The Zenfone 9 launched with what was the top of the line SoC from Qualcomm at the time, and the Snapdragon 8+ Gen 1 is still absolutely no slouch in any way, shape, or form even today, despite the fact that its successor is starting to slowly appear on some handsets. We definitely don't think you need to get something with the 8 Gen 2 - there are improvements, sure, but in day-to-day use, it's highly unlikely you'll notice any of them too much.
The Snapdragon 8+ Gen 1 also doesn't have any of the overheating and throttling issues that the non-Plus Snapdragon 8 Gen 1 struggled with, which means it's just a greatly performing high-grade chipset all-round. It is, unsurprisingly, the fastest SoC we've experienced in an Android phone we've had for a long-term review, and - get ready for the cliche avalanche - it absolutely flies no matter what you throw at it.
You can feel the speed regardless of how you use the phone, and you'll never think it's too slow. While this reviewer isn't a mobile gamer and thus can't directly speak to how well those work, note that high refresh rate gaming is possible on this phone, and we assume it's a good experience. In day to day life, the Zenfone 9 will never leave you wanting in the performance department, that much is very clear.
Smoothness is great too, though not quite record-breaking. The OnePlus 10 Pro still holds the crown for the smoothest device we've ever reviewed long-term, but the Zenfone 9 is close behind, almost on par with the Poco F4 GT and the Xiaomi 12 Pro which together hold the second place. The Zenfone 9 is a very close third, with what we're willing to wager would, for most people, be an imperceptible difference between these three.
Of course, smoothness is nothing but a subjective thing anyway, which is why we'd say that, while for us, the Zenfone 9 isn't the top dog, you're unlikely to feel like you need more smoothness from it in real life unless you personally handle one of the aforementioned three handsets that fare higher and do the same things on them side-by-side.
Throughout our use of the Zenfone 9 for this long-term review, battery life has been excellent. It's not the best we've ever seen, but close, and it's better than what most smartphones can boast. That's undoubtedly in part due to the smaller screen the phone employs, but the Snapdragon 8+ Gen 1 chipset definitely had its hand in it too. Anyway, we are most definitely pleased.
With our use case, which is detailed below, going towards 0% we'd always be comfortable expecting at least 7 hours of screen on time. In fact, if you run the numbers in the screenshots below towards zero, you'll see that more than 7 hours might be achievable too, almost on a daily basis. Our record was over 9 hours of screen on time in a day, but that was an outlier. For usage similar to ours, we'd say 7-8 hours is an accurate estimate.
That said, do keep in mind that we use our smartphones primarily on Wi-Fi. Of the total time off the charger, which is normally anywhere between 12 and 16 hours, only about one or two are spent on 5G. Bluetooth is always on, with around 2 hours of listening to music or podcasts each day via TWS earbuds, and there are also calls totaling about an hour. Location is on (including Wi-Fi and Bluetooth scanning), and we use Waze to navigate via GPS for around 30 minutes.
If your use case differs significantly from ours, you can expect proportional variation in the endurance you'll get from the Zenfone 9. If you're constantly on mobile data, perhaps in areas where there isn't a lot of signal, then you should expect significantly lower screen on time numbers. On the other hand, if you spend even more time around Wi-Fi than we do, you may get a bit more. Your mileage will vary for sure.
Charging is handled by a black brick with a matching black USB-C to USB-C cable, and it's not everyday we see such a combo, given how most Chinese companies ship USB-C to USB-A cables that are tailor made for each of their proprietary fast charging systems, and how Samsung and Apple don't give you any brick whatsoever anymore. We also admit having white cable fatigue, so this was a refreshing sight to behold.
The actual charge time itself, however, was disappointing. Sure, going from zero to 100% in 1 hour and 15 minutes seems impressive if your phone is a Samsung, and downright magical if it's an iPhone, but this is way too slow compared to what Asus' Chinese competitors can deliver today, especially since it has a smaller battery to charge than all of them. We're now getting used to seeing under 30-minute charge times on some devices, and under 45-minute full charges on most, and unfortunately the Zenfone just doesn't keep up.
It also doesn't have wireless charging of any kind, which seems like a missed opportunity to counter the slowness of the wired speed with some added convenience. Maybe it's the plastic back that killed it? We'll never know.
There are some interesting battery-related features in Asus' ZenUI, that we felt we should mention. Steady charging slowly charges the battery in order to reduce heat and energy loss, and this can be set to operate within a specific interval (say, at night). It can work in conjunction with Scheduled charging, which dynamically charges the battery to reduce the time that it's full but not in use. Asus suggests scheduling at least a 4-hour period for this in order to ensure optimal battery longevity.
You can also have it so Do not disturb and/or airplane mode are turned on automatically when the phone is charging during its scheduled interval, and set an absolute charging limit to a specific battery percentage, although this makes no sense. Sure, if you do this, and, say, set it to 80%, after 800 charge cycles your Zenfone's battery won't be down to 80% of its initial capacity like most phones' cells - but who cares, since you never took advantage of that extra 20% anyway, by having the setting at 80% to begin with?