...you definitely want one of those plug-in USB power meters. That'll tell you a lot about what's going on.
@andymanone: That's what I also recommend for tweaking and bug-fixing. The bitshopper.de manufactured ones are tested with this one:

Yes, I know this power meter very well and use it too very often of course

!

But it´s limited by
about 3Amp max, and my Gekko
runs up to 25Watts peak , so its not usable for me in this way...
Thatswhy I´ve choosed other options, for instance my networkbased Poweranalyser (with a software client)

Cheers,
andY