We’ve known for years that connecting over Wi-Fi uses less power than relying on mobile data on the iPhone. It makes sense: the cellular antenna needs more power to maintain the connection. But there’s always the question: how big is the difference, really? A recent test with the iPhone 17 Pro Max puts clear numbers on it and, honestly, they’re quite interesting.
Wi-Fi vs 5G: around three extra hours of use
PhoneBuff did something very simple (and very useful): it repeated the same everyday usage in two identical scenarios. It took an iPhone 17 Pro Max and simulated real tasks like messaging, web browsing, streaming video, using Instagram, and making FaceTime calls, measuring how long the battery lasts on 5G and how long it lasts on Wi-Fi, keeping the rest of the conditions as similar as possible.
The result is fairly straightforward to interpret. The iPhone using 5G reached about 10 hours and 22 minutes of active screen time before running out. When that device drained its battery and shut down, the Wi-Fi-connected model still had around 25% battery remaining, which works out to roughly three additional hours.
Although it’s important to remember that on earlier models this difference is larger. Older modems need more energy and, in practice, Wi-Fi extends battery life even more.
Here we can see the full test:
Coverage and movement matter more than it seems
The test has a small but important detail: the phones stay still and with a strong signal. On the move, things change. When we walk or travel, the iPhone is constantly switching antennas, recalculating transmit power, and keeping the network stable. That makes power consumption rise substantially.
In areas with uneven signal, the modem has to work harder and the drain increases. So on train, metro, or car journeys, for example, the difference between Wi-Fi and 5G is usually quite a bit greater than that 25%. That’s because the cellular network has to continuously negotiate with nearby towers, while Wi-Fi is typically just a few metres away and stable. That’s why, when we get home, we see the percentage drop more slowly without touching any settings.
Conclusion? When we have Wi-Fi available, using it extends battery life and can even give us better speed and quality. And when we depend on 5G, consumption remains reasonable thanks to the efficiency of today’s iPhones (or thanks to good external batteries like Ugreen's MagSafe Battery). Internally, our iPhones do a lot to offer us the best speed and battery life; on our side, the simple act of connecting to a Wi-Fi network radically changes what the phone can offer us.
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