Dark mode can save energy. It can also save nothing. In some cases it can even increase energy consumption. The outcome depends on three factors: the type of screen, the brightness level, and what the user actually does after switching.

Why screen type changes everything

Dark mode only affects energy consumption because of how the screen physically produces light. Different screen technologies respond very differently.

OLED and AMOLED screens (organic light-emitting diode) illuminate each pixel individually. A black pixel on an OLED screen is literally turned off, drawing no power at all. The darker the content, the fewer pixels need to light up, and the less energy the display consumes.

LCD and LED screens work differently. They use a constant backlight that shines through a liquid crystal layer. The backlight is always on at full intensity regardless of what's on the screen. A black pixel on an LCD is created by blocking light, not by turning it off. The energy consumption is virtually identical whether the screen is fully white or fully black.

This means dark mode's energy savings only exist on OLED and AMOLED displays. On LCD screens, which still make up the majority of laptops and many budget phones, dark mode saves effectively nothing in power.

Note
Most laptops sold today still use LCD or LED-backlit LCD displays. OLED laptops are growing fast (up 33% projected for 2026 with Apple's OLED MacBook Pro launch) but still represent a small share of the overall laptop market. On smartphones, OLED adoption has grown significantly since 2017, but many budget devices still ship with LCD screens.

What the research actually shows

The most comprehensive study on dark mode energy savings was conducted by Purdue University and presented at MobiSys 2021. The researchers built a per-frame OLED power profiler to measure real energy consumption across popular Android apps (Google Maps, YouTube, Google News, Calendar, Phone, Calculator) on multiple Pixel and Moto devices.

Their findings contradicted the popular narrative:

At 30 to 50% brightness (where most people keep their screens indoors with auto-brightness on), switching from light mode to dark mode saved only 3 to 9% of total phone power.
At 100% brightness (outdoor conditions or direct sunlight), the savings jumped dramatically to 39 to 47%.
Lowering the brightness itself was far more impactful than switching color schemes. Reducing brightness from 100% to 50% cut OLED power draw by roughly 10x, regardless of whether the content was dark or light.

The widely-cited figure of "up to 63% savings" comes from Google's own testing of Google Maps at maximum brightness on OLED devices. Google's testing of YouTube in dark mode on OLED at moderate brightness showed roughly 15% savings. These numbers are real, but they describe specific apps at specific brightness levels, not typical daily usage.

FYI
Most articles about dark mode sustainability cite the high-end numbers (47%, 63%) without mentioning that these require 100% brightness and specific apps. At typical indoor brightness (30 to 50%), the savings drop to 3 to 9%. That's a meaningful difference when arguing for dark mode as a Green IT strategy.

I wanted this to be short, if this interested you check the full article covering also the "Rebound Effect" and what is it, what this means for the websites and what are the challenges facing the web designers.