Power for Triathletes 2/3: Types of Power Meters

In part 1 of our 3 part series on Power for Triathlon we looked a little at the how and why of Power. In this second installment, we discuss the myriad of choices available in the Power market and some of the pro’s and con’s of each.

There is now a very competitive market for power meters which cater for a wide variety of budgets. Generally speaking (like with all technology) with each increasing price point comes an increase in accuracy, reliability and other features. Power can be measured from several points on the bike and measurements are taken by strain gauges mounted in different places, depending on brand. The various locations include the crank arm, crank spider, pedal and rear wheel hub. Each power meter has its own set of pros and cons. Finding a power meter for your bike inevitably means replacing an existing component and this can become quite expensive.

The entry point in the power meter world has been set by two companies who offer power readings from one leg, which is then doubled to give you total power. This concept allows these units to be cheaper than others on the market and has made owning a power meter more affordable.


Stages offer a left crank arm unit which has strain gauges installed on it. They offer a wide variety of cranks from Shimano, SRAM, FSA and Cannondale. If you have a Stages crank unit then it is a very affordable and simple option to use on multiple bikes as it can easily be transferred. However, many users have expressed concerns over the reliability of the power readings.

PROS – Cheap, simple design and installation, transferability
CONS – Reliability, left handed power only (see below).


Garmin Vector pedals are Look cleat compatible pedals that measure power from the pedal shafts. The data collection and battery packs are contained within a pod mounted on the pedal shaft. The pods are considered by many to be fragile; it has been proven they won’t scrap on the ground though they can be more prone to damage than other power meters. Gamin offers two models, an S version which is only left sided power, and a more expensive two sided power. As this power meter is pedal based, the power meter is transferrable between bikes, provided that you buy a compatible torque wrench to install the pedals. The torque wrench is essential for ensuring correct installation.

PROS – Two versions available, transferability
CONS – Look compatible cleats only, need torque wrench to install and transfer

A caution for power readings from one leg.

Whilst the price point of the Stages and Garmin Vector S power meters is good, the units do present a reduced accuracy compared with more expensive, conventional or two sided units. By only measuring power from one leg and doubling it, the true power contribution from the other leg is not known. It is common for power distribution to vary between 1-2% between each leg. An athlete with increased asymmetries through muscular imbalances could experience even higher inaccuracies using a left sided power unit. An athlete that has an increased distribution of 5%, for example, could see power readings vary dramatically when compared to using another unit.  Consider an athlete riding in a half ironman with a target wattage of 250W. If their strong side was their left, the power readings could be as high as 275W whilst they could be as low as 225W if the left side was the weaker.


The hub based power meter comes from Powertap. This unit allows you to build almost any wheel with power readings starting from the same price point. What were once a rather heavy and costly addition to your wheelset, Powertap wheels are now a reasonable and reliable way to measure power. A power meter in the wheel can be a benefit and also a hassle. It allows flexibility to transfer the unit between different bikes, however, the power meter is built into one wheel, and therefore if you have multiple wheelsets (like training and race wheels) you will need power meters for both wheelsets.

PROS – Price point, reliability, weight, transferability
CONS – Need one per wheelset


Quarq is another brand that has established itself with providing a reasonable price point for reliable power meters. Quarq is a SRAM brand and offers several cranksets with power measurements from the crankset spider. The options offered by Quarq will suit every bike. The brand is also planning to introduce an entry level model with heavier aluminium cranks (compared to the carbon cranks). Quarq’s more expensive models will estimate left and right sided power by making simple assumptions based on power transfer from each leg during different phases of the pedal stroke.

PROS – Reliability, reputation, range compatibility
CONS – Price point for more expensive models


Power2max offer crank spider based power readings. You can buy whole cranksets, like buying a Quarq, but most units are offered to simply replace the crank spider. They offer compatibility to a wide variety of brands but with the notable exception of Shimano because their crank and spider are integrated. The ability to buy only the crank spider does reduce the cost a fraction which makes their offering quite appealing, particularly if you want to keep the same crankset like a Rotor crank. The brand is now onto its second version (Type S) which has made vast improvements on version 1 including accuracy, aesthetics and maintenance. The brand is currently clearing out the remaining version 1 stock thus they are available for a great price. Power2Max also give left-right power readings in the same way that the Quarq models do.

PROS – Range compatibility, price points for both models (particularly Version 1).
CONS – Version 1 not as good as version 2


Quarq and Power2max offer left and right power distribution through assumptions of load distribution through different phases of the pedal stroke. These units assume that when the pedal is between 12 and 6 o’clock it is generating all the power, when in reality there will be power generated from the other leg as well. Infocranks measure power generated in each leg independently and therefore offer more accurate data. The brand advertises that the units do not require calibration to account for temperature and pressure changes, which most other units do require for accurate results. One drawback of the Infocrank units is that they require cadence magnets be set up against each crank arm.

PROS – True power balance data, no calibration required per ride
CONS – Require additional cadence magnets


Pioneer have also entered the power meter market offering independent power measurement from each leg. The brand has chosen at this stage to offer compatibility with Shimano Dura Ace and Ultegra cranksets only. An athlete has the choice of either buying the power meters installed on cranks, or to supply their own set of cranks which Pioneer will install power meters onto. Either way, once installed this unit will capture power readings twelve times across one pedal stroke in each leg. Pioneer also offer a GPS cycling computer which can graphically display each pedal stroke on the screen, thus showing a rider their pedalling efficiency.

PROS – True power balance data, pedal efficiency with Pioneer cycle computer
CONS – External installation and servicing


SRM is widely accepted as the gold standard for consumer power meters. It is a crank spider based power meter and is often the preferred unit within professional cycling. SRM units are highly regarded for their German build quality and they claim to give an accuracy within 1%. As a result of their reputation, build quality and accuracy, SRM units are the most expensive on the market. They will trust no one else to recalibrate and service their units, and thus you need to return your power meter to SRM every few years for a recalibration.

PROS – Build quality, reputation, accuracy, external support for recalibration
CONS – Price, external support for recalibration

So many choices…

The above list is a good summary of the power meters that are available on the market today. It’s easy to become confused about which model is best suited to you. Ultimately factors like budget, current equipment and sporting level will heavily influence your choice. In some ways it’s almost like buying another bike as it can become just as expensive, adding more confusion. However, the primary focus when deciding on your power meter should be buying a unit that gives reliable total output power data as this is what will help you to train and race. At the end of the day an athlete’s power output, just like heart rate, is a measurement that is unique to you.

Thomas Bruins is Front Runner Sports Triathlon and Technical Consultant. An engineer and former 2012 Oceania Elite Duathlon Champion and World #5, Thomas offers you power testing on your bike, Anaerobic Threshold Testing, 1 on 1 skills and coaching and personalised training programmes delivered via Training peaks platform. Find out more www.frontrunnersports.com.au or email triathlon@frontrunnersports.com.au