Get the Tacx Utility app on your phone. It is simple once you connect your phone to the trainer.

It's not just my Tacx Flux that reads low. So do my Assioma's. :-)

Ok. Thanks!

Not sure if anyone else picked up on this but I did!! I think many of us have this problem....

I have been using a first gen flux for a couple of years now in a garage. The power readings are pretty sensitive to temperature swings so I have to calibrate it regularly. I have also noticed more recently that the trainer is doing some serious power smoothing/average. I suspect this was delivered as a firmware update at some point and gives the impression that power is lower especially when accelerating. When comparing power data collected on my head unit from Garmin vectors and from Zwift from the trainer everything is pretty close on average but often the values I see on the screens are >10% different. I have stopped using ERG mode on the trainer as a result because it doesn't accurately hit the prescribed power targets.