Tested: Are Google's Tensor chips really that hot and inefficient?

Google’s Pixel smartphones pride themselves on superb software but haven’t quite garnered the same reputation for their processor hardware. Despite custom silicon in the form of Google’s Tensor chip, performance and power consumption have been hit-and-miss. However, things have anecdotally improved in recent generations, including the new Pixel 9 series.

But is there any data to back up many of our gut feelings? We’ve been testing smartphones for years, so I dug out our results for the Pixel 6 Pro and its original Tensor processor to compare against the latest Pixel 9 Pro XL and its Tensor G4, and every model Pro in between. Let’s get into it.

Google’s Tensor under the microscope

First, stress test runs through 3DMark’s Wild Life benchmarks provide us with a very good look at how the phones handle sustained performance when running under heavy load. We’ve tracked the phones’ internal/battery temperature (so how warm the phone feels to the touch rather than inside the CPU) to see if newer models are running hotter or cooler. Think of this as a worst-case scenario rather than anything close to the temperatures you’ll experience scrolling Instagram or flipping through web pages.

Still, the bad news is that temperatures have risen quite sharply. Over the course of the 20-minute test, both the maximum and average temperatures on the Pixel 9 Pro XL were higher than those on the Pixel 6 Pro—from peaks of 40.1°C to highs of 43.2°C. That said, the latest model suggests this trend is slowing when compared to the Pixel 8 Pro, showing only marginal increases in peak and average temperatures.

The exception here is the Pixel 9 Pro; it runs considerably hotter than the 9 XL model and the Pixel 8 Pro. Clearly, the smaller enclosure space leaves less space for robust cooling to move heat away, meaning a warmer phone in hand and the potential for increased performance throttling.

However, temperatures don’t paint the entire picture. While internal heat has gone up, each Pixel Pro model has vastly improved its stress test stability score. This seems counterintuitive but highlights that more recent phones are happy working in higher temperatures environments before throttling performance. How can this be?

Better cooling is most likely to influence these results. These temperatures reflect the heat throughout the device rather than just in the processor. Superior cooling will move that heat away from the SoC and throughout the device. So while your handset may feel warmer, the chip inside is actually running cooler. The Pixel 9 Pro versus Pro XL is again a great example of this; it’s the same chip, but a smaller area to dissipate heat results in higher temperatures and more aggressive performance throttling on the Pro.

Efficiency can also help in this regard. A processor that’s better at converting power into performance and wasting less as heat is less likely to need to throttle back performance to keep temperatures under control. Thermal runaway is far less likely. The Pixel 6 Pro demonstrates this quite well; it appears to run the coolest and yet has the worst stability score, suggesting a higher build-up of heat inside the chip. Meanwhile, the Pixel 7 Pro produces similar temperatures and yet offers improved stability. Google acknowledged that the Tensor G2’s 5nm node was more efficient than the original Tensor’s.

What about efficiency and battery life?

Power consumption is the other half of the equation, and for that, we can turn to our in-house battery test to see if there have been any gains here to support the theory about improved efficiency. We look at a variety of metrics to get a solid overview of various typical scenarios, from web browsing to video recording. The Pixel Pro series’ cameras and displays have changed a bit, so there’s some leeway in the results. Still, battery capacities have barely changed over four generations, at 5,003mAh, 5,000mAh, 5,050mAh, and 5,060mAh, respectively.

There’s a clear trend in longer battery life with the move to newer models. Whether you’re browsing the web, recording video, or making video calls, we can see a notable jump between the original Tensor and Tensor G2 in the 6 Pro and 7 Pro. We’ve seen a further leap with the move to the Pixel 9 Pro XL, owing to the move to a more efficient manufacturing process, as the rest of the chip is virtually unchanged. Our gaming benchmark is the only exception, but that’s likely because performance gains come at the expense of the efficiency wins — hence the higher temperatures too.

Averaged across our tests, the Pixel 7 Pro is 35% more battery efficient than the 6 Pro, the 7 Pro and 8 Pro are roughly the same, and the 9 Pro XL sees an 11% jump over the 8 Pro. There’s a whopping 48% battery longevity boost from the first-gen Tensor chip inside the Pixel 9 Pro to the Tensor G4 inside the Pixel 9 Pro XL. That’s quite an improvement over just four years.

Of course, we expect processors to become more efficient every generation or two, owing to the move to more efficient manufacturing nodes. Google’s Tensor has gone from Samsung’s dubious 5nm LPE to a much improved Samsung 4nm (possibly 4LPP+) process with the Tensor G4, and the results outlined here show clear benefits of the newer chip and its manufacturing process.

The picture’s clear, but there’s even more to the story that falls outside of testing. Google’s choice of modem, for instance, impacts networking efficiency and temperatures, which are particularly noticeable when roaming in poor signal areas. Tensor has adopted newer Samsung Exynos modems, including in the latest Pixel 9 series, which boast far greater efficiency, bringing the phones much closer to Samsung’s flagship Galaxy S series. Anecdotally, we’ve noticed much-improved connectivity and less battery drain as the generations have gone by.

That said, we’ve still felt these phones heat up from time to time (but what phone doesn’t), suggesting future Pixels could still benefit from more cutting-edge manufacturing processes like TSMC’s 3nm, which you’ll find in flagship handsets arriving by early 2025. Next year’s Tensor G5 is expected to move over to TSMC, suggesting that the series’ best years are still yet to come with the Pixel 10.