iPhone 18 Pro benchmark boosted by giving it a cold drink

3x the vapor-chamber surface area can only do so much; luckily the fridge helped with sustained performance

There’s nothing a quick break for a can of ice-cold sparkling water can’t solve - including improving thermal management on the iPhone 18 Pro, as it turns out. 

Software developer Matt Birchler provided the data to prove it in a recent blog post detailing a bit of extra experimentation he did with his new iPhone 18 Pro alongside some benchmarking work. 

To make a long story short, a cold can of La Croix (in Birchler’s case – the cooling potential of an aluminum can isn’t limited to name-brand sparkling “naturally essenced” water) takes an already beefy device to new levels of sustained performance by helping it shed heat and avoid thermal throttling.

REG AD

One of the most notable upgrades in the latest version of Apple’s flagship smartphone is that vapor chamber, with the 18 Pro series containing one with three times the surface area of the version introduced in the 17 Pro series.

REG AD

For those not familiar with the intricacies of modern smartphone guts, vapor chambers are a standard part of today’s top-tier devices. They’re small, sealed units placed next to processors that contain a minuscule amount of water and a metal wicking structure, ostensibly to keep high-end chips from overheating. As the water evaporates, the vapor moves away from the chip side of the chamber toward cooler areas, where it condenses. The wicking structure then carries the liquid back toward the hot spot, allowing the cycle to begin anew.

As Birchler notes in his post about the iPhone 18 Pro’s benchmark performance, that improved vapor chamber size is in part responsible for its increased performance - sure, a beefier chip helped too, but this is a story about thermal management. 

Birchler ran an iPhone 18 Pro, 17 Pro, and M4 Pro MacBook Pro through a benchmarking tool included in an audio transcription app he built called Quick Subtitles. The test ran 20 times on each device using a built-in benchmarking file and used Apple’s on-device transcription model to do its work.

The 18 Pro clocked some impressive performance, varying between 447.9 and 320.9 words per second over the 20-run test - a 50 percent performance jump over the 17 Pro. Both devices heated up, but at a different rate. 

“It took a bit longer for [the iPhone 18 Pro] to start warming up, but once it did, it actually warmed up quicker than the iPhone 17 Pro,” Birchler wrote. “To be clear, this wasn't just in the metrics. I could also feel the temperature difference in the hand. The 18 Pro was definitely a bit hotter.”

To be fair to Apple’s designers, that’s not a flaw in the 18 Pro’s design: A larger vapor chamber should be pulling more heat from the phone’s processor and distributing it over a larger area of the device, meaning it should be getting a bit warmer than the previous model with its less efficient vapor-cooling design. 

To get to the heart of the matter, Birchler still wanted to see if he could get improved performance by reducing the thermal throttling the iPhone 18 Pro was experiencing. Based on the results in his full benchmarking run, the 17 Pro may never have performed as well, but it was being throttled less than the 18 Pro over the course of 20 runs - that bigger vapor chamber still wasn’t getting rid of enough heat, it seems, even though Apple’s made it better.

“It’s clearly doing what it’s supposed to do, and in the other test you can see that when it’s throttling down due to heat, it’s losing less performance than last year’s phone,” Birchler told The Register in an email. “Chips that are passively cooled will always have some level of throttling, so it’s good to see progress here.” 

REG AD

Either way, if Birchler wanted to push the iPhone 18 Pro to its limits, he was going to need some outside help, and he knew right where to turn: The fridge.

“I know from experience that if you put a cold beverage on the back of your phone, it will cool down really quick, so I thought…the test is obvious,” he wrote. “I took a cold La Croix out of the fridge, started a new benchmark run, and put the can on the phone. When I came back, the job was done and the results were exactly what I'd hoped they'd be.” 

The iPhone 18 Pro’s benchmarking performance was practically unchanged when a cold can of fizzy water was placed on its backside: Its first run clocked in at 429.9 words per second, and by the end of the 20th run it was still transcribing an impressive 400.4 words per second. 

iOS only tells developers whether the thermal state of a device is nominal, fair, serious, or critical, Birchler told us. Without the assistance of the La Croix can, the 18 Pro spent around half the runs in the serious zone, and, with the can, it never rose beyond a fair thermal state. 

In other words, next time you want to do some heavy work on your iDevice, just start the task and pop a cold can of whatever on the back of it. You might look crazy, but you’re going to get the work done 14 percent faster if Birchler’s experiment holds true across other types of work.

“When they call you crazy, you turn around and tell them they don't know what they're missing,” Birchler advises.  ®