Power Meter vs. Heart Rate: Which is Better For Training?

Power Meter vs. Heart Rate Monitor: A road bike with power2max power meter on the left side and a top-less man with the Wahoo TICKR heart rate monitor

This article explains whether you should train with power data, a heart rate monitor, or both at once to improve your performance effectively.

I asked myself the same question before I invested in these devices. After reading dozens of articles, having discussions with pro cyclists, and doing some training, I summarized everything I learned in this article.

The difference between a power meter and a heart rate monitor is that the power meter will provide you with objective, instantaneous data of your effort. Heart rate monitors measure heart rate, a lagging indicator of our body’s response to a given effort and can be influenced by other factors like your fatigue. So, the best practice is to use them both at once.

Let me explain why below.

Power Meter Data: Instant and Objective

Power meters provide real-time, objective, and accurate data that eliminate guesswork.

Take a look at the following snapshot from my structured workout.

A snapshot of a part of my structured training in TrainerRoad showing my power and heart rate
This picture shows how my heart rate (red line) reacts to my power output (yellow line)

You can see that the power data (yellow line) are instantaneous, while heart rate, e.g., my body’s response (red line), changes with a delay. The implication is that interval training based on your HR is limiting and inaccurate.

Today’s power meters have an accuracy between ±1% and ±3% (source), which is sufficient for most riders, including pros.

Power meter consistency is no less important, though. It means that the power meter provides you with the same, consistent data in various conditions (altitude, temperature, etc.).

The following table shows the power deviations of multiple accuracy rates and power outputs.

Accuracy Rate / Power Output250W500W1000W
0.5%248.8-251.3497.5-502.5502.5-1005
1%247.5-252.5495-505990-1010
1.5%246.3-253.8492.5-507.5985-1015
2%245-255490-510980-1020
2.5%243.8-256.3487.5-512.5975-1025
3%242.5-257.5485-515970-1030
Power meter accuracy for specific accuracy rate (0.5%, 1%...) and power output (250W, 500W, 1000W)

Power meters are also better than HR monitors for tracking your long-term progress and can show you advanced metrics like your left/right leg balance.

On the other hand, they are more expensive, and their data are more difficult to interpret so you may need a consultation with an experienced trainer.

Are you still not sure if power meters are worth it? Then, check out more reasons to use a power meter.


Heart Rate: Delayed and Subjective

Heart rate monitors are affordable, easy to use, and their data are easy to interpret.

The problem with heart rate is that it just shows your body’s response to a given effort. It is delayed and doesn’t tell you precisely what work (power) you are doing.

Heart rate also varies based on multiple factors such as:

  • Fatigue
  • Age
  • Diet
  • Outside temperature
  • Stress
  • and more

That’s why the HR data are subjective. So, does this mean they are useless?

Not quite.

However, cyclists shifted from ‘training by heart rate’ to ‘training by power with heart rate.’

This is because HR provides you with info about your body and complements the power data, so you (or your coach) can make more educated decisions.

Check out the summary of the pros & cons of power meters and HR monitors.

DeviceProsCons
Power Meters• Measure your efforts instantaneously (without lag)
• Objective (not influenced by external factors)
• Better for tracking your long-term progress
• More expensive models can show leg imbalances
• More expensive
• More difficult to understand and interpret the data
• Some power meters need regular calibration
HR Monitors• Less expensive
• Easy to use
• Easy to understand the data
• HR lag
• HR may be affected by external factors like fatigue, air temperature, sleep quality, etc.
• HR straps may be uncomfortable
The pros & cons of power meters vs. heart rate monitors compared
Sources: roadcyclinguk.com, bikeradar.com, trainerroad.com

I also recommend watching the following video by Dylan Johnson. It includes much well-researched information.


Power Meter vs. Heart Rate FAQ


Conclusion

If you are serious about your training and want to take it to the next level, invest in both devices.

A power meter will provide you with real-time, accurate data you can rely on (browse the best power meters on the market from budget ones to premium).

A heart rate monitor will provide you with information on how your body reacts to a given effort. In addition, it is more affordable so that it won’t ruin your budget.

Remember, though, the most important thing is to interpret the data you get from these devices correctly. It can be a little bit overwhelming for beginners, so I recommend consulting them with a professional coach.

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