I don't bother using the reported power off of either of my trainers (Kickr Snap and Kickr). Both consistently read 5-10% higher than my P1 or G3 (which I suppose is within the spec range). It's almost comical. On the Snap in erg mode, I can be doing 100w, then the next interval is at 250w and the reported power instantly jumps to a perfect 250w before the resistance even kicks in. Which makes me think that the Snap just reports target power.