This product is as advertised.. it attempts to calculate “power” based on heart rate. I would actually say a better term is it measures “effort” and translates that to power. This product can be used as a great tool to compare efforts across an individual, but is definitely not to be mistaken for a true power meter.

I was really confused with how it could possibly work, but basically it uses heart rate VARIATION and probably the actual number to come up with a power value based on an algorithm developed by analyzing hundreds (maybe thousands?) of data files from various athletes to correlate heart rate + variation to actual power. When your heart rate goes up, you will see your power spike, when it is going down, you will see the power go down and even down to zero as your heart rate continues to drop. If Garmin is able to come up with their own algorithm, I think they could essentially make this product obsolete… they could do the calcualation within a head unit, like a garmin 500, and also use way more variables (speed/grade etc.) to come up with a great algorithm that would probably be way more accurate.

I naturally have a heart rate on the higher end of the scale during intense exercise(I can average near 180 for 2+ hours), and I believe my power is exaggerated with this device with what is actual. However, using this device as a training tool, I can compare my efforts across rides and see improvement/gauge how hard I went. This device is much less useful during a ride, except to maybe see the average power over the entire ride. I have found the 3s and 5s average power to even be useless, since it jumps around way too erratically to try to use that as a pacing guide. The overall ride average power though will at least give you some idea of how hard you have been going. Since the feedback is not immediate, it is particularly not a good tool for short intervals, although maybe for longer 10-20min efforts, using a lap average might come in handy.

I did take this device on a ride where I essentially “blew up” with cramps during a very hot ride, and my heart rate was sky high until I was able to get back to sufficient hydration. I would say that this device was definitely very inaccurate during this time, as I could barely turn over the pedals, yet the power was still very high due to my heart rate being abnormally high for the power I was putting out due to the environmental conditions. Which is why I approach this device more of as an effort meter at times, than a power meter.

Overall, I would say this product, for it’s cost, is a great addition if you aren’t looking to drop the k-2k for a true power meter, as an introduction into training with power. I would equate it to a heart rate monitor on steroids. But I would weigh its limitations in your decision for purchasing. If you need to use it for pacing purposes, I would say using straight heart rate might be better for pacing (and of course a true power meter will trump all), while using a long average of the power (10m-20m) might give you some indication of effort. However, 3s-5s power for pacing with this device is pretty useless since it is not consistent and has way too much variability.

PROS:
Great introduction to training with power
Heart rate monitor on steroids
Cost (compared to alternatives)
Nothing like it on the market

CONS:
Useless for short intervals (due to heart rate lag)
Bad 3s/5s power data, can’t be used for that type of pacing
If your heart rate is behaving abnormally due to environment/extreme fatigue, expect numbers to be off also

I’ve ridden the Cycleops powercal with a Garmin 500 for the past 3 weeks and so far I am very happy with my purchase. I’d ridden with a wired powertap over the past seven years and the powercal is within 5 watts for a 20 minute effort. I wouldn’t imagine it being very useful for short intense efforts but it seems to be a great value for measuring longer intervals. Since it is a heart rate based system there are some limitations but overall I am satisfied.

I am fairly surprised at how accurate this unit is, based on the fact it uses heart rate and no calibration. It is fairly consistent, so if it is all you are using to gauge your workouts, then it is worth the money. If you are comparing your numbers to more accurate numbers then it will not be totally on the mark.
I have done a side-by-side comparison of this unit with the Kinetic inRide on my Road Machine Trainer(accuracy +/- 1%) and the Powercal is usually about 10 to 12kW below the inRide for the Avg power of a workout. Not too bad.
One other thing I noticed that when your heart rate doesn’t increase as normal for a given workout(usually a sign of overtraining and time for recovery), then the power measure is affected as well and the readings are lower than normal. Makes sense since it is based on HR. Where with a real power meter the power would most likely be higher(considering you are working as hard) and just your heart rate would be lower.
Now that I have a baseline for this unit from comparing it with my inRide trainer, I can transfer that to my outdoor rides without a very expensive power meter. So if you want power with a little less investment this may work for you.

If you want more details and see the numbers, check out my blog article here… […]