TL;DR — Yes, and a little bit.
A zillion years ago I was shown blackle.com
, it's google, but with a black background.
Blackle
was a black page with a google search bar. It swapped the bright white background of google
with total black. Supposedly this saved a lot of electricity. Dark pixels used less energy than bright ones.
So, we all changed our homepage to blackle
and saved the planet. Actually, the fad of using blackle
ended as fast as it started. We found out that blackle
had no impact on our screens' energy use and forgot all about it.
Low Impact Manifesto — article 9
The other day someone sent me a link to the Organic Basics - Low Impact Website. It's an e-commerce site designed to minimize environmental harm.
The code is open source, and comes with a manifesto describing 10 things a Low Impact site should do.
Number nine says a low impact site "Limits the amount of light emitted by the screen." I remembered blackle
and how it had turned to be a disappointment. But the people who built this site did their research, I should do mine. So I got to googling (blackling?)
CRT vs LCD vs OLED
It was around 2007-08 when i first saw blackle.com
and most screens were liquid crystal displays
.
LCD
LCD
screens are illuminated with a backlight. The liquid crystals change color, but can't emit light themselves. The backlight is on no matter what the screen is displaying.
No matter how bright a pixel is the energy consumption doesn't change. So a site like blackle
has no impact on power consumption.
CRT
When blackle
first launched in 2002 the majority of screens were Cathode-ray Tubes
.
CRTs
do use less electricity when the screen is black. CRTs
also use a lot more electricity than LCDs
. So blackle
really did make sense.
OLED
Today LCD
is still the most popular but will soon be overtaken by OLED
. OLED
screens are made up of pixels that emit light independently of each other. What's more, the power consumption directly correlates with the brightness of each pixel. So the less bright a pixel, the less electricity is used.
Using a site like blackle
, or setting your phone to dark mode
really does save power. But how much?
How much energy does dark mode save?
Mobile Enerlytics is a company that measures the energy use of phones. They did some experiments and concluded that dark mode
saves a lot of battery life. Between 5.6%
to 44.7%
on a device at full brightness and 1.8%
to 23.5%
at 38%
brightness.
The big differences in percentage of energy-use depends on the activity of the phone. A cpu
heavy task, like watching a video, uses a lot of energy, so comparatively less energy is used by the display. For simpler tasks, like reading an article, dark mode
results in much longer battery life.
So, dark mode
does significantly improve battery life. But how much energy is being saved? And how does that translate to CO2
?
Back of envelope calculation
I've no idea how to find an accurate answer to this. But rough calculation should put things in perspective. We'll use the iPhone X specs as a guide.
The iPhone X
uses a 20 watt
charger and takes ~1 hour
to charge. If you charge it fully once per day, that's 20 watt hours
a day, 7.2 kilowatt hours
a year.
In the USA 0.4kg
of CO2
is emitted per KWh
. Let's assume we're saving only 5%
using dark mode
. So 1 million
iPhone X
s on dark mode
for a year would save about 144,000kg
. The same as 31 cars.
1 Million iPhone X's on dark mode ≈ 31 Cars
There are more than 200 million
cars in the USA. So, I'll let you decide if dark mode
is worth thinking about as solution to the climate crisis.
Personally, I think small gains like this add up. The climate crisis is a complex issue. Every source of C02
can be broken down to smaller and smaller parts. Eventually issues like this need to be solved. Luckily for us, Dark mode
will happen on its own.
Dark mode
isn't about saving the planet. It's about usability and to a lesser extent battery life.
As dark mode
gets more popular, consumers will expect it from apps and websites. The environmental gains will come for free.
Top comments (2)
Don't be tempted by the dark side, padwan!
Well, dark mode and energy savings... I just don't see it to be honest. There are way more impactful ways out there to save energy. However, the long-term impact of using dark mode for human eyes - that is something I'd be interested in.