power average vs NP

[Wobblydrow]

Hi
When i look at a downloaded file my average power differs to the file my Garmin uploads. I was wondering does the isaac software include or exclude zero power time in the average calculation. my NP values are far closer, only a few watts difference, but aerage power can be 20% off.

Secondly, uploading to Strave gives an "weighted average power" which is typically somewhere midpoint between average power and NP reported in Isaac, do you know how this value is calculated based on the data the PP is sending?

For example, https://www.strava.com/activities/2963967947 has my average weighed power at 164W, isaac has average power at 133w / NP 181w
ibr file attached

12_29_2019_0615_142_km.ibr

(1.79 MiB) Downloaded 168 times

. Or "its all Garmin tech and we dont know" would be understandable

[Velocomp]

Sorry, I have no idea how Garmin or Strava calculates its numbers.

Our "average power" excludes zero power time. NP is calculated with the formulas used by Training Peaks.

[Kcblair]

Ah-hah, I was wondering the same thing too. That's good to know , that Isaac does not include zero power. Makes sense. I have also read, that some other calculations for average power, do , in fact , USE zero power , in average power calc.

[lorduintah]

Garmin offers the option to not include zero power or cadence in the average repotted values of these two parameters. (Not positive it will be true older Garmin computers, but certainly more modern models.)

the Garmin Connect application will report NP and that conforms to the appropriate weighting scheme for these values.

If you read up on Normalized Power and Power Averaging, these are not the same metrics, and unlikely to be the same for a ride. NP tends to reward you for hard work with some lulls in effort (coasting for example.)