iPhone Duo reviews find varying effects from heat
One gaming test recorded 46.5°C and reduced brightness, while other reviewers reported warmth without a noticeable performance impact.
Reviewers testing the iPhone Duo reported differing experiences with heat, with some finding slowdowns during demanding tasks and others seeing no performance problems. Camera use, video apps and gaming were among the activities associated with higher temperatures.
HTX Studio measured the Duo at 46.5°C during a 30-minute gaming test, against 43.8°C for the iPhone 18 Pro and 43.2°C for the Pro Max. It reported a frame rate 20 percent below the iPhone 18 Pro models. Screen brightness fell to 185 nits after the Duo could not sustain 300 nits.
The Verge reported increasing heat during extended camera use, particularly with both screens active, followed by noticeable lag. Joanna Stern ended a FaceTime test call because the phone became too hot. Apple told Stern that warmth reflected its thermal system carrying heat away from the chip to sustain performance.
Other assessments were less critical. According to 9to5Mac, the Duo ran warmer than the iPhone 18 Pro without affecting performance. Gizmodo reported no heat-related problems. Tom’s Guide found that heat spread evenly through the body and measured a 75.9 percent stability score in the 3DMark stress test.
In a separate 20-minute stress test, Mrwhosetheboss found that the closed Duo retained heat and performed below the iPhone 18 Pro Max. He nevertheless described the everyday performance gap as limited.
The Duo shares the iPhone 18 Pro’s A20 Pro chip but uses a thinner version of its custom vapor chamber. A flexible graphite pipe within the hinge carries heat between the device’s halves, expanding the area available to dissipate it.
