May. 12, 2025
In cycling, many things affect how fast you go. Winds, gradients, rider weight, road surface and many other factors determine your speed. This means it can be difficult to gauge your effort based on speed alone. A power meter allows riders to measure their efforts regardless of these factors. They provide an objective measurement of real output. This affords the rider numerous advantages.
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This is why power meters have become essential tools for cyclists of all levels, their coaches as well as sports scientists – who use them as a fundamental way to measure and improve cycling performance. Power meters can unlock more endurance and speed than any other training tool.
Here are just a few of the ways you can use a power meter to improve your performance:
Perhaps the biggest advantage to a power meter is that it removes the guesswork that goes into training and racing. With a power meter, you can quantify exactly how hard you are working (as your effort is measured in watts). Many people use a heart rate monitor in their training. This can be a great training tool in addition to power meters, but training with only heart rate can have limitations. While power can be measured instantly, heart rate is a lagging measurement. This means during training, it takes time for heat rates to rise and fall making it difficult to gauge training, especially during short, fast efforts. Watts are a much more accurate way to measure your effort.
Riders who are new to cycling can often build some base fitness just from spending time on the bike. However, after base fitness is achieved, riders will generally start to see their fitness improvements slow or plateau. A structured training program where you focus on different intensities at varying durations is then needed in order to improve your fitness and power. A power meter can help with this.
Power meters provide highly accurate details about how your fitness is changing throughout the season. You can closely track your average power numbers at given distances, your maximum power numbers, your functional threshold power and more. Using software like TrainingPeaks and their Performance Management Chart, you can track a variety of important metrics. The information gained from this type of software and analysis is very helpful.
Many cyclists who race use power to manage their efforts. When training with a power meter, you will be able to see what easy, manageable and maximum efforts look like. A power meter then allows you to monitor your effort in racing to ensure you are not pushing too hard too early, or starting too easy.
With a power meter, there’s no lying. You get immediate, accurate performance assessment. This can serve as a great motivational tool. There is nothing more satisfying than ending an interval or a ride and seeing an increase in your average or maximum power numbers. A power meter can really help you hit that 100% effort target and can serve as a great training tool because of this alone.
If you have a coach or are thinking about getting one, a power meter greatly improves the value that they can provide. A power meter will provide a wealth of data for your coach. In addition to power, things like speed and cadence are also informative. With this data, the coach can create a plan that is tailored to your needs and by continuing to view data from your rides, they can closely monitor your performance and make adjustments where necessary.
It’s important to understand that selecting and buying a power meter depends on a number of personal factors (your bike, budget, etc.). There is no such thing as ‘the best power meter’. The right power meter for you might not be good for the next person. We never recommend a power meter to a customer until we understand their own unique set of circumstances. For riders that are new to power meters, we recommend focusing on three areas: (1) Compatibility, (2) Features and (3) Price.
Or, you can use our PMC Power Up Tool. This allows you to view power meters based on factors that are most beneficial to you. For example, you can search by price, brand, power meter type, power measurement, compatibility, ease of use and more!
Compatibility simply refers to whether the power meter will fit with your current frame or components. For example, if you’re looking at a crank-based power meter, is it compatible with your frame and bottom bracket? Maybe you’re looking at a power meter pedal. Is it compatible with your shoes and cleats?
If the power meter you are interested in isn’t compatible with your bike or components, it’s time to look at another power meter. (Unless you’re willing to make a change to your components in order to accommodate the power meter.) The last thing you want to do is buy a power meter only to later find out it’s not compatible with your bike. So be sure to confirm compatibility before purchasing. All of our product listings contain a compatibility section – so you can look there for notes on compatibility, or give us a call and we can help.
In general, there are more options for the road then there are for the other cycling disciplines (mountain, track, cyclocross, etc.). However, as more power meters continue to enter the market, the other disciplines are quickly catching up.
There are several features you will probably want to consider when buying a new power meter. We have listed them below in order – starting with the most important. But the order below is just how we look at power meters. Again, we all have our own unique set of considerations. Maybe you have to move a power meter between bikes, in which case transferability will be higher on your list. Alright, let’s check them out.
Accuracy refers to whether the power meter is indeed measuring what it claims to be measuring. For example, if it’s transmitting 225 watts to your head unit, are you actually producing 225 watts, or are you producing 215 watts instead? This must be listed first as it’s usually one of the more immediate things people think about when buying a power meter. However, the truth is, while accuracy is of course key when using any power meter, this is not something most cyclists need to worry much about. All the direct force power meters we carry are tried and true, and are very close to one another in terms of accuracy (+/- 1.5% or better) – assuming it is installed and calibrated correctly.
If absolute accuracy is your goal, there are some super precise power meters that have been certified accurate all the way up to +/- 0.5%. So, if that’s what you’re looking for, more power to you (pun intended). But again, for most cyclists, other features (and of course price), usually prove more important.
Nothing is more frustrating than a piece of faulty equipment. You want your power meter to work and be reliable, every day. Reliability is key when looking at power meters so be sure to do some research in this regard. Fortunately, most of today’s units rank high in terms of reliability. Again, contact us here with questions.
Transferability refers to how easy the power meter is to transfer from one bike to the next. If you have multiple bikes but only one power meter, it’s nice to be able to move the power meter from bike to bike. Some power meters are easy to transfer; others not so much.
Generally, the easiest power meters to transfer are pedal-based power meters. Next easiest are usually crank arm-based power meters. Then there are crank- or spider-based power meters – which can be moved among bikes – but typically aren’t due to the time it would take to do so, as well as potential frame compatibility issues between your bikes.
Installation usually goes hand-in-hand with transferability. Power meters that are easy to transfer are usually easy to install. The easiest power meters to install are pedal and crank arm power meters. Spider or crank power meters on the other hand require more work. However, assuming you’ve purchased a power meter that is compatible with your bike and bottom bracket, even these are relatively straightforward to install and mostly require common tools.
In addition, assuming you’re not moving the power meter from bike to bike frequently, keep in mind that installation is a one-time thing. So even if the installation process is a bit more involved, don’t let this deter you too much if the power meter checks all of your other boxes.
Some power meters offer independent left/right power measurement. With this feature, you can measure how much power each leg is generating independently. While left/right power measurement is a very cool feature, there is some debate as to how meaningful this information is and whether you can, or even should, try to even out any imbalances you might find.
There are two types of left/right power – actual and estimated. Power meters such as ROTOR’s 2INpower SL or pedal-based power meters, measure both legs independently. They combine the data to give you total power. ROTOR does this by locating a power sensor on both crank arms. Whereas the pedals house a power sensor in each pedal.
On the other hand, spider-based power meters such as the Quarq power meter only estimate how much of your total power is coming from each leg. This is because there is only one power meter on the bike (in this case in the spider), so the power meter needs to make some assumptions. Specifically, they take power from your left and right down strokes (where most of your power is produced) in order to determine how much power each leg is producing separately. To be clear, this estimation is only in regards to your left and right power destitution. When it comes to calculating your total power (the important number!), they are very accurate and don’t have to make any estimates as all of your power passes through the spider.
Your power meter will communicate with your bike computer, smartphone or tablet through one of two wireless protocols: ANT+ or Bluetooth SMART. Note that nowadays, most power meters are compatible with both.
ANT+ is a 2.4 GHz wireless network which is used to send standard information wirelessly from one device to another. It allows your power meter to communicate with your head unit. All power meters and head units we sell are compatible with ANT+ technology.
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Bluetooth SMART technology is also a wireless protocol, however it allows you to connect your power meter with smart phones and tablets. It also allows for pairing with popular training apps such as Zwift.
There are two aspects you might want to consider when looking at the battery for your power meter: battery type and battery life.
More and more power meters are coming with rechargeable lithium-ion batteries. Rechargeable batteries offer a bit of a trade-off. On one hand, you never have to worry about replacing the batteries in your power meter. However, rechargeable battery life is typically less than that of a replaceable battery.
The most popular replaceable battery is the CR coin-cell battery. These batteries are cheap and you can find them virtually anywhere. Other batteries that are used are AA (ROTOR INpower V3) or LR44/SR44 (Garmin Rally). We always recommend keeping a few batteries on hand to eliminate the risk of being without a battery when you need one.
Battery life largely depends on the type of battery your power meter has. As mentioned previously, rechargeable batteries have a bit of shorter life. On average, power meters with rechargeable batteries typically get around 150 hours of battery life. However again, this is an average and some, such as the 4iiii PRECISION 3P+ get as much as 800 hours!
This compares to power meters with replaceable batteries which get closer to 250 hours on average. But again, the range is wide for this group as well as the ROTOR INpower V3 gets 300 hours while the Garmin Rally gets closer to 120 hours.
All power meters add weight, some more than others. Power meters such as a left-side only crank arm-based power meter might only add 10-20 grams to your bike, while others might add closer to 200-250 grams or more (but this all depends on the component you are replacing). When factoring in the weight, remember to focus on added weight by taking into account the component you’re replacing. For example, if the crank-based power meter you’re considering weighs 700 grams, and your current crank weighs 500 grams, the net addition is 200 grams.
While it’s important to pay attention to how much weight is added and where, it’s not worth fussing over. The benefits of training with power will more than offset any weight gain. If you’re a weight weenie (and we don’t say this is a bad way), weight might move up on your list. Otherwise, we think it’s safe to keep it here.
Power meters start at around $220 and can reach $2,500 or more. Some of the more expensive power meters offer features like carbon fiber cranks, independent left/right power measurement and high levels of accuracy and consistency. However, this isn’t to say that a lower priced power meter can’t do the job. In fact, nothing could be further from the truth. The vast majority of power meters are very capable assuming you have them set up properly and calibrated – so don’t assume that more expensive is necessarily better. If you find a power meter that meets your criteria and is in your price range – than it’s likely a winner for you.
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Don’t worry, you won’t need your high school physics text book for this part. We just want to point out another characteristic that can be used to tell a high-quality PSU from a bad one. Once you know the basics, you’re a lot less likely to make a bad purchasing decision. So, let’s dive right in.
Idle Current And Idle Power
One problem that plays an especially big role in the case of switching power supplies is the so-called idle current, which results from inductivity. Note that idle current has nothing to do with the idle state of your computer. This idle current only transports energy between a generator and a load, but doesn’t end up benefiting the load in any way. Again, load in this context has nothing to do with a PC at full throttle, but refers to a component that uses power. Think of it as a power shuttle that isn’t involved beyond its role as a transporter. This idle current has to be reduced as much as possible and as early as possible, since it causes power loss in conjunction with ohmic resistors, manifesting as heat. This idle power consumption is a waste, and should be kept as low as possible through appropriate circuitry.
Effective Power And Apparent Power
Unlike idle power consumption, effective power measures the power that is actually used, while apparent power refers the sum total of the effective power and the cumulative idle power.
Power Factor
This factor is the result of the ratio between effective power and apparent power, falling somewhere between 0 (worst) and 1 (ideal). Thus, the higher the power factor the less energy goes wasted back to the mains network. Although residential consumers do not have to pay for apparent power, in order to minimize apparent power usage, the EU standard EN-3-2 states that all switched mode power supplies with output power of more than 75W must include a passive PFC converter. In addition, 80 PLUS certification requires a power factor of 0.9 or more. Some years ago, many PSU manufacturers used passive PFC in their products. PPFC uses a filter that passes current only at line frequency, 50 or 60Hz, so the harmonic current is reduced and the nonlinear load is transformed to a linear load. Then, with the usage of capacitors or inductors, the power factor can be brought close to unity. The disadvantage of PPFC is that it attains smaller power factors than APFC and requires a voltage doubler for the PSU to be compatible with 115/230V. On the contrary, PPFC has higher efficiency than APFC, something that probably most of you didn’t know. But that doesn't mean PPFC-equipped PSUs are more efficient than APFC ones, since PPFC units are often based on older designs that cannot compete with the performance of modern APFC PSUs.
Practical Application
Swipe to scroll horizontallyActive PFCAs the name implies, active power factor correction (APFC) employs a circuit that actively corrects the power factor. As we just explained, the power factor is an important parameter in the world of PSUs, since it describes the ratio between effective power and apparent power:Pros:• An almost ideal power factor close to unity• Very stable current output even under input voltage variations• Demands for smaller parts (transformer) Cons:• Higher initial cost• More susceptible to faults• Energy losses occur onto the APFC’s boost diode (and the FETs)
Swipe to scroll horizontallyPassive PFCPassive PFC attempts to reduce idle currents by using large choke coils. While this method is simpler and cheaper, it is also much less effective.Pros:• Cheaper (depending on the power handling range) • Practically no electro-magnetic interference• More efficient than APFC (beware: this doesn’t mean though that PPFC PSUs are more efficient that APFC ones)Cons:• No automatic universal voltage input• Not suitable for higher power levels • Heavier due to the larger PFC choke • Lower power factor ranging from 70% to 80%Power supplies with passive PFC should be considered outdated and can be considered inferior. And don't confuse efficiency and PFC!
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