My power meter numbers don't match my smart trainer numbers. Why?

Power meters and smart trainers measure power in different ways, so it is natural that the power reported from the two sources will differ. Pedal-based power meters tend to be the most accurate, however, the high-end smart trainers now provide power readings that are +/-1%. Here are some tips and tricks to make sure that they match up as best as possible. Please keep in mind that there may still be a gap.

  • Power measured by a direct drive smart trainer may be affected by losses from the drivetrain. A clean chain and clean gears can help minimize (but not eliminate) this loss.
  • Be sure to perform a spindown calibration on your trainer using the trainer's native application. Then be sure to calibrate or do a zero offset on the power meter.
  • Power measured for a wheel-on smart trainer will be affected by rolling resistance, tire pressure, temperature, and calibration. For best results be sure to do a proper warm-up for yourself and your trainer prior to calibration.

What about indoor numbers and outdoor numbers? There's an article here that will help explain what's going on:  Ask the Experts:  Indoor Cycling Power vs. Outdoor Cycling Power.