To get a sense of how much extra power is lost when using wireless charging versus wired charging in the real world, I tested a Pixel 4 using multiple wireless chargers, as well as the standard charging cable that comes with the phone. I used a high-precision power meter that sits between the charging block and the power outlet to measure power consumption.
In my tests, I found that wireless charging used, on average, around 47% more power than a cable.
Charging the phone from completely dead to 100% using a cable took an average of 14.26 watt-hours (Wh). Using a wireless charger took, on average, 21.01 Wh. That comes out to slightly more than 47% more energy for the convenience of not plugging in a cable. In other words, the phone had to work harder, generate more heat, and suck up more energy when wirelessly charging to fill the same size battery.
We know that wireless charging is slower than using a cable, but now we have some numbers to understand that it’s not just slow but also not energy efficient.
Wireless charging is convenient, but only to a certain extent. It is just slightly more convenient than taking a few seconds to plug in a cable. But if you need to do something on the phone while it’s charging, chances are you’ll have to remove it from the charger. With wired charging, you can keep the cable plugged in to reply an urgent message.