In a recent test, Tom's Guide used a Flir One Pro thermal camera to measure heat generation in the Galaxy Z Fold 8 Ultra, Galaxy S26 Ultra, Galaxy Z Fold 7, and iPhone 17 Pro Max. The phones were run through 3DMark's Solar Bay Extreme Stress Test for 10 minutes.
The Galaxy S26 Ultra heated up fastest, reaching around 30°C in a minute and approaching 40°C by the 4-minute mark. The iPhone 17 Pro Max followed closely. The foldables, when closed, heated up more slowly, hovering between 35°C and 37°C by the end of the test.
When unfolded, the Z Fold 8 Ultra and Z Fold 7 showed rapid heat buildup, exceeding 40°C within a minute. Heat concentrated near the camera bar and spread across the left side, struggling to cross the hinge. The S26 Ultra concentrated heat in the top left, away from the camera bar, due to its vapor chamber.
The test suggests that while peak temperatures are similar, the S26 Ultra's vapor chamber actively routes heat away from components, whereas the Z Fold 8 Ultra lacks such cooling, allowing heat to spread more broadly. This could affect long-term performance and lifespan under sustained heavy use.
Tom's Guide notes that short bursts of high-performance activity may not pose long-term issues, as temperatures dropped quickly after the stress test ended. They advise keeping phones cool during heavy use, avoiding direct sunlight, and not using refrigerators to cool devices.
Source: tomsguide.com
