Power Readings: Powertap P1 vs Stages

From now on I will be using the PowerTap P1 pedals. But before I made the switch completely, I wanted to compare the power difference between the P1 pedals and the Stages crank arm that I have been using for the past two years. To conduct the test I paired my Stages crank arm and P1 pedals to separate ANT+ bike computers. I then calibrated both power meters. I warmed up for a bit, and then spent some time in each of the various zones that I work out most often in. I did my best to lap each device as quickly and as closely together as possible. Here are the results:

Anaerobic Capacity Intervals:

Interval Length: 30s 30s 30s 30s
Powertap P1 458 459 470 455
Stages 444 443 452 446
L/R PWR Balance 49/51 (224/234) 49/51 (225/234) 49/51 (230/240) 49/51 (223/232)


High End Vo2Max Intervals:

Interval Length: 1min 1min 1min 1min
Powertap P1 442 446 445 443
Stages 430 433 434 435
L/R PWR Balance 49/51 (216/226) 49/51 (218/228) 49/51 (218/227) 48/52 (212/231)


Low End Vo2Max Intervals:

Interval Length: 2min 2min 2min 2min
Powertap P1 410 410 411 410
Stages 405 408 409 411
L/R PWR Balance 49/51 (201/209) 49/51 (201/209) 49/51 (202/209) 49/51 (201/209)


High End Lactate Threshold Intervals:

Interval Length: 4min 4min
Powertap P1 379 381
Stages 382 384
L/R PWR Balance 50/50 (189/190) 50/50 (191/190)


Mid Range Lactate Threshold Intervals:

Interval Length: 8min 8min
Powertap P1 355 359
Stages 361 361
L/R PWR Balance 50/50 (177/178) 49/51 (176/183)


Low End Lactate Threshold Intervals:

Interval Length: 12min
Powertap P1 345
Stages 347
L/R PWR Balance 49/51 (169/176)


Cool Down:

Interval Length: 8min
Powertap P1 206
Stages 212
L/R PWR Balance 51/49 (106/102)


All in all I am impressed with how close the two meters are to each at all power outputs. It appears the Stages meter reads higher at lower outputs, and the Powertap P1 meter reads higher at high outputs. Somewhere in the 380-390w range they seem to be in agreeance with each other.

Update on February 18th:

Easy Ride:

Interval Length: 70min
Powertap P1 240
Stages 243
L/R PWR Balance 52/48 (125/115)


6 thoughts on “Power Readings: Powertap P1 vs Stages

  1. One interpretation is also that you are more left-leg dominant at lower outputs, pretty even at threshold and a little more right-leg dominant at above threshold.
    I had a ramp test done last year where the favoured leg also switched through the range and i was pretty even at threshold….

    • That’s exactly what it is. The left leg vs right leg dominance changes in different work loads. On easy spin it can be one leg and hard sprints it can be the other. Stages doubles the left leg power and that why there is a difference. Good thing would be to test your legs with Garmin Vector or something else that measures both legs to see if there is a problem hidden somewhere. I’ve seen guys who discover that they pedal 41/59 which means that at 300W a small rider is missing from their legs.

  2. Hey Lionel, I would race at whatever watt output determined from the same power meter. So if it is a little high, or lower, doesn’t matter so long as I use the numbers matching the power meter. What is going to make my choice, is how easy is the meter/s? Which one has the least amount of time wasted and is more reliable? I have other bike with quarq crank and speedplay pedals. My new bike had no power meter, so I need to decide pedals or crank for it. I am leery of having 2 different sets of cleats to switch between bikes, but the stages only has one side reading. Agonizing over decision.

  3. The (little) imbalance looks like where the difference between the power meters is coming from. The stages reads less power because the left leg is doing less of the work. Impressed that the meters are that close in readings.

  4. Pingback: Capteurs de puissance – Garmin Vector v1 vs Stages Power – Le coin de Patrick

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