The AXE I/O Solo product spec page and the user manual don't list it. I found this quote, which matches up closely with the Wikipedia documentation:
USB 2.0 has the same power limit. But later there were add-ons to the spec for battery charging, allowing up to 1.5A (7.5W) while data transfer is going on, and up to 5A if not.
Below is from Apple StackExchange, showing how to see how much power a device is drawing on a Mac:
How to monitor USB power consumption?USB power consumption information should be available in System Profiler. See the screenshot below:
Hopefully this gets you close to what you're looking for. In general, for USB devices like the AXE I/O Solo, that move and process a lot of data, a USB hub is not a good idea.
Dave