How much battery does dark mode save?: an accurate OLED display power profiler for modern smartphones

Abstract

By omitting external lighting, OLED display significantly reduces the power draw compared to its predecessor LCD and has gained wide adoption in modern smartphones. The real potential of OLED in saving phone battery drain lies in exploiting app UI color design, i.e., how to design app UI to use pixel colors that result in low OLED display power draw. In this paper, we design and implement an accurate per-frame OLED display power profiler, PFOP, that helps developers to gain insight into the impact of different app UI design on its OLED power draw, and an enhanced Android Battery that helps phone users to understand and manage phone display energy drain, for example, from different app and display configurations such as dark mode and screen brightness. A major challenge in designing both tools is to develop an accurate and robust OLED display power model. We experimentally show that linear-regression-based OLED power models developed in the past decade cannot capture the unique behavior of OLED display hardware in modern smartphones which have a large color space and propose a new piecewise power model that achieves much better modeling accuracy than the prior-art by applying linear regression in each small regions of the vast color space. Using the two tools, we performed to our knowledge the first power saving measurement of the emerging dark mode for a set of popular Google Android apps.