Apple is preparing to release iOS 11.2, an update that will enable 7.5W "fast charging" for the new iPhone 8, iPhone 8 Plus and iPhone X.
Currently, iOS v11.1.1 supports only 5W wireless charging; iOS 11.2 is now in beta and expected to ship over the next month or so.
While all three of the new iPhones are capable of taking a charge of up to 15 watts via the Qi v1.2 specification, the iOS platform doesn't support that raten of power transfer. In fact, it only supported 5W charging when originally launched in September.
Additionally, only some wireless chargers support 7.5W wireless charging. Here's a list of Computerworld's top 10 wireless chargers, most of which support the "fast charging" capability.