon and I am best known for my political activism in having threatened to kill both Reagan when I broke into his house and Bush in a speech in Philadelphia as they are and were both anti-Christ.

But a little known fact about me is that I have a Bachelor of Science Degree in International Environmental Studies - Public Policy Analysis from Cook College of Rutgers University, 1980.

Sooner or later perhaps when all the fossil fuels are used up which will be in about 50 years we will have no choice other than to conserve every watt of energy to stretch our resources. At any rate doing so will be good public policy.

It is enevitable that black backgrounds will become mandatory. Mark my words. You heard it here first. is now the new Black and I urge all of you to get a piece of the Rock. Do your shopping at and help save the Environment.

Rick said...

One doesn't need to guess as to whether their personal implementation of a black background is beneficial or not. Just buy an inexpensive Kill-a-Watt meter so you can actually measure the difference.

You can find it for less.

And if you use a browser like Opera you can actually toggle the view between black on white, white on black, or back to the original colors.

Once you finish using the Kill-a-Watt meter for this purpose you can audit the rest of your household devices that plug into a 120V outlet.

Sanjay John Gandhi said...

Blackle is just the first page of which has offered google search in color since much longer.

I think black doesn't save much energy-and google officially said that in their blog somewhere-but it is good to have a more colorful internet search experience.


James Purple said...

This post is very interesting.

This video shows how much power an LCD screen needs to display the black background:

I prefer using Greenle.

admin said...

There is also the Carbon Neutral Search Engine, they offset each search by 100g of CO2 ... (or black background for CRT monitors), so not only do you save energy, you also help reduce CO2 emissions.

Unknown said...

I prefer to use another web called blackoogle

Is the same as blackle but with much more functionalities as images, maps, youtube, mail.




dimis said...

the best black google in greek is

Deux Anges said...

Not sure if this the best place to mention this, but here goes:

I changed over to Blackoogle early this year and although suitable for most purposes, I have found its functionality a little limited compared to the original Google. Firstly, it does not include a link for cached versions of the hits. Secondly the links to the image and map searches is disabled.
Very inconvenient!

Unknown said...

There's also the question of whether storing the number for a white pixel ( in RAM ) uses more energy than storing the binary for a black one . . .

I pointed this out a few years ago in an answer to a reader's question . . . here

Shop Advent Green said...

Hello Mark,

Can I reference your blog in my website, as I believe it is a convincing reason to alter background colors to save energy.


Mark Ontkush said...

Can I reference your blog in my website, as I believe it is a convincing reason to alter background colors to save energy.


Unknown said...

The concept is good; however, I checked out a few of the sites and found them hard to read. Even the white on green is very tiring on the eyes.

I don't need to use glasses except for very small print.

I have seen fancy packaging and test on cds that could not be read by many even wearing glasses.

I think that this may discourage people from coming to site or blog. Also for those interested in the content, may print it instead of trying to read it online.

If you are going to consider using this method, make sure that multiple generations read your content on multiple moniters using all major browsers.

Unknown said...

There's also another page, it's called It's owned by google and uses the same way to search, but it can't search for images

I think this blog is great!