CycleOps PowerCal review£85.00

Power estimation from heart rate

BikeRadar score1.5/5

The PowerCal is a strap with an algorithm that converts your heart rate into an ANT+ watts signal. This can then be displayed on compatible computers, such as the Garmin Edge of CycleOps Joule.

On the plus side, it quantifies your effort on the bike, providing a real-time 'wattage' number as you ride and allowing for a full measurement of effort in any number of power software options.

On the negative side, it isn't a power meter. The PowerCal doesn't measure power, it guesses it, and in doing so doesn't provide any realistic semblance of accurate power meter data.

For years, CycleOps has done a great job of providing reliable hub-based power meters at a reasonable cost. The PowerCal is an attempt to bring in some new customers at a very low relative price.

Part of the problem is simply presentation: if the PowerCal showed information called something besides 'watts' it could be more useful. Just look at the Nike FuelBand.

Quantifying effort without a real power meter is tricky. Strava has addressed this with a Suffer Score based on time spent in various heart rate zones. In the parallel field of running, TrainingPeaks has used a Training Stress Score based on time over pace, taking your top-end speed into consideration. And the iBike has undertaken to measure most of the forces opposing a cyclist, and doing the math to spit out a wattage number.

In a number of trials with the PowerCal, we found the 'wattage' numbers to be way, way off, both in the short term and averaged over 90-minute rides. Also, the corresponding summation metrics, such as kilojoules or Training Stress Scores, were also off by about 30 percent compared to files from the same ride with a power meter.

Looked at here in trainingpeaks, the peaks and valleys on the powercal wattage (above) were much more drastic than the actual power output:
Looked at here in trainingpeaks, the peaks and valleys on the powercal wattage (above) were much more drastic than the actual power output:

In TrainingPeaks, PowerCal's number changes were much more drastic

There's no way to adjust anything in the PowerCal's algorithm. Whether you're a 20-year-old fit woman or an 80-year-old man with one leg, the PowerCal spits out the same wattage number based on fluctuations in heart rate.

The concept – quantifying your effort on the bike without a power meter – isn't a bad thing. But the PowerCal isn't a power meter, and shouldn’t be presented as one.

Ben Delaney

US Editor-in-Chief
Ben has been writing about bikes since 2000, covering everything from the Tour de France to Asian manufacturing to kids' bikes. The former editor-in-chief of VeloNews, he began racing in college while getting a journalism degree at the University of New Mexico. Based in the cycling-crazed city of Boulder, Colorado, with his wife and two kids, Ben enjoys riding most every day.
  • Age: 40
  • Height: 183cm / 6'
  • Weight: 82kg / 180lb
  • Waist: 84cm / 33in
  • Chest: 99cm / 39in
  • Discipline: Road (paved or otherwise), cyclocross and sometimes mountain. His tri-curious phase seems to have passed, thankfully
  • Preferred Terrain: Quiet mountain roads leading to places unknown
  • Current Bikes: Scott Foil Team Issue, Specialized S-Works Tarmac, Priority Eight city bike... and a constant rotation of test bikes
  • Dream Bike: A BMC Teammachine SLR01 with disc brakes and clearance for 30mm tires (doesn't yet exist)
  • Beer of Choice: Saison Dupont
  • Location: Boulder, CO, USA

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