Originally Posted by
Branko D
Within 10% of actual watts is good enough for determining how hard you were trying, really. I don't have a power meter on my latest bike, so when I'm training on it based on perceived effort it tells me if I've paced it near correct or not.
The problem with estimates is that you don't have one real-time, which makes it of very limited utility. If you could get a 3s or 5s average estimate which is within 10%, you could pretty much train and pace off that, wouldn't be ideal, but still more useful than, say, looking at heart rate. Seeing an estimate after the ride, eh, not terribly useful.
The point, that I usually see made about this anyway, is if you're OK with plus or minus 10% on your training zone you can do that with perceived effort or heart rate, without needing to be concerned about a power number. Hence the conventional wisdom is that power measurement is *only* useful for precise, real-time training metrics, and the *only* way to do that is with an actual strain-gauge power meter.
I don't necessarily agree with the conventional wisdom - I think that knowing a little bit more about what you're doing or have done is generally a little bit better than knowing a little less. ie, Strava power estimates can be useful, just not in the same way as they use their power meters.