Wireless charging has been around for more than a quarter of a century, but only over the past decade did smartphone manufacturers begin offering it natively in their handsets.
In 2012, Nokia was the first to adopt the Qi-based wireless charging in its Lumia 920 phone.
Because they want to keep the device nice and thin, they didn't want to go with the crowd," said William Stofega, IDC's program director for mobile phones.
Why Apple chose a slower version of wireless charging than the latest Android smartphones, which offer 10W of charging power, is unclear.
The cost of wireless charging components rises in tandem with the power level, according to Menno Treffers, chairman of the Wireless Power Consortium, which oversees the Qi wireless charging standard.
"There are tradeoffs and we leave it to our members to make their own tradeoffs and optimize for their intended customers.