Love them or hate them, when it comes to tech controversy, power meters are right up there with disc brakes on road bikes.
However, there’s no denying the benefits of riding with power data. Knowing your numbers enables you to track and measure your performance, and ultimately improve it.
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Used wisely, a power meter can ensure you get the best out of every ride, help you work towards specific goals, and most importantly, when to rest and recover.
What is a power meter?
A power meter is a device fitted to a bike that measures the power output of the rider.
Most commonly, power meters use strain gauges that deflect slightly when a force is applied. By measuring this torque and combining it with angular velocity, power (measured in watts) can be calculated.
If you want to get the most out of your training then a power meter is the best tool to quantify your workouts.
As ever, there’s no single power meter that is the best. This will depend on how you intend to use it, your bike, your bike placement options, your budget and if you want to use it with more than one bike.
We’ll start this guide with our immediate product recommendations, and then we will provide you with an in-depth guide into understanding more about one of the most important technologies in cycling.
How does each power meter measures power? What does power actually mean? How it power calculated? These questions are answered below and there’s even a helpful link to help you get the most out of riding with power.
Best power meters reviewed 2020
You may notice that the majority of our favourite power meters are crank based. We’ve found many of these to be reliable – while others, pedals in particular, can be a bit vulnerable in poor weather. Hub-based options have proven themselves hugely reliable, too, but they do limit you in wheel choice.
We’ve included some of what we think are the best examples below. With each product is a ‘Buy Now’ or ‘Best Deal’ link. If you click on this then we may receive a small amount of money from the retailer when you purchase the item. This doesn’t affect the amount you pay.
PowerTap G3 Hub 9/10
Read more: PowerTap G3 hub review
Hub-based power meters have been overlooked a bit in recent years, their lack of popularity largely comes down to the way they limit wheel swapping between training and competition. However, the G3 from PowerTap is a hugely reliable piece of kit.
We’ve really rated this version, and as fans of Power Tap for many years, we can speak highly of its overall reliability. Battery changes can be a bit fiddly, but that means the unit is incredibly watertight – which results in next to zero problems. It’s a shame you don’t get left/right power but not a deal-breaker.
The hub weighs 325g, so it does add a bit of weight in an uncomfortable place at the rear wheel, but it’s not a huge price to pay for detailed and trusty numbers.
Quarq DZero DUB Power Meter Spider 10/10
Read more: Quarq DZero power meter review
A winner in our 2019 Editor’s Choice awards, the Quarq proved to be accurate, durable and reliable, without being anywhere near one of the most expensive on the market.
It’s good to know that while we tested the carbon version, there’s also an alloy Quarq DZero power meter for nearly half the price.
Our tester escaped dropouts and power spikes during testing, and found the data reliable – reading about four watts above a Wahoo Kickr, which is a reasonable number accounted for via drivetrain losses.
The Quarq DZero is a solid unit for those seeking easy, reliable, and accurate numbers from a power meter.
S-Works Power Cranks 10/10
The S-Works cranks from Specialized come fitted to some of their top-end bikes, pre-installed, but the unit is available aftermarket, too.
Specialized has used the technology created by 4iii – but it has housed it within its own external crank, with a major focus on ensuring sufficient waterproofing. The strain gauge is within two black pods, on the inside of the cranks, which make these duel sided and weigh just 15g.
We found the unit reliable and didn’t suffer with dropouts or power spikes, with the whole experience close to flawless. The only downer was that crankset installation was a bit fiddly.
If you find the price tag of the full carbon S-Works version a tad out of your price range, it’s good to know that there’s also an Ultegra version for under half the price.
Shimano Dura-Ace R9100-P power meter 8/10
Read more: Shimano Dura-Ace R9100-P power meter review
Shimano’s first crack at a power meter is a reliable and easy to use dual-sided meter that looks the business.
We’ve listed it in our ‘best of’ guide because it’s an option under high demand. Touches like the USB recharging port are great, and tester Richard Windsor found it was easy to calibrate and change batteries.
Being a first-generation, it did expose some flaws, but we’d expect some of its issues to be rectified through updates. For such a high price, it’s worth considering if other options might suit your needs and save you some cash, too.
FSA Powerbox power meter 9/10
Read more: FSA Powerbox power meter review
With its comprehensive range of chainrings, a power meter is a natural extension of its product portfolio for FSA. It paired up with German power meter experts Power2Max to develop the Powerbox crank-based power meter.
We got hold of the alloy FSA Powerbox for our test, but there’s also full carbon versions available too, although expect to pay about double the price.
When we tested the Powerbox, we found that it was accurate and reliable and also coped well with the odd dousing with a hose pipe. It’s ANT+ and Bluetooth compatible, comes in carbon and alloy versions and with a wide range of chainring size options, including supercompact options.
Favero Assioma Duo Pedals 9/10
Read more: Favero Assioma Duo Pedals review
These pedals provide reliable numbers for the entirety of the testing period and didn’t have any problems connecting to the head unit, computer, or the companion phone app. The pedals are USB rechargeable via a magnetic connection, meaning no fiddling with rubber seals and ports.
The pedals provide some novel metrics, such as the amount of time you’ve spent pedalling out of the saddle and your platform offset – the degree to which you pedal with one side of your foot. More common metrics such as left-right balance are also present, although a cheaper single sided version is available which doesn’t have these capabilities.
Stopping the pedals getting a perfect 10/10 is the unfortunate pedal weighting, which does make clipping in and out a little more difficult than with other systems. If fast-starting crits are your thing, then that might be a concern. The Look cleat system is used on these pedals.
PowerTap Quarq P2 power meter pedals 8/10
Read more: PowerTap Quarq P2 power meter pedals review
PowerTap’s P2 pedal gives an accuracy rate of +/- 1.5% and when we tested the P2’s they proved to be a reliable training partner, with no data issues after 50 hours of riding.
These power pedals are not the lightest out there, weighing in at 398g with batteries—but the added weight comes in the form of a robust and sturdy design.
The P2 pedals also incorporate a strong rubber seal as further weatherproofing and this always sat flush.
4iiii Precision power meter 9/10
Read more: 4iiii Precision power meter review
4iiii has delivered a reliable and inexpensive left-side crank that only adds 9g to the weight of the crank – including the battery.
It only measures left leg power, but with the 4iiii Precision, you can adjust the scale factor to account for a known imbalance in your power output between your legs.
Our testing found that it is sufficiently accurate and consistent, and we experienced no issues with regard to water ingress.
What are the different types of power meters?
Currently, power meters can be placed in five key areas of a bike. Of course, each has their own advantages and disadvantages.
Hub-based systems such as the PowerTap G3 are amongst the most simple power meters on the market. With fewer forces acting on the strain gauges, many engineers regard the hub as the most accurate location to measure power.
Power measurement will be slightly lower here than on a pedal or crank system as you’re measuring what is left, post drivetrain losses. It also means your power output can be a bit lower if your drivechain is very dirty.
Bottom bracket systems can be accurate and low maintenance. However, installation is more difficult and is made all the more complicated by the varying bottom bracket standards available today.
Factor in that a system of this type may not fit your bike and it is also likely to mean you have to run a different brand chainset to the rest of your groupset. Examples include Rotor INPower.
Chainring based power meters can be very accurate but it is worth factoring in that they don’t actually measure individual left/right power, although they can estimate it.
Similar to bottom bracket systems, they are not as easy to swap between bikes, unlike pedal-based systems, and there can be compatibility issues. Examples include the fabled SRM (the most popular choice amongst pro riders), Power2Max and Quarq.
Crank arm-based systems can be relatively easy to swap between bikes, too. Like pedals, they have the potential to be single or double-sided and popular examples include the Stages crank arm and 4iiii precision meter.
Pedal-based systems are easy to fit and change between bikes, but can be less accurate owing to the complexity of the force measurement. What’s more, being exposed makes them at greater risk of damage.
Single, double and combined power meters
Single-sided power meters
You can buy single-sided power meters that measure power from one side, usually the left, and then double the reading to estimate your total power output from both legs.
A single-sided only measurement means doubling a single legs power may not be a fully accurate representation of your power, but it can mean they are more affordable.
It may be worth checking if you have significant imbalances before opting for a single-sided meter. Note a 48/52% balance between legs is common.
Combined power meters
These units effectively combine the power from both right and left legs and do not measure it independently. An example would be a PowerTap G3 hub or SRM.
Note that these systems, although accurate, will not differentiate which leg the power comes from.
Left/right side independent measurement
This is found on more modern and more expensive power meters that have gauges in multiple locations, such as pedals and some crank-based units.
This can be useful in establishing if you have an imbalance (one leg much more powerful than another) and for working on pedalling technique. It can also be used if you are recovering from a single leg injury.
This is limited to power meters that measure power in more than one location, such as pedals, but also more expensive crank-based units, like Rotor 2InPower.
Power meter connectivity
Everything rated here and the vast majority of power meters transmit via ANT+, allowing them to connect to most bike computer systems, including Garmin.
Newer power meters are also offering Bluetooth Smart connectivity – a handy tool for connecting to smartphones or updating firmware.
Power meters explained
The math: power (W) = force x distance / time
Watts are the energy required to a move a mass a certain distance in a known time period. 1W = 1Nm/s in other words to move one Newton one meter in one second costs one watt of energy.
So in bike speak, the mass is you plus your bike, and the distance is the ground covered.
Moving a bike, though, is a far more complicated scenario, as its resistance to motion is far from consistent. In layman’s terms, then, this equates as: power = force x velocity
And that is the key to understanding how a power meter works. It’s essentially applying that equation to a given part of the bike – be that BB axle, crank, hub, pedal axle etc.
Accurate measurement of this force is one of the biggest challenges power meter manufacturers face, placing the upmost importance on the smallest of details such as the placement of the gauges, the quality of the gauges themselves and even the temperature of the measured material.
How much do power meters cost?
Entry level – typically £250-£400/$300-$500
At this price you are likely to get a single-sided measurement that doubles the reading to estimate both legs. PowerTap hubs are also available at this price, as are Stages 105 crank, the Powertap Hub and the Vector 3.
Mid-level – typically £550-£800/$700-$1,000
Mid-price starts to see pedal-based systems and dual-sided meters. Crank and chainring systems also become available. Professional athletes are increasingly using meters at this price point. PowerTap P1 Pedals is a fine example.
Top end – £900/$1,200 +
At the top of the market, we find dual-sided measurement and crank and spindle based systems. Examples include the Rotor 2InPower.
How to use a power meter
If you want to learn about how to ride with a power meter, click on the link here.
It has lots of useful information about how get the most out of your gadget and how to apply the numbers to your training.