Each USB device that you connect to your Windows computer, or even iPad, will consume power in order for it to function properly. Let’s say you connect a keyboard to your iPad via an OTG cable, this keyboard will draw some current from the iPad in order to function.

To find out how much power a USB device is consuming, you can use a little (portable) program called ChipGenius. You only have to download ChipGenius from the website of the developer, and run it.

In the top, you will see each USB controller/device that is present in your system. Select the device you want to see the current from. In my case, I wanted to know how much power a USB mouse receiver uses to interaction with my wireless mouse. The max current is 100mA, so there is my answer!

Description: USB Composite Device(Compx 2.4G Receiver)
Device Type: Human Interface Device
Protocal Version: USB 1.10
Current Speed: Full Speed
Max Current: 100mA
USB Device ID: VID = 25A7 PID = FA23
Device Vendor: Compx
Device Name: 2.4G Receiver
Device Revision: 0232
Controller Part-Number: Unknown

The same method should work for virtually any USB device you connect. This includes:

• USB Flash drives (thumb drive)
• Keyboards
• Mice (wired or wireless)
• Dongles
• Cameras
• …