Power efficiency: These are the most frugal smartphones currently on the market

With most smartphones now offering all-around performance above the sanitary minimum, it's only natural that the next enemy to be conquered is battery life. And indeed, our data indicates that more and more of you ask questions relating to the battery of their next purchase before committing. Naturally, our battery benchmark's popularity is at an all-time high.

There are a lot of factors affecting the battery life of every smartphone that goes through our custom test, however, including the underlying technology of the display, the number of pixels on it, its size, along with the processor powering the device, the software, and so on and so forth. Yet, the general populace seems to consider a larger battery as necessarily superior to a smaller one, and that's just a wrong way to think about the problem. Instead, the argument should be centered on power efficiency, not just size, as we've already seen some devices offer some truly mind-blowing endurance, even though their battery has an average capacity (Sony Xperia Z3 Compact, #high-five). Of course, all things being equal, more is always going to mean longer battery life.

We think a lot about this type of stuff, and lately we've been asking a lot of "What if..." questions. Some of you will, naturally, disregard them as pointless, yet thought experiments such as that have their utility. For example, what if the battery in your smartphone was as big as the battery in every other smartphone? Would it perform better or worse than this or that device? Questions of efficiency, in other words. Meaningful questions.

So we sat down and did some elementary calculations using the scores popular flagship devices achieved in our custom battery life benchmark. Using them, we were able to derive a figure that tells us how many seconds of battery life every 1 mAh gives us. From there, it's only a matter of time to work out scenarios with differing capacities — in our case we chose 3,500 mAh and 1,810 mAh. Why these two values? They're two extremes — especially the latter, which is not at all coincidentally the cell capacity of the iPhone 6. Yep, the iPhone 6 does rather poorly in our battery life benchmark, but our data shows that the iDevice is one of the more efficient on the market. Of course, as you can see for yourself, it is outdone by a number of Android devices.

Again, as mentioned, a number of factors combine for the flagships above to produce these scores, including the size of the display and resolution (all things being equal, a bigger display/higher resolution will always mean the device is worse off in terms of battery life), processors, and software platforms. Still, we analyzed our data set further, and the reality is that there's a rather weak correlation between screen size/resolution and the score these devices achieved, which explains why some of the most power-efficient devices are true phablets with Quad HD (1440 x 2560) pixel resolutions. 

In any case, the results speak for themselves: Sony's mini-flagship, the Xperia Z3 Compact, is the most power-efficient high-end device on the planet right now, followed by the excellent Samsung Galaxy S6 Active and the brand-new Galaxy S6 edge+. At the other end of the spectrum, we've got the ZTE Nubia Z9, which thoroughly disappoints in terms of resilience, along with the Nokia Lumia Icon and LG G4. Lastly, it should be noted that, with Apple's iPhones, resolution seems to play a significant part in their efficiency, with the 750p iPhone 6 posting a decidedly better result than the 1080p iPhone 6 Plus.

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