The power meter has been around in the pro peloton for over 30 years but has only recently become de rigueur among amateur riders wanting to train more clinically and race more effectively.
The made-to-measure nature of the power meter takes the guesswork out of your training and allows you to accurately track fatigue and fitness – valuable parameters for monitoring training load and consistency.
Over the past several years, power meters have become more affordable thanks to advances in technology and the introduction of a host of new competitors to the fray. There are several types of power meter configurations available, namely those of the hub, spider, crank, pedal and bottom bracket variety, but choosing the right one comes down to four factors: price, compatibility, accuracy and weight.
What are power meters?
As the name suggests a power meter is a compact electronic device that calculates power by way of a strain gauge. The strain gauge transduces flex into electrical resistance based on how much strain or torque is applied and multiplies it by the angular velocity (cadence) to calculate power, which is measured in watts. Sounds complicated, right? Thankfully, your cycling computer does all the maths for you, processing the data it receives from the power meter via an ANT+ or Bluetooth connection. That said, not all power meters are created equal – the accuracy and reliability of each unit hinge around a number of complex parameters, the most pertinent being the quality of the materials used in its construction and number of strain gauges fitted. As you can imagine, manufacturing such a device is an intricate process which explains why these components cost as much as they do.
Scroll down to see Cyclingnews’ selection of the best power meters available to buy.
Power meters explained
It’s easy to get overwhelmed by the marketing jargon and complex specification sheets when shopping for a power meter. There are five distinct power meter types based on where it’s fitted to the bicycle, so it’s important to factor in compatibility before making a decision. (Most manufacturers have compatibility charts on their website).
1. Rear hub power meters
Hub-based power meters are some of the most affordable, reliable and compatible units available. PowerTap is the main protagonist in this segment and its G3 hub has earned a reputation for its hardy and bullet-proof nature. One of the many benefits of using a hub-based system is the convenience of swapping it between bikes. Compared to other power meters, the location of a hub-based unit may result in marginally lower power readings owing to drivetrain losses.
2. Crank arm power meters
Stages Cycling brought affordability and reliability to the market with its left-side crank concept in 2012. Weighing just 20 grams it redefined the segment with a catalogue comprising a range of crank arms in both aluminium and carbon fibre guise. Since then, 4iiii Precision has jumped on the power bandwagon with its off-the-shelf, left-side Shimano crank arms. (Power pods for other models can be retrofitted as a ‘factory installation’). Crank-based power meters are extremely light and affordable but be wary of frame clearance issues on certain bikes.
3. Bottom bracket power meters
The bottom bracket power meter is not as popular as other designs as it is more difficult to install and isn’t compatible with all bottom bracket systems. But the results don’t lie: Rotor claims its INpower units are 99 per cent accurate (variance of 1 per cent). Another benefit is that the power meter’s innards, battery and electronics are housed within the bottom bracket for added protection and weight balance.
4. Pedal power meters
Not only are power pedals easy to swap between bikes but the plug-and-play nature nullifies the need for complex fitting procedures. Available in two distinct guises: single- or dual-sided, it’s the latter which can independently measure left /right power as well as calculate pedal smoothness and efficiency. The only pitfall stems from the extra weight of the electronics, strain gauge and battery pack located within the pedal assembly. PowerTap, Look, Garmin and Favero Assioma are the chief players in this segment with little between them in terms of performance and reliability.
5. Spider/chainring power meters
Spider-based or chainring power meters rose to prominence in the late 1980s with SRM who pioneered the concept. Available in various shapes and sizes these power meters are compatible with most bottom bracket and chainring BCD patterns and can be purchased individually as a spider or complete chainset. Leading products here come from brands such as SRM, Quark and Power2Max, each of which offers varying price points, weights and power-measuring functionality.
The best power meters you can buy today
PowerTap P2 pedals
The most versatile and easy-to-fit power meter on the market
Weight: 402g (actual) | Battery life: 80 hours | Battery type: AAA | Measurement: Dual-sided | Type: Pedal
The PowerTap P2 pedals require no fancy tools for fitment and can be swapped effortlessly between bikes. Not only are they 34g lighter (400g a pair) than before they also boast a 20-hour battery life improvement over its predecessor (80 hours in total). While they may not appeal to everyone in terms of visual clout (the black P1 pedals are far sexier-looking items) the pedals are appreciably easy to clean and don’t hold much in the way of dirt or grit, regardless of weather conditions and terrain. What makes the P2 pedals a safe bet is the company’s proven track record in terms of accuracy, durability and reliability.
Stages Power LR Ultegra R8000
A no-brainer for number-crunching cyclists looking to upgrade to dual-sided functionality
Weight: 35g | Battery life: 175+ hours | Battery type: CR2032 | Measurement: Dual-sided | Type: Crank, 165mm, 170mm, 172.5mm, 175mm | Rivals: 4iiii Precision Pro
Stages Cycling made a name for itself when it dropped the single-leg power meter concept at an amazingly affordable price just a few years ago. Known for continually pushing the boundaries in terms of weight and performance the Colorado-based firm has taken things up a notch with the introduction of the Stages LR, a dual-sided power meter with generation 3 internals, a boosted ANT+ and Bluetooth signal (6 times stronger than before) and accuracy to a maximum deviation of only 1.5 per cent. Available in two Shimano-only options, Dura Ace 9100 and Ultegra R8000, it adds just 35g to the crankset.
Weighing just 9g the 4iiii Precision is the holy grail of lightweight power meters; it is also one of the most reliable units on the market
Weight: 9g | Battery life: 100+ hours | Battery type: CR2032 | Measurement: Single-sided | Type: Crank, 165mm, 170mm, 172.5mm, 175mm
Weighing in at a scant 9g including battery, the 4iiii Precision power meter represents the pinnacle of lightweight options on the market. Available as a left-side-only crank-based unit the company claims it is 99 per cent accurate. The product portfolio comprises just three off-the-shelf options in the form of Shimano Dura-Ace, Ultegra and 105, but you can send your own crank directly to 4iiii Innovations to have a power pod retrofitted, something the company calls a ‘Factory Install’. Prospective buyers should be aware of compatibility issues pertaining to crank clearance at the chain-stays; 4iiii Innovations recommends checking this before ordering.
The holy grail of power meters
Weight: from 599g | Battery life: 1400 hours (standard), 100 hours (rechargeable) | Battery type: Rechargeable or Standard | Measurement: Dual-sided | Type: Spider, 110BCD asymmetric
SRM has always been considered the benchmark when it comes to power-meter accuracy - it revolutionised the industry and brought number-crunching to the pro peloton. After producing primarily spider-based power meters for last three decades, SRM recently launched a more compatible three-piece power meter crank system called the Origin which can accommodate a host of frame/bottom bracket setups.
The SRM Origin power meter comprises crank arms, a spider (110 or 104BCD) and spindle (BB30 and 24mm), and is available in both carbon or aluminium guise, the latter of which is available with a crank lengths of between 160-175mm. The carbon version was developed alongside Look, with a Trilobe pedal insert allowing for an adjustable crank length; 170, 172.5, and 175mm. SRM claims accuracy levels of 99 per cent.View Deal
Favero Assioma Duo pedals
Accurate and affordable
Weight: 296g (actual) | Battery life: 50+ hours | Battery type: Rechargeable | Measurement: Dual-sided | Type: Pedal
Favero Electronics may be a newcomer to the power-meter realm but the Italian manufacturer has taken the fight to PowerTap and Garmin by offering a lighter, cheaper and more accurate power pedal - the Assioma. In fact, they weigh just 148g per pedal, which is significantly less than the Garmin Vectors and PowerTap P2s (216g per pedal).
It's a tidy-looking package - all the sensors and strain gauges are located in a housing next to the pedal body, which measures directly at each axle. Not only does this neat little design cue ensure the Assiomas look like an ordinary pedal and not as chunky and bulky as its rivals, but it also keeps the electronics from getting damaged by falls or impacts, meaning it's easier to maintain down the line. They're also IP67 certified.
Unlike other power meters that harvest data based on the angular velocity of the crank arm through each rotation, the Assioma uses an instantaneous angular velocity (IAV) measuring technique thanks to an on-board gyroscopic sensor. According to Favero, the IAV way of harvesting data is class-leading, with accuracy to a maximum deviation of only one per cent.View Deal
If you’re looking for a durable and reliable spider-based power meter, look no further
Weight: 172g 130BCD (spider only) | Battery life: 300 hours | Battery type: CR2032 | Measurement: Dual-sided | Type: Spider/chainring
Like Stages Cycling, Power2Max disrupted the industry by bringing power to the people at an affordable price. Owing to its spider-based anatomy, riders are able to choose from myriad crank options depending on budget, something that’s enabled the German company to gain immense traction and market share in a highly competitive space. Power2Max claims its NGeco unit is a dual-sided power meter although it calculates power at the spider and apportions the left/right ratio based on crank position.
However, it does measure both pedal strokes independently making it superior to those of the single-sided variety that collect data from the left side only.View Deal
Aesthetically, and mechanically, one of the best units on the market
Weight: 142g, 130BCD (spider only) | Battery life: 200 hours | Battery type: CR2032 | Measurement: Dual-sided | Type: Spider/chainring
Quarq’s latest spider-based masterpiece, the DZero, can be ordered as an individual spider or as a complete crankset in either aluminium or carbon. Not only are the strain gauges located within the spider but it also benefits from a built-in accelerometer to simplify function and boost accuracy — with a variance of only 1.5 per cent. The DZero power meter is compatible with all bottom bracket types and BCD configurations and there’s even a version for Shimano-specific chainrings called DFour. The DZero’s biggest selling point is its ability to measure power from both the left and right leg which helps improve pedal efficiency and power balance.
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