You must have noticed that your phone or tablet charges slower if you connect it to your Laptop or PC’s USB port than when you put it in charge directly from the power adapter. You also may have noticed that the phone charges fast when you connect it to charger that came with the phone because power output is different for different chargers.
You may have seen that a PC’s USB is mentioned like 4.5W for USB3.0 and 2.5W for USB2.0 and 1.0 and a phone’s charger is rated as 10W or 5W.
The wattage is calculated by multiplying the voltage and current. For example, if in the charger there is mentioned 5V, 1A, then it generates 5W power and if the charger is rated a 5V, 2A, then the generated power is 10W.
One thing you should remember that if your phone is specified at 5W but you connect a charger that can supply 10W, your phone will not draw extra power, it will draw only what is required. So do not think your phone will charge faster if it is connected to a higher-specified charger.
But some phones and tablets accept higher input also.
Now if you want to charge your iPad or iPhone faster from a Mac, then the iDevice has to be the first device connected to the Mac. If you use Apple mouse and wired keyboard, then remove them first, then connect your iPhone or iPad with the PC. Now connect the mouse and keyboard.
Another potential tip is to turn off your iPhone or iPad or put it in Flight mode for one or two hours when it is charging. It will charge your iPhone faster because no other tasks will be performed which will not cause any battery drain.