Vector 3 measures less power than WAHOO kickr. Can someone help? It's constantly 20W less after countless of calibration of both devices.

Which Kickr? A newer one or an older (1st or 2nd gen) model? Do You have comparison charts? (ZwiftPower dual links or DCAnalizer links?)

The newest Kickr. Do you have some instructions on these comparison sheets?

Do You have ZwiftPower registration? (There is a feature where You can upload 2 FIT files and get a chart) If not, if You send me 2 FIT files with the 2 power sources then i can do a comparison easily. 

The latest Kickr v5 has auto calibration already (probably You need to enabled it in the Wahoo app, but the manual spindown is also ok), so if You have 20w offset difference (and thr V3 is the lower) then (imho) something is wrong with pedal('s setting). How is your balance? 50-50 or much more unbalanced? Is the crank length setting is correct in the head unit/wristwatch also ? Because if You set it only in the G.connect app and not in the head unit then the head unit is overwrite this setting and i have seen bad crank length (140mm accidentally due to some reason) setting in head unit and it ruined the measurements.

zwiftpower.com/analysis.php

zwiftpower.com/analysis.php

?set_id=79355 is one of them, the other is ?set_id=79354

I also checked and the crank lengths are OK. I have Vctor 3s so can't tell the balance. I doubt it's this much off.

i wrote You on private m. 

I have the same problem. My Vector 3 shows around 20W less than my kickr.

I tried to follow the posts but it's not clear to me what the soulution could be (if there is any)