I put the iPhone 17 Pro Max, Galaxy S26 Ultra, Pixel 10 Pro XL, and OnePlus 15 outside in freezing temperatures for a battery drain test — and I’m shocked

iPhone 17 Pro Max vs Pixel 10 Pro XL vs Galaxy S25 Ultra vs OnePlus 15.

(Image credit: Tom's Guide / John Velasco)

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What You Need To Know
Indoor Results
Outdoor Results
Bottom Line

Most of the country is still reeling from last week’s deep freeze, which blanketed areas with record snowfall and dangerously low temperatures. I know very well how battery performance can be affected dramatically by excessive heat, but I wanted to find out exactly what cold temperatures could do.

That’s why I took some of the best phones and ran my own battery drain test to uncover what kind of changes, if any, happen when phones are exposed to frigid temperatures. For this test, I took the iPhone 17 Pro Max, Galaxy S25 Ultra, Pixel 10 Pro XL, and OnePlus 15 because they offer some of the best phone battery life around.

Obviously, there are reliable ways to keep your phone safe from the cold — but I want to uncover the truth behind battery drain in cold weather. The results surprised me. Here’s why.

Flagship phone cold weather test: What you need to know

OnePlus 15 review playing a video outside. — (Image credit: Tom's Guide / John Velasco)

I ended up running two different sets of tests: one indoors and another outside during the late evening when the temperature dropped to 15º Fahrenheit. I also want to point out how long I’ve had each phone, since battery performance typically declines with time. I’ve had the Galaxy S25 Ultra the longest, followed by the Pixel 10 Pro XL, and OnePlus 15. With the iPhone 17 Pro Max, it’s a brand new unit less than a week old.

On both occasions, I charged them to 100% and manually set their display brightness to the maximum level — all while streaming a YouTube clip over Wi-Fi at the “higher picture quality” setting. After each 30-minute increment, I recorded their battery levels and ended the test after two hours.

For the second test, I placed all four phones outside at 9:30 p.m. and kept them inactive for 30 minutes to acclimatize them to the 15-degree temperature. After that, I ran the same battery test as before, streaming the exact same video clip over Wi-Fi.

Unlike the Tom’s Guide battery drain test, which measures performance by setting the display to 150 nits and running a script to simulate average web surfing, my test is a bit more informal. This is exactly why I performed both indoor and outdoor tests: to highlight the specific performance difference for each device.

Indoor room temperature results

Swipe to scroll horizontally

Time (minutes)	iPhone 17 Pro Max	OnePlus 15	Galaxy S25 Ultra	Pixel 10 Pro XL
30	100%	98%	99%	96%
60	100%	96%	96%	89%
90	98%	94%	94%	78%
120	96%	92%	92%	68%

As expected, all four phones felt warm to the touch when I recorded their battery levels after the first 30 minutes. The Pixel 10 Pro XL saw the biggest initial drop, falling to 96% — whereas the other three remained above 98%.

You can see from the chart above how they fared during the two-hour run. The iPhone 17 Pro Max’s performance was particularly notable, ending the test at 96%. I suspect its "fresh out of the box" status heavily impacted the results — especially considering the OnePlus 15 holds the record for the longest-lasting battery life Tom’s Guide has ever tested.

Both the OnePlus 15 and Galaxy S25 Ultra yielded nearly identical results, both finishing at 92%. However, the Pixel 10 Pro XL saw the most significant decline, which only accelerated as the test progressed.

Of all the phones, the Pixel felt the hottest, which likely explains the rapid drain. I suspect the display is the primary culprit here, given that it has the highest peak brightness of the group.

Outdoor freezing temperature results

Swipe to scroll horizontally

Time (minutes)	iPhone 17 Pro Max	OnePlus 15	Galaxy S25 Ultra	Pixel 10 Pro XL
30	100%	100%	97%	96%
60	100%	98%	95%	92%
90	100%	96%	92%	88%
120	98%	94%	90%	84%
150	95%	91%	86%	78%

The outdoor results really shocked me because I was expecting a significant battery drain across the board. In fact, I extended the test by an extra 30 minutes, hoping to see a more dramatic drop-off after the two-hour mark. Despite the frigid conditions, the iPhone 17 Pro Max showed supreme endurance, dropping to just 95% after 2.5 hours of running the test.

Meanwhile, the OnePlus 15 held steady, delivering results nearly identical to its indoor performance and taking second place with a final tally of 91%. The Galaxy S25 Ultra, however, was the only device that performed notably worse in the cold. It recorded 90% after two hours and fell to an even lower 86% by the end of the test.

Most shockingly, the Pixel 10 Pro XL fared better in the deep freeze than it did indoors. After two hours, the battery sat at a better-than-expected 84% — a massive improvement over the dismal 68% I recorded at room temperature. While it eventually reached 78% after 2.5 hours, which is still a significant drop-off, the cold weather clearly helped it maintain its composure longer.

Flagship phone cold weather test: Bottom line

I truly didn’t expect this outcome. On the contrary, I assumed the extreme cold would cause severe battery drain across the board, but the results proved otherwise. Aside from the Galaxy S25 Ultra, every phone in this lineup actually posted better battery life results outdoors in the cold.

My testing reveals that extreme heat is a much bigger battery killer than extreme cold. Whether it comes down to the processor’s efficiency or the effectiveness of the thermal cooling system, it’s evident that heat causes more significant drain — and the Pixel 10 Pro XL is the perfect proof.

At the same time, it seems that battery health and age also play a role. Since it’s less than a week old, my iPhone 17 Pro Max unit appears to benefit from a "fresh" battery, delivering exceptional results both indoors and out. The data might look very different if the device had been in use for several months.

The most surprising takeaway from this "Deep Freeze" test is that frigid temperatures act as a natural cooling system. While all of these phones utilize internal vapor chambers to mitigate heat build-up, this test proves that certain designs are far more effective than others when the environment lends a helping hand.

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John’s a senior editor covering phones for Tom’s Guide. He’s no stranger in this area having covered mobile phones and gadgets since 2008 when he started his career. On top of his editor duties, he’s a seasoned videographer being in front and behind the camera producing YouTube videos. Previously, he held editor roles with PhoneArena, Android Authority, Digital Trends, and SPY. Outside of tech, he enjoys producing mini documentaries and fun social clips for small businesses, enjoying the beach life at the Jersey Shore, and recently becoming a first time homeowner.

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