Best overall
Huawei Mate 9
With a massive 5.9-inch display, you'd think that the Huawei Mate 9 wouldn't be able to last a whole day — but you'd be dead wrong. That screen is helped along by a 4,000mAh battery — one of the biggest in its class — pushing the Mate 9 to a staggering 2-day average uptime. Huawei's flagship device also has some Machine Learning chops that learn what apps you use most and least, in order to optimize them for battery usage.
Bottom line: A huge 4,000mAh cell plus software optimizations make the Huawei Mate 9 the best phone for battery life.
One more thing: Sometimes the Mate 9 can push battery optimizations a bit too far, so be sure to tweak your app settings when appropriate.
Why the Mate 9 is the best
An underrated performer in the U.S. because it doesn't have carrier support, but the Huawei Mate 9 is a serious worker.
Huawei has come a long way since its days of questionable software and China-only releases. The Mate 9 is now officially available in the U.S., and you get a lot with its $599 price tag, including a 4,000mAh battery that has to be one of the best out there. The company's homegrown Kirin 960 chip is not only fast, but its 16nm manufacturing process makes it extremely efficient.
Combined with the power-sipping 1080p LCD panel, the Mate 9 seemingly lasts forever; there wasn't a single day that reviewer Alex Dobie worried about it dying by the afternoon:
The phone never failed to get us through a full day of mixed use on LTE and Wi-Fi, often with more than 50% in the tank by the evening. Even pushing the phone really hard with lots of photography and a little wireless tethering, we never came close to experiencing battery anxiety.
Other than battery life, the Mate 9 is just an all-around great phone, and Huawei has committed to updating it with Alexa support in the coming months.
Best for sleekness
Samsung Galaxy S8+
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The Galaxy S8+ is the spiritual battery successor to the Galaxy S7 edge, and despite having a slightly smaller battery does an amazing job keeping the phone alive for as long as possible. That's partly due to the amazing efficiency of the Snapdragon 835 chip, which we're starting to see in more devices this year, but the GS8+ manages to outlast them all.
Bottom line: The Galaxy S8+ is a sleek, sophisticated and powerful Android phone — probably the best available overall — with amazing battery life.
One More thing: This highly-rated device is available at all four major carriers in the U.S., but if you'd rather live dangerously and contract-free, Samsung offers an unlocked model that also works overseas.
Best for less
Moto Z Play
The Moto Z Play starts quickly and keeps going. It's actually quite amazing to witness. Thanks in part to the super-efficient Snapdragon 625 processor, which is built on a 14nm process, the phone rarely gets hot, and with eight cores, works smarter, not harder.
With a 3,510mAh battery inside, along with software that feels as light as a feather, the Moto Z Play is the longest-lasting $400 phone we've used. It's also a pretty great smartphone, featuring a bright 5.5-inch display, a great 16MP camera, and support for Moto Mods.
Bottom-line: The Moto Z Play doesn't sacrifice much from its more expensive, much thinner Moto Z sibling. If you can deal with the added girth, and a slight hit to processing abilities, you get one of the best, longest-lasting Android phones around.
One more thing: Pair the Moto Z Play with Incipio's 2,220mAh OffGrid battery pack, and you have a whopping 5,730mAh combination that should last two full days, or longer!
Best for hard workers
BlackBerry KEYone
The BlackBerry KEYone is, unsurprisingly, a workhorse. There's a lot going on beneath those classic BlackBerry keys, but the one thing you need to know is, like the Moto Z Play, it pairs a massive battery with an energy-sipping Snapdragon 625 processor. If you're longing for the good 'ol days of not having to charge your BlackBerry everyday, the KEYone fits the bill nicely.
Bottom-line: The KEYone is an exceptional phone with a near-perfect hardware keyboard and multi-day battery life.
One more thing: There are two separate variants of the KEYone, one for AT&T and T-Mobile and another for Verizon. Choose wisely.
Conclusion
Most phones claim to have "all-day battery life," but few actually make it to bedtime. The Huawei Mate 9 actually backs up its claims, and does so while excelling in almost every other area.
Best overall
Huawei Mate 9
With a massive 5.9-inch display, you'd think that the Huawei Mate 9 wouldn't be able to last a whole day — but you'd be dead wrong. That screen is helped along by a 4,000mAh battery, one of the biggest in its class, pushing the Mate 9 to a staggering 2-day average uptime. Huawei's flagship device also has some Machine Learning chops that learn what apps you use most and least, in order to optimize them for battery usage.
Bottom line: A huge 4,000mAh cell plus software optimizations make the Huawei Mate 9 the best phone for battery life.
One more thing: Sometimes the Mate 9 can push battery optimizations a bit too far, so be sure to tweak your app settings when appropriate.
Update June 2017: The Mate 9 stays on top of the list with its huge battery, but the Galaxy S8+ takes over from the GS7 edge and the Honor 8 gets bumped for the BlackBerry KEYone.