The iOS 11.2 update for iOS users is not ready for the public yet but Apple did release the beta version so at least we know what is coming our way when the update arrives. They also tried charging at the old 5w speed and found that it took 30 minutes to go from 46% to 60%. It is possible that during the time of release of the latest iPhones, Apple did not find the current high-speed chargers available in the market to be safe enough, so it opted to limit the wattage to a lower rating. It was also reported that the wireless charging will work with any Qi charger so you don't really have to get the Apple wireless charger.
The charging pads Apple sells, the Mophie Wireless Charging Base and the Belkin Boost Up Wireless Charging Pad, will both be capable of the new charging speed.
For those of you that prefer the wired method and own one of the latest iPads, you can use the charger that comes with it to charge your iPhone much faster than the charger that comes with the phone.
According to the Apple website, the fastest way to charge the new iPhones is to buy a 29W USB-C power adaptor (£49) and a USB-C to lightning cable (£25-£35 depending on length). During the company's device showcase in September, Apple introduced the very first set of iPhones to support wireless charging. However, reviewers and users have widely claimed that wireless charging on the new iPhones has been pretty slow.
iOS 11.2 has been released to developers and beta testers. Most likely, the next "upgrade" will come alongside Apple's proprietary Apple AirPower, which will be launched sometime in 2018.