Intervals vs Garmin Connect watt difference

Had 4 hour race yesterday. Garmin Connect gives 10w higher average (247w vs 237w) and 7w higher NP (297w vs 290w) than Intervals.icu. Can’t figure out why, my Edge 530 has zeros included in the average and has the same number as Connect, Strava on the other hand agrees with Intervals. Only auto-pause was few seconds just before the start, no stops during the race. Anyone got an idea for the reason? Probably not a bug, but that was maybe closest category.

I don’t know why there should be a difference. The average power is the total work done in Joules / recording time (removes long stops) or elapsed time (if recording time not available).

I opened the fit file in filefileviewer.com and the average power for the session is 247w. Intervals.icu doesn’t use those and recomputes most things from the underlying data so it can support editing of power and so on.

Using the Intervals.icu Joules of 3612519 and elapsed time or timer time from the fit file gives 236 or 237 watts average. So it’s likely the Joules number that is different. Those numbers are calculated on the device (AFAIK) so maybe some power readings didn’t make it into the file but were counted somehow? Intervals.icu interpolates the power stream to 1 second per tick.

Maybe this is like laps from the device that never quite match up with the underlying data?

Thanks for the reply. Yeah, its not a big deal but found it interesting, difference is surprisingly big. Little googling led me to Garmins forum where somebody had same kind of findings.

https://forums.garmin.com/sports-fitness/cycling/f/edge-530/225864/average-power-discrepancy-in-garmin-and-strava

Looking back at older rides it seems like the difference comes up especially when racing, when the power is more on/off, maybe the poster on the garmin forum is on to something. Numbers seem to match better when riding in a smoother manner.

Thanks for finding that.

The 186 value is computed using the accumulated power value reported by the power meter.

Maybe that is what is happening in your case. Not much I can do unfortunately.

Could be, thanks anyway!