I’ve estimated mine to be 225 based on hour-long high-effort rides on my CycleOps Fluid2 trainer and its published power curve.

I’ve done numerous outdoor rides where my Normalized Power (with a 4iiiii Precision 3, left-side power meter) were 215-220, so I think my estimate is good enough for calculating zones and using them for training.

One of these days, I’m going to do an actual FTP test on my trainer….