Powertap/PowerAgent Watts Discrepancy

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I've been breaking in a new (for me) used PowerTap SL. Only had a few rides with it, but am enjoying it alot, especially seeing how my power spikes into 500W-ish every time I stand briefly to go up a modest incline. I'd never equated how much more wattage even the merest hill required, especially when you're trying to maintain your speed on them.

I've downloaded the data from the two rides into PowerAgent, and was reviewing the data. I noticed that the average power for the ride as shown in PowerAgent consistently discounts the average power as shown on the PowerTap computer, by approx. 30 watts. For instance, on a ride along the beach today, my PowerTap recorded about 220W avg, but the PowerAgent showed only about 190W avg. I played with the smoothing and sampling factors in the software, but I still get the same discrepancy. A review of the intervals of the ride, as shown in the computer, seem to back up the 220W average. Any thoughts as to the discrepancy?

Also, I am, of course, contemplating taking everyone's advice on the forum to acquire the WKO+ software. Is anyone aware of any discounts/coupons on the software? Is the $99 price standard?

Sounds like your powertap give average power without the zero power values?
And the poweragent gives your average power. You can switch your powertap to include the zero power.

Also, I am, of course, contemplating taking everyone's advice on the forum to acquire the WKO+ software. Is anyone aware of any discounts/coupons on the software? Is the $99 price standard?Not aware of specific discounts but it does often get bundled in with other offerings such as buying power meters or coaching.

Sounds like your powertap give average power without the zero power values?
And the poweragent gives your average power. You can switch your powertap to include the zero power.
You just might have nailed it. However, when I do the math, that equates to about 20 minutes of 0 wattage. Typically, when on training rides, I always pedal, even downhill. That would mean that traffic lights (and riding under 6 mph -- decelerating/accelerating from lights and stop signs) took up about 19 minutes. Possible, but didn't seem that long. I'll change my computer setting and see if the values sync up next ride.