If you want to get the most out of your training, assess your cycling performance in greater detail or most importantly improve your performance, then a power meter is the piece of technology for you.
Power meters have been used in the pro peloton to monitor a cyclist’s performance for many years, but has only recently become more available and affordable to the every day cyclist.
There are several types of power meters configurations available to purchase, which vary in price and how the power measurements are taken. Power output can be measured at the crank spider, crank arms, bottom bracket, pedals, rear hub and nowadays, even with a unit that connects to the handlebars.
When choosing the right power meter for you, it all comes down to the price, compatibility, weight and accuracy of the unit.
If you are looking to buy a power meter, we have compiled a list of the best and most popular power meters that are available to buy.
What is a power meter?
A power meter is an electronic device which is attached to a bike, measuring the power output of a rider (in watts).
Power data can be sent to any Bluetooth (low energy) or ANT+ compatible bike computer or smartphone.
A power meter can be attached to a crank spider, crank arms, bottom bracket, pedals, rear hub and nowadays, even with a unit that connects to the handlebars.
How does a power meter work?
Most power meters measure torque by using an incredibly small electronic device called a strain gauge.
A strain gauge is a sensor whose resistance varies when a force is applied. It converts force into a change in electrical resistance, from which torque can then be measured.
In the case of a crank arm power meter, a strain gauge will measure how much your crank arm is flexing when you push down on the pedals, converting the flex into electrical resistance. Based off the electrical resistance, the power meter electronics can convert this into the amount of torque the rider is generating.
It all comes down to the magic formula:
Power (Watts) = Torque x Velocity (Distance ÷ Time)
When determining the accuracy of a power meter, the number of strain gauges, their alignment and the materials used, all play a major role. The microscopical bending that the strain gauges measure must be precise, in order to determine an accurate amount of torque.
What are the different types of power meters?
Power meters can be placed on a few key locations on a bike. Each type of power meter has advantages and disadvantages which are discussed below.
Crank (Spider)-based power meters are located on the cranks of the bike and measure power using a strain gauge inside the crank spider. They are one of the most common power meters used by professional athletes due to their accuracy, weight, consistency and durability. These cranksets/power meters can be interchanged between bikes (with a little work and also depending on compatibility). Some examples are the Quarq DZero, FSA PowerBox, Power2Max NGeco and SRAM Origin.
Crank arm-based power meters are located on the inside of the crank arm and measure the force on the arm. They tend to be more common, affordable and lighter than other power meter types. These power meters can be single-sided for left leg power only or double-sided which allows you to measure the power of the left and right leg independently. If compatible, crank arms can be relatively easy to swap onto another bike. Some examples are the 4iiii and Stages power meters.
Pedal-based power meters have strain gauges incorporated inside the pedal. They are one of the more popular power meters as they are easy to install, simple to use, can measure left and right leg power independently, can be swapped easily between bikes and are compatible with almost any crankset. They are available as either a single pedal or dual system. The only downside of the pedals is that they are vulnerable to damage because of their location. They can also be useful when swapped onto an indoor or gym bike which is compatible with cycling software such as Zwift. Some examples are the Favero Assioma Duo, Garmin Vector 3, Look Exakt and Quarq PowerTap P2 pedals.
Handlebar-based power meters such as the Velocomp PowerPod have a GoPro attachment which can therefore be easily attached to any compatible bike mount, making it very easy to swap between bikes. These power meters use an accelerometer as well as an elevation, speed and wind pressure sensor, in order to measure a rider’s power output. Although it has an unusual method of calculating power by measuring the wind or ‘opposing forces’ that a rider experiences, through testing it has been proven to be quite accurate. The Velocomp PowerPod is one of the most affordable power meters available. The obvious downside is that it won’t work on indoor trainers.
Bottom bracket-based power meters measure torque in the axle. They aren’t the most popular type of power meter out there as they can be difficult to install and aren’t compatible with all bottom bracket systems, however like crank based power meters, they are very accurate. Another benefit is that the power sensor and electronics are well protected inside the bottom bracket and can provide slightly better weight balance. An example is the Rotor 2INPower as shown below.
Wheel hub-based power meters have strain gauges in the rear hub which measure power. They are quite affordable, reliable and are convenient to swap between bikes. Quarq (PowerTap) is the main manufacturer of wheel hub-based power meters. They offer the power meter as a rear wheel hub (which needs to be custom built/laced) or as a complete wheel/wheelset. One downside is that they do add a little extra weight.
Which power meter should I choose?
There are plenty of great power meters available. Most power meters are generally quite accurate and add a little extra weight, so it all comes down to what you will use the power meter for and how often you will use it, as well as bike compatibility, ease of installation, simplicity of swapping between multiple bikes (if need be) and at the end of the day, the amount that you are willing to spend.
If you are looking to buy a power meter, we have compiled a list of the best and most popular power meters that are available to buy.
View the most frequently asked power meter questions on the Power Meter FAQ page.
