Great question! Using only the snap, I noticed at times I would fail a workout in the 1st 10 min, and other times it would be incredibly easy. That was my first clue that there was a consistency problem. I bought favero pedals and sure enough the power was off by a ton. My girlfriend also bought a power meter (4iii) and she is seeing the same differences in power. I haven’t tested it yet but 4iii and the favero are very close to eachother based on how much higher each are relative to the kicker snap.