Dark Mode - battery consumption.

Howard2k

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Has anyone seen any tests that indicate how much extra battery life is consumed by Dark Mode?


Edit: for clarity, talking about LCD - MacBook range.
 
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solouki

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Hi Howard2K,

Correct me please if I'm wrong, but I believe you should see the greatest battery/energy savings from Dark Mode on OLED displays where the Dark Mode means that less light needs to be emitted by the display itself (the OLEDs, in other words, emit their own light). Contrast this with an LED-backlit LCD display where the LEDs are simply backlighting the display panel, the LCD panel is controlling the amount/color of the light passing through it. For such a display there is little energy savings by having Dark Mode I believe, unless, of course, you also turn down the brightness (LED-backlight intensity) of the display when it is in Dark Mode. If you leave the brightness at the same level, then, assuming that the LEDs are the greatest energy drain on the display, then Dark Mode should not have much effect. I believe the 2018 MBPs use LED-backlit LCD displays ... the latest iPhones/iPads, on the other hand, use OLED displays, so Dark Mode on an iPhone Xs/iPad Pro should have battery/energy saving consequences.

What do you think?
 
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Howard2k

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Contrast this with an LED-backlit LCD display where the LEDs are simply backlighting the display panel, the LCD panel is controlling the amount/color of the light passing through it. For such a display there is little energy savings by having Dark Mode I believe, unless, of course, you also turn down the brightness (LED-backlight intensity) of the display when it is in Dark Mode. If you leave the brightness at the same level, then, assuming that the LEDs are the greatest energy drain on the display, then Dark Mode should not have much effect. I believe the 2018 MBPs use LED-backlit LCD displays ... the latest iPhones/iPads, on the other hand, use OLED displays, so Dark Mode on an iPhone Xs/iPad Pro should have battery/energy saving consequences.

What do you think?
I believe dark mode on LCD would use more power wouldn't it? Not less or the same power.
To darken the pixels (colour vs white) the electrical requirements are increased.

Making those pixels dark would use more power?
At the same time, would it also darken the average amount of light coming from the screen? So to have the same usable "brightness" would you have to have system brightness higher? (more light emitted but then filtered).

I'm not a screen geek, obviously.
 

fisherking

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it seems to me that, in regards to the screen, it's how high the backlight is turned up (that would affect battery life); the backlight doesn't know what's ON the screen (ie a black background, a white one, etc)... it only knows how much it's turned up or down.

so (and someone prove me wrong), it shouldn't make a difference.
 

Howard2k

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it seems to me that, in regards to the screen, it's how high the backlight is turned up (that would affect battery life); the backlight doesn't know what's ON the screen (ie a black background, a white one, etc)... it only knows how much it's turned up or down.

so (and someone prove me wrong), it shouldn't make a difference.
The difference is thst white and non-white are different and non-white uses more power. I’m not sure if there is scaling between colour and power, or what the overall impact is.
 

fisherking

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The difference is thst white and non-white are different and non-white uses more power. I’m not sure if there is scaling between colour and power, or what the overall impact is.
"non-white uses more power"... do you have evidence, of links, to confirm this?
 

Howard2k

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https://superuser.com/questions/483456/does-a-computer-screen-consume-more-power-to-display-black-or-white

lots of discussion online, and opinions. but are there tests to show this? ie running a black background all day vs a white background? there is evidence that it matters on phones (etc) with OLED screens (where, in fact, dark mode offers more battery life).

Exactly the intent of the thread :). It appears to consumes more power in theory. Just wondering if there is any practical testing that anyone has done.

Edit: found this.

[doublepost=1541956474][/doublepost]CF21EB7C-891C-411C-8F77-C30A7E38A422.jpeg https://electronics.stackexchange.com/questions/30541/lcd-led-panel-power-consumption/32018#32018


Dated, obviously.
 
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solouki

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Jan 5, 2017
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Ah! This is very interesting.

Since IPS LCD screens require the thin film transistors to turn on to generate the tiny electric fields to rotate the liquid crystal molecules that rotate the polarized light to allow it to pass through the front polarizer (i.e., become a white pixel), then these transistors in theory would use more power for white pixels than for black pixels.

On the other hand, an LCD screen still gets its light from the LED backlight, and to my knowledge most LCD screens leave the backlight on all the time. I'm no expert, but my suspicion is that the LED backlight generally uses much, much more power than the thin film transistors in the LCD panel, and thus it is really the LED backlighting that primarily affects the battery life of a laptop. This is why if you turn down the brightness of your display then your battery will last considerably longer. (By the way, this is true for both IPS LCD displays as well as OLED displays.)

An OLED display, on the other hand, each pixel generates its own light and thus dark pixels require much less power than light pixels. Thus for an OLED display Dark Mode would indeed save battery life since every dark pixel uses less energy to generate its light than every light pixel. So a predominantly dark screen will require considerably less power than a predominantly light screen.

Having said this, I'm curious as to the actual percentage change in the amount of light being emitted from a Dark Mode screen versus an identical screen set to Light Mode?

And finally, I worry about a crude test comparing two different homepages (Google and Blackle) in a browser at full-screen mode. Who's to say that these two different homepages were running the same JS code, same advertisements, etc? I'd much rather see measurements of the power on a freshly booted machine with nothing else running while comparing a white background image power to a black background image power. This would be a better test in my opinion.

Thanks.
 
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fisherking

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Ah! This is very interesting.

Since IPS LCD screens require the thin film transistors to turn on to generate the tiny electric fields to rotate the liquid crystal molecules that rotate the polarized light to allow it to pass through the front polarizer (i.e., become a white pixel), then these transistors in theory would use more power for white pixels than for black pixels.

On the other hand, an LCD screen still gets its light from the LED backlight, and to my knowledge most LCD screens leave the backlight on all the time. I'm no expert, but my suspicion is that the LED backlight generally uses much, much more power than the thin film transistors in the LCD panel, and thus it is really the LED backlighting that primarily affects the battery life of a laptop. This is why if you turn down the brightness of your display then your battery will last considerably longer. (By the way, this is true for both IPS LCD displays as well as OLED displays.)

An OLED display, on the other hand, each pixel generates its own light and thus dark pixels require much less power than light pixels. Thus for an OLED display Dark Mode would indeed save battery life since every dark pixel uses less energy to generate its light than every light pixel. So a predominantly dark screen will require considerably less power than a predominantly light screen.

Having said this, I'm curious as to the actual percentage change in the amount of light being emitted from a Dark Mode screen versus an identical screen set to Light Mode?

And finally, I worry about a crude test comparing two different homepages (Google and Blackle) in a browser at full-screen mode. Who's to say that these two different homepages were running the same JS code, same advertisements, etc? I'd much rather see measurements of the power on a freshly booted machine with nothing else running while comparing a white background image power to a black background image power. This would be a better test in my opinion.

Thanks.
and we need a number of these tests, for it to really matter. meanwhile, i am now on dark mode on my macbook, and there is no obviously perceivable difference in my battery life at the local coffeebar; am there for an hour or so, and my battery usage is consistent with what it was in light mode. non-scientific observation!
 

alpi123

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There is a test on Youtube with Dark Mode on OLED iPhone. It does improve the battery but at what cost? It's still not perfect if you use apps that have a lot of graphics since it fails to invert some images and I don't know about games or videos. The improvement should be 1-2 hours more at most.
 

fisherking

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There is a test on Youtube with Dark Mode on OLED iPhone. It does improve the battery but at what cost? It's still not perfect if you use apps that have a lot of graphics since it fails to invert some images and I don't know about games or videos. The improvement should be 1-2 hours more at most.
there's lots of discussion about this on an OLED screen; this thread is about what happens on the macbook screen...
 

misterbig

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Aug 19, 2010
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Dark mode shouldn't cause significant decrease in power consumption on Macs since the entire LCD back panel would still need to be lit, whereas on LED screens the pixels are individually turned on/off so a screen that is mostly black would indeed reduce power consumption significantly.
 

Howard2k

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Dark mode shouldn't cause significant decrease in power consumption on Macs since the entire LCD back panel would still need to be lit, whereas on LED screens the pixels are individually turned on/off so a screen that is mostly black would indeed reduce power consumption significantly.

Right. I'm if the increase in power consumption on LCD would be relevant.
 

misterbig

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Aug 19, 2010
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Right. I'm if the increase in power consumption on LCD would be relevant.
It mostly depends on how many nits your screen is set to. If you're using normal mode in a dark room and your screen is only set to 100 nits brightness, the screen will use a lot less energy than if you are outdoors using dark mode but have your screen brightness set to 500 nits.
 

Tech198

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I believe dark mode on LCD would use more power wouldn't it? Not less or the same power.
To darken the pixels (colour vs white) the electrical requirements are increased.

Making those pixels dark would use more power?
At the same time, would it also darken the average amount of light coming from the screen? So to have the same usable "brightness" would you have to have system brightness higher? (more light emitted but then filtered).

I'm not a screen geek, obviously.
Well..its dark, not light mode, so that would assume the color is emitting lower intensity in the display I would of thought. probably not to affect battery that much because what is loss,something else will make up for it (if all things being equal)

eg. you don't enable Bluetooth just because you have Dark mode enabled, or Wi-fi.
 

Howard2k

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Well..its dark, not light mode, so that would assume the color is emitting lower intensity in the display I would of thought. probably not to affect battery that much because what is loss,something else will make up for it (if all things being equal)

eg. you don't enable Bluetooth just because you have Dark mode enabled, or Wi-fi.

Yep, you could assume that, but that's not the way LCD works. Thanks anyway though.
[doublepost=1542115278][/doublepost]
It mostly depends on how many nits your screen is set to. If you're using normal mode in a dark room and your screen is only set to 100 nits brightness, the screen will use a lot less energy than if you are outdoors using dark mode but have your screen brightness set to 500 nits.

For sure.

But all things being equal, I'm looking for the impact of dark mode vs light mode.

Anyway, found something indicative in post #9.
 

fisherking

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you could, ultimately, just use your macbook, and, if you perceive any significant difference in your battery usage, then switch back to light mode.

i use both my macs away from home (one at coffeebars, the other for business), and have not experienced any obvious difference.

just my thoughts, of course.
 

Howard2k

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you could, ultimately, just use your macbook, and, if you perceive any significant difference in your battery usage, then switch back to light mode.

i use both my macs away from home (one at coffeebars, the other for business), and have not experienced any obvious difference.

just my thoughts, of course.

Thanks. And totally agreed, I could just use it.
I don't have to know how my MacBook stores data or what my battery is made of either, but nothing wrong with knowing these things.
 

fisherking

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Thanks. And totally agreed, I could just use it.
I don't have to know how my MacBook stores data or what my battery is made of either, but nothing wrong with knowing these things.
knowledge is always a good thing; but at some point, we can't know it all; how our car works, and the details of the macbook battery... how fish sticks are made, how healthcare in the US works.

too much stuff! so, maybe worth knowing what we need, and learning more when we need it. anyway, enjoy your macbook/mojave/darkmode. (i know i am....)....
 
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