OLED Hack Saves Juice On Nexus One

Want to really stretch the battery life on your phone? If you have an OLED display [Jeff Sharkey] may have the answer. He did some testing with his Nexus One to see if color alterations can save on current. Darker colors draw less amperage and he found that the red pixels are the most efficient. He did a little work with SurfaceFlinger, which handles the display on Android devices to make this easy, but what will you get by going red? He measured that using only the red pixels dropped the current use down to 35% of what the full color display was pulling. This reminds us of those efforts to save energy by running a black background with Google. Whether you use it or not his post is an interesting read.

35 thoughts on “OLED Hack Saves Juice On Nexus One

  1. I’d like to see a modified driver that will slowly get more and more “red” (lowering the power on each other color proportionally) as the battery drops.

    If you started at 20% and went full red at 10%, then it would act as a cool way of warning you your battery is low while saving power at the same time.

  2. John Burton:

    LCD screens draw about the same power whether it’s a dark screen or fully white. The same can be said for “LED” screens that still use LCD technology, but just have a different type of backlighting.

    OLED is a different technology, so therefore this IS new.

    1. LCD screens draw less power on a white screen. CRT’s use additive light to build color, so white is considered the most energy consuming color. On LCD’s, light is filtered, so turning a pixel off reveals the white backlight. It doesn’t save that much energy as compared to CRT’s, but each pixel requires a certain amount of uA to be in an ON state.
      The backlight itself is the energy consuming factor. It’s always on. OLED’s are power efficient because you can control backlight to each pixel, since each pixel is a light source, similar to CRT technology.

  3. Great find! I don’t think I would use it as I want my phone to be at it’s most optimal setting instead of bare minimum. It would be helpful if it was on super low battery and I needed to make a call with no charger in sight.

  4. You should check out data sheets and implementation guides for these OLED displays sometime. Red is indeed the most efficient but green has the longest lifespan (blue should be avoided). You would realize an even greater power savings by switching all the backgrounds to black.

  5. @John Burton
    It’s “news” because the relationship doesn’t hold with the majority of displays currently in use (LCDs). LCD power consumption difference is negligible regardless of the image shown, including black.

  6. to: ???

    “It would be helpful if it was on super low battery and I needed to make a call with no charger in sight.”

    good intention, but the screen goes off when you are in a call, right? hey! i guess to save the most battery from the screen, turn it off!! ;)

  7. Wouldn’t a black desktop work best? Or better yet a filter that turns everything on the phone into wire frame using edge detection. That and/or a very short idle time until the screen turns off. Red seems like a stupid compromise where you lose quality images and don’t really save a lot of battery. If you wanted a mono color screen, then you should get an old nokia brick phone with a week long battery life.

  8. @Gene and John Burton

    Not only that, but what is fascinating is the actual numbers that came out of the experiment. For OLEDs the idea of turning off pixels or using only 1/3rd of the pixels (red only) may be kind of obvious to those who know how the technology works, but that there’s a 21% difference in powersaving between blue and red pixels is quite interesting.

    One thing I did notice though is his background has a very blue theme to it. I wonder how much the numbers would change if he used a white background. Even in the pictures above the green setting looks brighter than the red setting (check top right corner of the phone), and my guess is blue even more so.

  9. I do believe that I remember my photonics professor telling me that red is the easiest color to produce. And requires the least amount of energy. Kind of like lasers… makes sense.

  10. At least HAD is doing it’s bit to save energy :)

    Oh, and “amperage” isn’t a word. Neither is “voltage” or “ampage”, but voltage at least is now accepted in some dictionaries due to it entering common use. It’s easier than saying “potential difference” I suppose.

  11. Rather than make wild speculations based off of supposed knowledge, I did a bit of my own testing with Black Google.

    Sure, it cut the power usage considerably with a CRT, which is good, and I suppose his math is right there.
    However, with a LCD, it increased the power consumption. Not by a lot, but it definitely used more power. The same was true for just about any dark screen. This is because an LCD screen works the opposite way from an OLED screen or CRT. The entire screen is always backlit fully, and then pixels block out some of the light, when activated. Where in an OLED screen or CRT, it only activates the pixels it needs.

  12. Wow, I would surely do that to save energy on a phone.

    Bonus points for retaining night vision by using only red lighting.

    And Amperage is not Current (Current is Amperage multiplied by voltage, it is expressed in Watts)

    4 amps at 12 volts is 48 watts.

    4 amps at 120 volts is 480 watts, get it?

  13. If you display red-ish image a lot, the red subpixel’s lifetime will decay faster. So when you wish to see white image, you’ll see cyan-ish(green + blue) image.

  14. @Garbz
    Green may look brighter because our eyes see the green light better.
    A green screen with less brightness but perceived more could be saving more power then a red screen with more brightness but perceived less ?

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