Do you have the latest firmware for both Stages and Wahoo? It’s also very possible that the Stages is reading high. Is it a single side Stages?

So who knows which device is actually off.

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Favorite Gear: Dimond | Cadex | Desoto Sport | Hoka One One

Have you contacted Wahoo about it? I think that would be an excellent first step.

Yes, just looking to get some additional experiences

Well, the first difficulty is establishing the accurate baseline. I had a similar problem with my Tacx Neo 2, but I had the baseline knowledge that 2 pairs of PowerTap P1 pedals, Assioma Duo pedlas, KICKR 2016, and my Kirt Kinetic InRide virtual power were all pretty consistent with one another. So, when I saw the Tacx error, I had high confidence that it was the Tacx' fault.

• What is the percent difference-- is it 40 Watts when you are pushing 400, or 40W when you are pushing 150? My Tacx was about 15% low across the power bands.
• Is the difference affected by flywheel speed? My Tacx was within 1% when the flywheel was below about 25 MPH, but above that and accuracy went out the window.
• Is the difference affected by cadence?
• How did you measure it; are you relying on observation of instantaneous readings, or something else? When I recorded my Tacx issues, I was capturing splits from the two devices at about 5 minute intervals. So, I could collect many data points over a long ride and could see consistent differences over time.
• Is the Stages a single-sided or dual-sided? If you have a 55%/45% left-leg power bias, then your Stages would be reading 10% high.
  

Is it a single or dual sided PM? My pedalstroke as analyzed by Garmin was 49%/51% so one would assume not much discrepency but when i unpaired the dual meter to use on 2 bikes the left side read higher at the same effort than the right by 25-30 watts.
When I got my kickr 2018 it's power matches with one Stages crankarm but not the other. I suspect it's the difference in the strain gauge placement on the l/r arms?

I use a powertap on rollers with zwift, I find myself struggling a lot at 260 on kickr at similar rpe to 300 on powertap. PT matches stages close enough, kickr is very low

Could it be that you can move more freely on the rollers so you can put better power out? What indoor cycling platform are you using?
When I had my cyclops trainer I was able to calibrate it in Rouvy freeride to my power meter as there was a discrepency between that and my powertap P1 pedals. Not sure if you can do that with the kickr or not.
I've since then decided that outdoor power doesn't really matter to me that much anymore as I typically don't ride on the road anymore if I can help it and offroad is so variable that i'm not really sure what/if anything the numbers would really tell you. I go with the power from the kickr as to me it's only a number I can use to see what my gaines are.

I am not surprised. Or at least coming from my experience using a Gen1 Kickr from 2014. The last firmware update with the Advanced Spindown got my Kickr within 2 watts of my Quarq and remained like that for a long time, but about 3 weeks ago it all went haywire again with the Kickr being 15 watts off from the power meter so I put the PerfPro application back to using power meter control to override the kickr's power and let the power meter govern the workout. So I am back to being happy again.

Looks like Zwift has the same option as does TrainerRoad as well. So if you cannot get things synced up there is that option.

https://forums.zwift.com/...implementation/12645