This article helps you decide whether you should buy a single or dual-sided power meter.
I have experience with both power meter types, and I discussed this topic with many cyclists, including pros.
Single-sided power meters are more affordable, but they only estimate total power, which will most likely be inaccurate. So…
Should you buy a single or dual-sided power meter?
Buy a single-sided power meter if you are a beginner, have a tight budget, or need a power meter just to pace yourself during long rides or on climbs. Dual-sided power meters are suitable for serious riders who want accurate data and learn more about their pedaling technique.
Continue reading to learn more details.
What Is the Difference Between Single and Dual-sided Power Meters?
The main difference between a single-sided and dual-sided power meter is that a single-sided power meter measures only the power output of one of your legs (mostly left) and then multiplies it by two to get your total power output.
Dual-sided power meters can either measure the power independently on each leg or estimate it using software algorithms.
TIP: You might also be interested in this technical explanation of how cycling power meters work.
Many riders don’t have balanced leg power output (50:50), so using a single-sided power meter may lead to wrong conclusions (more on this topic below).
But, some power meter apps allow you to change the measuring balance to make your estimated power output closer to the real one. However, you must first know what L/R disbalance you have to put in the correct numbers.
Single vs. Dual-sided Power Meters: Pros & Cons
The following table summarizes the pros and cons of single and dual-sided power meters.
| Power Meter Type | Pros | Cons |
|---|---|---|
| Single-sided | • More affordable • Usually easier to install (does not apply to pedal power meters, their installation difficulty is the same) | • Can't provide you with advanced metrics like Left/Right leg balance, power smoothness, etc. • Are subject to power inaccuracies due to L/R leg imbalance |
| Dual-sided | • Can provide you with advanced metrics like Left/Right leg balance, power smoothness, etc. • Are not subject to power inaccuracies due to L/R leg imbalance | • More expensive • Usually more difficult to install (doesn't apply to pedal power meters) |
The most significant disadvantage of single-sided power meters is that they can’t measure the overall power output. Instead, they can only estimate it based on one of your legs (mostly the left one).
Here are the two most common scenarios:
- The power meter will overestimate your overall power if you have 52:48 left/right disbalance (your left leg is stronger).
In other words, if it measures you push 100W with your left leg, the power doubles this value and estimates your overall power to be 200W. However, your real power will be closer to ~192W. - The power meter will underestimate your overall power if you have 48:52 left/right disbalance (your left leg is weaker).
In other words, if you push 100W with your left leg, the power doubles this value and estimates your overall power to be 192W. However, your real power will be closer to ~208W.
So, is this an issue?
Not necessarily because many people forget power consistency ≠ power accuracy.
If you use the same power meter, you will have the same ‘baseline.’ Realistically, your power output may not be accurate, but it will be consistent.
This means you will be able to train based on inaccurate but consistent data and see your progress. However, you will probably note a difference once you switch to a dual-sided power meter.
This is exactly what happened to me. I have done my first FTP test with a single-sided power meter.
My watts were surprisingly low when I did the future tests with a dual-sided power meter. Then I realized that I have an L/R disbalance that caused this discrepancy.
Single vs. Dual-sided Power Meters FAQ
Summary
I recommend single-sided power meters to beginners or riders who just want to pace themselves on longer rides or climbs. If you use the same, consistent, single-sided power meter, you will see your progress over time (although it will most likely differ from your real power).
More serious riders should consider a dual-sided power meter to ensure the long-term consistency and the accuracy of their results.
In addition, dual-sided power meters can measure advanced metrics like left/right leg balance, power smoothness, power phase, etc., that you can leverage in improving your pedaling technique.
You might want to check your maths…
If you have a 48/52-left-right power balance, and you push 100 W left, then a single power meter would show 200 W, instead of the actual ~208 W …
Hi Pascal,
Thank you for pointing this out. It should be ok now. 🙂
– Petr