Phone battery life has made some incredible progress in the past few years, and nowhere is that more true than with Asus’s ROG Phone series. A member of this gaming phone line always seems to sit at the top of our best phone battery life list, and despite strides made by the likes of the iPhone 16 Pro Max, it seems nobody can catch up.
But now we have the Asus ROG Phone 9 Pro, the question is if it will impress as much as the Asus ROG Phone 8 Pro did last year — when it scored almost 19 hours in our custom battery life test. The short answer is that yes it has.
Our battery life test involves continuously reloading web pages over a 4G cellular connection, with the screen set at 150 nits of brightness. This process continues until the phone’s battery dies, and earning a spot on our best phone battery life list means being in the top 15 longest results recorded on the test.
Currently, phones need to last about 14 hours to be in with a chance of getting on the list. And we’re happy to say that the Asus ROG Phone 9 Pro smashed that target with room to spare — lasting 20 hours and 34 minutes before the battery died.
That’s incredibly impressive battery life, and beats the Asus ROG Phone 8 Pro, our previous no. 1 entry, by over 100 minutes. That was with the screen set to automatic refresh rate, though, so if you lock the ROG Phone 9 Pro to its maximum 185Hz refresh rate at all times, you won't get nearly as good a result. Still, it shows that no matter what other phone companies seem to do with their batteries, Asus always seems to be one step ahead.
| Phone | Battery Size | Battery test results (Hrs: Mins) | Charging Speed | % Charged after 30 mins |
| Asus ROG Phone 9 Pro | 5,800 mAh | 20:34 | 65W | 74% |
| Asus ROG Phone 8 Pro | 5,500 mAh | 18:48 | 65W | 71% |
| iPhone 16 Pro Max | 4,685 mAh | 17:17 | 45W | 56% |
| Samsung Galaxy S24 Ultra | 5,000 mAh | 16:45 | 45W | 71% |
| OnePlus 12 | 5,400 mAh | 17:05 | 80W | 97% |
| OnePlus 12R | 5,500 mAh | 18:08 | 80W | 96% |
The ROG Phone 9 Pro has done a lot better than just beating its predecessor. It’s also knocked some of the biggest and best smartphones of 2024 further down our best battery life list. That includes the iPhone 16 Pro Max, which scored 17 hours and 17 minutes, and performed so well in battery testing that we had to redo the testing multiple times to make sure it wasn’t just a fluke.
20 hours and 34 minutes absolutely dwarfs the OnePlus 12 and Samsung Galaxy S24 Ultra, which scored 17 hours 5 minutes and 16 hours 45 minutes in testing. The ROG Phone 9 Pro even beat out the OnePlus 12R, which has a much larger 5,500 mAh battery than all three of the other phones phones — rivaling the Asus ROG Phone 8 Pro. But its 18 hour and 8 minute battery life doesn’t even come close to the new first place entry.
This kind of battery performance doesn’t come out of nowhere. The Asus ROG Phone 9 Pro has an enormous battery, rated at 5,800 mAh, which you’d hope would last a long time. That battery works out at 300 mAh larger than last year’s model, which would explain some of the additional battery life.
We should also point out that the ROG Phone 9 Pro is one of the first phones running on the new Snapdragon 8 Elite chipset, which is built using a 3nm process. That process means smaller chips, and allows the chip to boost performance while lowering energy consumption — a crucial element to long battery life.
In the unlikely event that the ROG Phone 9 Pro does die on you unexpectedly, it can fall back on the impressive 65W wired charging speeds. According to our tests, that restored 37% of the battery life in just 15 minutes, and 74% after half an hour. Wireless charging isn’t nearly as impressive, though, and the 15W wireless charging speed is going to take a while to make a dent in such a large battery.
It will be interesting to see how the competition fares against the Asus ROG Phone 9 Pro’s impressive battery life in the coming months. Especially if they have a Snapdragon 8 Elite under the hood. But for now, if you’re looking for the best possible battery life, then you might want to check out what Asus has to offer.
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