I’m skeptical of Strava’s estimation. After doing an all-out 30 minute climb (32, actually) yesterday, I got a bunch of threshold notifications… my last Ramp test was in March and it said 336 W. I’ve been training with it at 339 W since July (had a good 20-minute climb then).
I did 359 W for 32:00. In the past 6 weeks, my other bests are 619 W for 1:00, 397 W for 5:00, 388 W for 10:00, and 367 W for 20:00.
Garmin predicted: 349 W
Training Peaks predicted: 350 W
Strava predicted: 364 W!
So Garmin and TP appear to be doing just 95% of best 20-minute power (I’m guessing some rounding error accounts for the 1 W difference), but Strava is doing some very optimistic calculations (99% of 20 minute power!). Perhaps normalized power is being considered? My NP on that effort was 364 W… It’s a mystery!