If I'm Samsung and I'm getting my new Galaxy S26 models ready to launch in a month or two, the arrival of the OnePlus 15 would be making me very nervous. Because the latest flagship phone from OnePlus, now available for pre-order in the U.S., serves to underscore an area where Samsung is at risk of falling behind.
The OnePlus 15 offers the best phone battery life of any device we've ever tested. When Tom's Guide reviews a phone, we set it up to surf the web continuously until it runs out of power, timing how long that takes. In the OnePlus 15's case, that's more than 25 hours — nearly 5 hours better than the next longest-lasting handset.
That's not to suggest Samsung flagships don't last a long-time on a charge. When they debuted at the start of the year, all three Galaxy S25 models landed on our list of the longest-lasting phones, though subsequent releases in 2025 have knocked some of those Samsung devices out of the top rankings. Get any Galaxy S25, and you're going to get a phone that lasts all day on a charge.
It's rumors about the upcoming Galaxy S26 releases that have me concerned. At a time when other phone makers seem to be taking improved battery life very seriously, rumored enhancements to the next Galaxy S models have me wondering if you can say the same thing about Samsung.
Galaxy S25 battery life
We first tested the Galaxy S25 series shortly after the three phones launched at the end of January 2025. As you might expect of the model with the biggest battery, the Galaxy S25 Ultra set the pace, posting an average of 17 hours and 14 minutes. But the Galaxy S25 Plus (16:55) and Galaxy S25 (15:22) put up great times, too. (We're ignoring the Galaxy S25 Edge, which came out later and has a much smaller battery due to its thinner design.)
The Galaxy S25's battery test result looked especially impressive at the time, as that was the most compact phone in that initial release of S25 models. Even with a 4,000 mAh battery — the Plus and Ultra models have much larger power packs — the standard S25 managed to deliver more than 15 hours of continuous surfing on one charge. That's very impressive.
Phone | Battery size | Battery life (Hrs:Mins) |
OnePlus 15 | 7,300 mAh | 25:13 |
iPhone 17 Pro Max | 4,823 mAh | 17:54 |
Galaxy S25 Ultra (February 2025 test) | 5,000 mAh | 17:14 |
Galaxy S25 Ultra (September 2025 test) | 5,000 mAh | 14:27 |
In the ensuing months, we've updated our battery test, and while we didn't retest every Galaxy model, we did run the new version on the S25 Ultra in order to compare that phone to Apple's iPhone 17 releases. Under the new test, the S25 Ultra fell shy of the 15-hour mark.
My takeaway is that Samsung's current flagships still last a long time on a charge, but they don't quite measure up to devices from Apple and OnePlus that have come out since Samsung's last flagship release.
Galaxy S26 battery rumors
The Galaxy S26 launch — which could happen as soon as January, though some rumors expect a later release in early 2026 — gives Samsung the opportunity to show that it's just as serious about boosting battery life as its rivals. But current Galaxy S26 rumors don't paint a particularly encouraging picture.
A specs post from a fairly reliable leaker at the start of December has the standard Galaxy S26 model seeing a modest boost in battery size, from 4,000 mAh in the S25 to a 4,300 mAh power pack. However, that same post has the Galaxy S26 Plus and Galaxy S26 Ultra with the same 4,900 mAh and 5,000 mAh capacities as their respective predecessors.
There's not universal agreement about the potential battery size for the Galaxy S26 Ultra. Some rumors suggest Samsung will go with a 5,200 mAh cell — an increase, though not much of one, from the Galaxy S25 Ultra.
| Row 0 - Cell 0 | Rumored battery size (mAh) | Battery size of equivalent S25 model (mAh) |
Galaxy S26 | 4,300 | 4,000 |
Galaxy S26 Plus | 4,900 | 4,900 |
Galaxy S26 Ultra | 5,000 - 5,200 | 5,000 |
We should point out that there's more to battery life than just the size of the power pack. The Galaxy S26 series is in line to feature Qualcomm's new Snapdragon 8 Elite Gen 5 silicon, and that system-on-chip promises more efficient power management as part of its feature set.
Even if some S26 models use the Exynos 2600 chipset instead as has been rumored, the latest Exynos silicon is built on a 2-nanometer process, so the transistors will be more densely packed than the 3nm Exynos 2500. That usually translates to better power efficiency.
Nevertheless, the leaked Galaxy S26 specs would seem to suggest that rumors from earlier this year that Samsung would turn to a silicon-carbon battery for its upcoming flagships aren't going to happen. Silicon-carbon batteries are denser than the current batteries in use by smartphones, so they can pack more capacity without increasing in size.
It's this technology that allows the OnePlus 15 to feature a 7,300 mAh battery while still maintaining a reasonable 6.4 x 3 x 0.32-inch frame in a 7.4-ounce handset. And it sounds like something the Galaxy phones — especially the Galaxy S6 Ultra — are going to miss out on.
Galaxy S26 battery outlook
I would definitely expect some boost in battery life for Samsung's next phones — a new chipset and even a modest increase in battery size will see to that. But you can't help but look at what OnePlus achieved in boosting the battery life of its flagship phone and feel like Samsung is potentially missing out.
But rumored specs are exactly that, and we won't know how long Samsung's next phones can last until we get a chance to test them next year. It's one of the many improvements we'll be keeping an eye on as we get closer to the rumored Galaxy S26 launch./
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