The iPhone 6 and 6 Plus this year come with larger batteries compared to last year's 5S. Larger batteries also usually mean longer charging times. However there is a neat trick to charge your phone quicker.
MacRumors tested the standard iPhone charger and iPad charger and found that the iPhone 6 is now able to draw 12W instead of the regular 5W. This means it can charge at a quicker rate and draw more power.
I've been using the iPad charger myself and have found that it charges at a noticeably quicker rate when compared to the standard charger that comes with the phone.
The iPad charger costs only £15 but you could use other 12W chargers that are cheaper. However you run the risk of using an unauthorised charger then that could destroy your battery or even your device.