It’s a decent point. The BBC study points to a write-up on the blog of consultancy firm Valtech of a Purdue study for evidence of those broad claims. The Purdue study puts the savings of dark mode, when using OLED displays with auto-brightness enabled, at between 3–9 percent, and the savings at 100 percent brightness at up to 47 percent.
But how many devices will see that benefit? Research firm Omdia suggested in mid-2024 that OLEDs held 53 percent of the smartphone display market. In 2023, the same firm saw OLEDs as being 14 percent of the combined tablet and laptop market by 2028. So while smaller screens are ready to save some power with black pixels, our larger, more energy-hungry LCD displays are, by and large, not saving much from dark mode and may be just the opposite.
Dark MacBook, dark room, light savings
The BBC’s experiment put 10 people 50 centimeters (1.6 feet) from the BBC Sounds homepage and asked them to alter the brightness until they were comfortable looking at it. Every participant did this adjusting in four variations: dark mode and light mode, and in a dimly lit and brightly lit room. Measuring across 16 brightness levels, the BBC found little difference in power draw between dark and light modes—but, again, this is an LCD screen, so that was expected. The lighting in the room also had very little impact on the brightness level and power draw.
Using dark mode, however, caused the mean brightness level set by the participants to increase from a range of 9.6–10.7 in light mode to 12.5–12.7 in dark mode, with standard deviations around 2.1 for dark mode and 3.2 for light mode. The highest and lowest brightness settings chosen by participants also crept up in dark modes.
The BBC study is just 10 participants, and, as the broadcaster itself notes, calls out for the same study to be done with OLED displays, which have higher contrast ratios and may be easier to read in dark mode at lesser brightness. There are also accessibility and page design considerations not brought into this exercise.
But one website, on one MacBook, hooked up to a power monitor can at least suggest that organic eyes and real computers complicate the conversations around dark mode power savings.
