eFTP Indoor trainer vs Power meter

Got some questions… I am new to the whole powermeter thingamajigg and a little lost in numbers…

This winter I mostly rode indoor on my cheap Taxc Flow (on Zwift). It does give power values, so - that’s nice. I heard several times the numbers of the taxc are constant but that it tends to overstate power.

Did ramp tests that showed quite high ftp numbers - 226W FTP was the last number I got. I set the ftp manually to 180 (yes, that’s basically an arbitrary number but it just felt OK) because 226 was way too high for my feeling. Might also be that I’m not used to this training intensity…
I don’t ride a lot, am not the fittest person in the world: 2020 I rode 2800km total which was the highest distance I ever rode in a year…

On the aforementioned last Ramp Tests on Zwift with the Taxc Intervals.icu set an eFTP of 208.
A few weeks ago I came across a used stages (left only) powermeter that I bought. As of now, I’m getting back to riding outdoors.
On my last outdoor ride using the stages intervals.icu states an eFTP of 209W. As I don’t do races, (I ride just for fun but enjoy playing with numbers) the ftp is not really important to me, but it is of interest.

What I don’t get: Is the eFTP based on one ride? On one effort? On the last few rides/effforts? Can I see which one? Can that be adjusted? And is there a possibility to fix power numbers based on a perdentage? P.E. doing a ride on the trainer recording both the stages and the tacx power numbers and put an offset to the existing rides done on the trainer?
I know that the stages doesn’t give me the most acurate numbers, but I’m shooting for consistency for the winter rides.

Is the eFTP going to correct itself over time? How long does this take? Should I just keep on riding and basically ignore the winter season’s numbers on the Taxc?

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The continuously updated eFTP number is calculated from a single max effort that is long enough. It gradually decays if you reduce training load. So the activity with the “FTP Up” achievement is the one that bumped it up. You should probably just use it as your FTP.

If you get sick or injured and know your FTP has dropped a lot then you can reset eFTP to a lower number manually so you get “FTP Up” achievements again (add calendar event “Set eFTP”).

You can scale power numbers for an activity. Click the “Actions” button at the bottom of the ride timeline chart. But I wouldn’t fiddle with that until you are pretty sure one of your power sources is way off.

So yes I think you should just keep riding and see how it goes.

Thanks a lot for your help. I will just keep riding, then. :slight_smile: