How to Choose the Right Cycling Power Meter for You

By Jim Rutberg,
CTS Pro Coach, co-author of “Ride Inside“,
“The Time-Crunched Cyclist”, and
“Training Essentials for Ultrarunning”

A cycling power meter is one of the best training tools a cyclist can invest in. A power meter offers a way to directly measure the work a cyclist is performing in real time. It is hard to overstate the value of direct measurement. Coaches and athletes in sports, including running and swimming, and team sports on courts and in stadiums, would kill to be able to measure workload as accurately as cyclists can.

Power Meter Basics

The best power meters use strain gauges to measure minute deflections in cycling components as the cyclist pedals. Therefore, power meters are typically integrated into crank spiders, crank arms, and pedals.

Power output is expressed in watts and calculated using the following equation: Power = Force x Velocity. More specifically for cycling, power is the product of torque (force acting on an object to make it rotate) and cadence (pedal speed). Power meters also reveal the mechanical work produced a cyclist produces, expressed in kilojoules. This is important for estimating energy expenditure.

Power Meter Types and Training with Power

For a detailed look at how to train with power, the benefits of training with power, and the pros and cons of crank spider-, crank arm-, and pedal-based power meters, see our “Essential Guide to Cycling Training with a Power Meter”.

Choosing the Right Power Meter for You

There are a lot of power meters on the market, so here’s how to evaluate your choices choose the power meter that best fits your riding style and performance goals.

Direct vs. indirect measurement

The first step to making a choice is to make sure any meter you are considering features direct power measurement. Strain gauges are the best way to measure power because you are directly measuring the deflection caused by applying force. Some power meters try to calculate power from indirect data instead of strain gauges. Although these devices are more affordable, their accuracy and consistency are more affected by external variables than strain gauges are. And with the prices for crank arm-based power meters coming down to the same ballpark, the value proposition of crank arm-based power meters makes more sense.

Accuracy vs. consistency

You also have to consider both the accuracy and consistency of your data, and understand the difference between them. An accurate meter measures power within 1.5% of the actual power you are producing, but consistency is ultimately more important than absolute accuracy. Even if your meter measures 2% lower than your actual power, it is important that it measures 2% low today, tomorrow, next week, and next month. Consistency is ultimately more important than absolute accuracy because it enables you to monitor your training and track your progress with confidence.

Thanks to improved technology and a highly competitive market, almost all modern cycling power meters (with strain gauges) provide consistent measurements. However, as coaches we often (more often than not) see discrepancies between the power numbers recorded by different power meters used by the same athlete. These may be minor and easily accounted for, but sometimes they are significant enough (e.g. 10% difference from one power meter to another) that it affects the power zones athletes use on different bikes.

When you decide to purchase your first or next power meter, you still need to choose to measure power at the crank spider, crank arm, or pedal. Here are some considerations to help you make your choice:

Compatibility

Before buying a power meter you must make sure it’s compatible with the rest of your equipment or that you can purchase additional components to make it compatible. For instance, crank spider-based power meters like SRM, SRAM, and Rotor have 4 bolts or 5 bolts, and the “bold center distance” or BCD may be different than your bike’s original equipment. This may require purchasing new chainrings to fit the power meter crank.

With pedal-based power meters, check to make sure the required cleats are compatible with your shoes. Road pedals (Garmin Rally RS and RK, Favero Assioma) use three-bolt cleats. Wahoo PowrLink Zeros use a 4-bolt cleat that has an adapter for 3-bolt shoes. Off-road pedals (Garmin Rally XC, SRM X-Power) use 2-bolt SPD cleats.

Batteries

Almost all modern cycling power meters are either rechargeable or use athlete-replaceable batteries (e.g. coin cell, AAA, AA). Dual-sided pedal-based power meters will need batteries in both sides you’ll need to plug in both pedals to recharge. And although manufacturers have developed tight seals for battery compartments, replaceable batteries do introduce greater possibilities for water intrusion. From a cost/convenience standpoint, you’ll either be purchasing batteries for the lifetime of your power meter or you’ll need access to electricity to keep your power meter charged.

Portability

Many athletes train on more than one bike and ideally you would train with power on all of them. On a scale of time and tools required, swapping pedal-based power meters is probably the most convenient. Swapping left-side crank arm power meters (e.g. Stages, 4iiii) can be reasonably quick once you get the hang of it. Swapping crank spider-based power meters can be done but is rarely pragmatic. First, it only works if the bottom brackets are the same across bikes. Second, the chainrings across bikes – like a road bike vs. gravel bike vs. cyclocross bike – might not be the same.

From a practical standpoint, I make the following recommendations. If you ride multiple bikes (gravel, road, MTB, cross), a MTB-pedal power meter is ideal. Yes, you’ll need to wear MTB or gravel shoes while riding your road bike, but new MTB shoes are light and stiff (and easy to walk in). If you only ride in road shoes and/or travel frequently, road pedal-based power pedals are a good choice. They’re easy and quick to swap and you can pop them onto a rental road bike or even a hotel exercise bike on a business trip. In practice, athletes are less likely to swap crank arm- and crank-spider power meters from bike to bike, even when it’s possible.

Durability

No product lasts forever, but modern power meters have a great track record for durability. Even so, it is good to at least think about long-term wear and tear before making a purchase. Crank-spider power meters are probably the most durable of all options, followed closely by crank-arm meters. Power pedals are quite durable but suffer the normal wear and tear you find with any pedal system. The bearings and seals in the spindles wear out, and the contact surfaces wear down. Of all options, pedals are most susceptible to impact damage if you crash or smack your into the road or against a rock.

5. The Big Picture

A power meter is a long-term investment in your progress as an athlete. There will always be a cheaper option, but in the long run athletes are best served by shopping on value over price. After 20+ years of training athletes with power, the value you are paying for is the years of testing, product refinement, and quality control. And don’t underestimate the value of buying from an established company with the customer service and production infrastructure to be responsive to customers’ needs. With power meters it doesn’t always pay to be an early adopter of the newest tech. If high quality data and durable manufacturing are high priorities, you’re more likely to be frustrated by the quirks and data drops in early-stage products.

CTS Power Meter Recommendations

CTS Coaches have been working with power meters since the early days of SRM. We used Powertap hub-mounted power meters when they existed, and we currently work with athletes using all types of power meters. Our top choice is a spider-based power meter for accuracy, consistency, and reliability. Our next choice is a pedal-based power meter because the accuracy and consistency are very good and they are easily transferred between bikes. Crank arm power meters are good value choices. And smart trainers and smart bikes are great additions to anyone’s arsenal of training tools.