I've had my PT for about a month now, but I haven't had the time/motivation to do a 20 min test to find FTP. So I originally just kinda guessed, and was way off and then reguessed based on some early rides and it seemed better. I'm now looking at a ride file from this morning's group ride, which was just under 2hrs total. If I look at a one hour chunk of it, my NP was 17 watts higher (287) than my guessed FTP (270) and my average power was decently lower (234). I was decently tired, but it wasn't all I could give for 1 hour.
So, is my FTP guess good or too low or what? Or should I really make time for a 20min test?
Edit: The entire ride was 256NP, 196AP for 2:05. I slowed down for the last 40mins to ride with my GF.