Tuesday, February 2, 2016

How to Choose a Power Meter

by Nicolas Theopold

Disclaimer: I work for power2max, manufacturers of power meters, but the views here are my own.

In my last column I made the case for riding with a power meter: a power meter can help you train better, progress faster and execute your races well.

If you are thinking about starting to use a power meter you will have to choose the right one for your needs and budgets. Over the last five years the market for power meters has exploded and we now have a large -- sometimes bewildering -- range of options, all with their own advantages and disadvantages. It make it hard at times to see the forest for the trees and to get the power meter that will serve you well. Of course my views and recommendations are colored by my work, so please see this as a starting point for your research.

What Should I Look For in a Power Meter?
When you go power meter shopping, I’d encourage you to look at the following areas when honing in on that dream power meter of yours:

  • What does it measure? Power is torque times cadence. Some power meters measure power directly, others try to infer it from heart rate or speed. Some power meters measure all the power you produce, others measure one leg and double the measurement. Inferring power and doubling one leg’s power will make your data more noisy and potentially biased.

  • Will it give you precise data all the time? Most power meters specify a precision of ±2%. To achieve precise data your power meter needs to work with the correct “zero offset,” which is what it measures when you don’t apply any torque to the drive train. Temperature changes also affect the zero offset. A power meter that keeps your zero offset precise and that deals well with temperature changes well will give you a good basis for precise data.

  • How easy is it to install, use and maintain? How easy is it to get the power meter on your bike? Is the power meter a simple “get on and ride” model or do you need to calibrate it every time you ride? Can you change the battery yourself when it’s used, or do you need to send it in?

  • Will it last? Some power meters are more exposed to crash damage than others. If you choose a model that has a higher risk of being damaged, what’s the cost of replacement if it does break?

  • How much does it weigh? Most power meters are pretty light these days and add 50 grams to 250 grams to your bike, so weight has become less of an issue.

  • How much does it cost? This one may be the most personal question. In the current market, there are models available that run the budget spectrum.

Overview of Popular Power Meter Types
I won’t focus on individual brands here, but will outline some of the advantages and drawbacks of different power meter types available today.

Spider-based power meters: This method for measuring power has been around the longest. It captures torque between the crank arm and the chain rings. Spider based power meters are overwhelmingly used by pro cyclists.

  • Advantages: Direct power measurement of all your power. Torque measured is effective torque (no additional calculations). The power meter can zero automatically when coasting (dependent on model). Well protected from crashes. Long track record. Ability to change crank arm length.
  • Disadvantages: You’ll need to figure out the right model for your bike before installation. Moving from bike to bike is sometimes perceived as difficult.
  • Price range: $750 - $4000

Hub-based power meters: Hubs were the second major entrant into the market and measure torque in the rear hub.

  • Advantages: Direct power measurement of all your power (after drive train losses). Torque measured is effective torque (no additional calculations). The power meter can zero automatically when coasting. Well protected from crashes. Long track record. Easy change from one bike to another.
  • Disadvantages: Can’t use with existing wheels. Need to commit to training or racing wheels.
  • Price range: $700 (training wheel) - $3000+ (ENVE carbon wheel set)

Crank arm power meters: Crank arm power meters measure the deflection of the crank arm to determine torque, and therefore power. Some models measure one side only, some both sides.

  • Advantages: Easy installation, light weight.
  • Disadvantages: Some models only measure one side and infer total power. Deflection requires calculation to give effective torque. Auto zero not possible (zeroing is only possible when unclipped). Carbon cranks not compatible. Change in crank arm length not possible. Potentially higher risk of crash damage.
  • Price range: $700 - $2000+

Pedal power meters: Pedal power meters are also a relative newcomer to the market. They measure torque through the deflection of the pedal axle. Some models measure one side only, some both sides.

  • Advantages: (Perceived) ease to move from bike to bike.
  • Disadvantages: Some models only measure one side and infer total power. Deflection requires calculation to determine effective torque. Auto zero not possible. Pedal orientation needs to be calibrated. Some crank compatibility limitations. Potential risk of crash damage.
  • Price range: $900 - $2000+

Happy Power Meter Shopping
I hope I didn’t put you to sleep with all the technical details about power meters and wish you happy power meter shopping and of course lots of fun and racing success with your new tool!

Keep the watts up.


Nicolas is a long time Endurance Corner team member. Like many, he has followed the Kona dream and has now also made his passion his job. Nicolas works with for power2max power meters and contributes to Endurance Corner on power meters related topics.
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