Apple's iPhone 8 features quick charging, which is great, because slow charging has long frustrated iPhone owners. We tried three different chargers and found that Apple's $19 iPad charger offers the best balance of fast charging and low price, using cables you already own.
Charging speed doesn't increase linearly as you pump more juice into a battery. To keep batteries safe, they're limited in terms of the energy they take in at once. To prevent accidental explosions, they take in less energy per minute the more full they get—that's why it's much easier to fill your phone from 0-50 percent than from 90-100 percent. Putting bigger chargers on your iPhone is going to result in faster charging, but there's a curve involved.
Using the 5W charger which comes with the iPhone 8 Plus, we filled 38 percent of the battery in an hour. That's the kind of performance that has frustrated iPhone owners in the past—plugging in a dead phone for half an hour and having to walk away with only 20 percent or so of charge.
Using a $19 12W iPad adapter with the iPhone's included USB-to-Lightning cable made a huge difference. Now, one hour charged us to 72 percent. In terms of currently available chargers, we really consider that to be the sweet spot, but it isn't by a long shot the quickest charging available. For that, you need a USB-C cable and power adapter.
We tried an Anker 30W PowerPort Speed, which uses USB-C power delivery to pump out 30W worth of power and should really accelerate charging. Unfortunately, the iPhone doesn't come with a USB-C cable, and the only one certified for power delivery is Apple's $25 USB-C-to-Lightning cable. So that brings the charge for your charging up to $46.59.
It's also not that much faster. In one hour, we filled 84 percent of our iPhone 8 Plus battery using the USB-C charger. Yes, that's more than the iPad charger accomplished, but not, in my mind, enough to justify the added cost.
The cost, really, is the problem for us. If the iPhone came with a USB-C cable, the faster Anker charger would absolutely beat the iPad charger. But at $25, that's an expensive cable.
Dedicated USB-C-based iPhone fast charger sets and better, cheaper cables will probably come out over the next year. But for now, that iPad brick brings you the best bang for your buck.