Aye and that’s only the peak, usually it hovers between 12-15W. The XTPower has an integrated display, showing the current draw. Additional info for anyone interested:
Your solution also works, since the power draw is pretty low, but in general I recommend avoiding 5V->12V converter cables and rather go for powerbanks which have an 12V option directly integrated, allowing you to push way more Ampere or at least have the reserves for that.