The power meter is the single most useful thing you can put on a bicycle. Not the most exciting. Not the flashiest. But if you want to train with any real precision, to know whether you are actually getting fitter or just feeling like it, there is no substitute. Heart rate tells you how your body is responding. Power tells you what your body is actually doing. One of those is a fact. The other is a feeling.
I had Uli Schoberer on the podcast — the man who invented the modern cycling power meter with SRM back in 1986. What struck me most was how simple the original idea was. Strain gauges on the crank spider, measuring the tiny flex in the metal as you push. That basic principle has not changed in forty years. What has changed is where those strain gauges sit, how much the whole thing costs, and how many options there are to confuse you.
The buying guides you find online are usually written by people trying to sell you something. This one isn't.
The Three Types That Actually Matter
There are three places you can measure power on a bicycle: the crank (either the spider or the arm), the pedals, or the rear hub. Each has trade-offs. None of them is perfect.
Crank spider-based. This is the original. Strain gauges sit in the spider — the piece that connects your crank arms to the chainrings. SRM still makes these. Quarq (owned by SRAM) makes them. Shimano now builds them directly into their Dura-Ace and Ultegra cranksets. They measure total power directly, both legs combined, and they are the most accurate type available — typically plus or minus one percent. The downside is cost and compatibility. A spider meter ties you to a specific crankset, a specific bottom bracket standard, and often a specific groupset generation. Swapping one between bikes is a full crankset swap.
Crank arm-based. Stages and 4iiii took a different approach. Instead of the spider, they bond strain gauges to the left crank arm (or both arms for dual-sided versions). This made power meters dramatically cheaper — a single-sided Stages or 4iiii can be had for around 300 euros. The catch is that single-sided units only measure your left leg and double it. If your legs produce equal power, the number is accurate. If they do not — and they usually do not — you get an estimate that can be off by three to five percent from your true total. Dual-sided versions from both brands fix this but cost more.
Pedal-based. Garmin Rally (the successor to Vector), Favero Assioma, and a handful of others put the strain gauges inside the pedal spindle or body. This is where it gets really interesting for most riders, because pedals are the one component you can move between bikes in five minutes with a single wrench. The Favero Assioma Duo has become something of a default recommendation for good reason — it measures both legs independently, it is accurate to about plus or minus one percent, and it costs significantly less than most spider-based meters. The Garmin Rally offers Look Keo, SPD-SL, and SPD cleat options, which is useful if you run mountain bike pedals on a gravel bike.
Hub-based. PowerTap built their business here. A strain gauge in the rear hub shell measures the torque going into the wheel. The concept is sound and the accuracy was decent, but hub-based meters have one fatal flaw: they tie your power data to a single wheel. You cannot swap wheels for race day without losing your power data. PowerTap effectively exited the market, and no major manufacturer has stepped in to replace them. If you find a secondhand PowerTap hub, it still works and makes a fine dedicated indoor training wheel. But as a new purchase in 2026, it is not a serious option.
Accuracy vs Consistency — What Nobody Tells You
Every brand leads with accuracy claims. Plus or minus one percent. Plus or minus one and a half percent. Plus or minus two percent. Most buyers fixate on this number and assume the lower one is always better. It is not always better, and let me be really clear about this — for the way most of us actually use power data, consistency matters far more than absolute accuracy.
Here is why. If your power meter reads three percent high on every single ride, your FTP test will read three percent high too. Your training zones, derived from that FTP, will be three percent high. Your intervals, set by those zones, will still be at the correct actual intensity. Everything stays internally consistent. You will train effectively. Your fitness will improve. The number on the screen will just be slightly wrong compared to someone else's number — and comparing your watts to another rider's watts is meaningless anyway unless you are on the exact same meter.
Where accuracy starts to matter is when you switch meters. If you test your FTP on a Stages single-sided unit and then race with a Quarq spider meter, those numbers will not match. Your pacing strategy, built on the Stages FTP, will be wrong on race day. This catches people out constantly. The fix is simple: test and race on the same meter, or if you cannot, test on both and know the offset between them.
Single-Sided vs Dual-Sided — The Real Difference
The single-sided question is the biggest decision most buyers face, because it is where the biggest price jump sits.
A single-sided meter measures your left leg and multiplies by two. The assumption is that you produce 50% of your power with each leg. Most riders do not. Studies show the typical split is somewhere between 48/52 and 46/54, and some riders — particularly those with old injuries, leg length discrepancies, or years of muscle imbalance — can be more uneven than that.
If your split is 48/52, a single-sided meter reading your left leg will show a total power about four percent lower than your actual output. That is not a disaster. It is consistent, so your training still works. But it means your FTP number is about four percent lower than reality, and if you are pacing a time trial or a long climb by that number, you are leaving watts on the table.
If your split is 45/55 — which is not uncommon in riders recovering from knee injuries or with significant bike fit issues — the error jumps to ten percent. That is meaningful.
The good news is that if budget is tight, a single-sided meter is still vastly better than no meter at all. You can always upgrade later once you know power training is something you will stick with.
The Brand Breakdown — What I Would Actually Buy
Here's what I would honestly recommend at each price point, no affiliate angle, just what I have seen work.
Budget entry (300-400 euros): Stages Gen 3 or 4iiii Precision. Both are single-sided, left crank arm units. Both are accurate to about plus or minus one and a half percent. Stages has been around longer and has slightly wider crankset compatibility. 4iiii is marginally thinner and lighter. Either one gets you into power training for the cost of a pair of decent tyres. Check that the model matches your crankset — Shimano 105, Ultegra, Dura-Ace, and SRAM Rival, Force, and Red are all available, but you need the right generation.
Best value (500-650 euros): Favero Assioma Duo. This is the recommendation I make most often. Dual-sided, pedal-based, plus or minus one percent accuracy, and you can move them between bikes in minutes. They use a Look Keo-compatible cleat, so if you already ride Look or Keo, the transition is painless. Battery is rechargeable via USB, which means no hunting for coin cell batteries mid-season. The only downside is that they do not work with SPD or SPD-SL cleats, though Favero released the Assioma Pro MX for SPD compatibility.
Premium all-in-one (700-1200+ euros): Shimano Dura-Ace or Ultegra power meter crankset, Quarq DZero, or SRAM AXS power meter spider. If you are already running Shimano or SRAM and want the cleanest integration, these are the answer. Shimano's R9200-P and R8100-P cranksets put the strain gauges in the crank arms with dual-sided measurement and report directly to any ANT+ or Bluetooth head unit. Quarq has decades of reliability behind it and is the default in the SRAM groupset family. SRM is still the gold standard for accuracy and has been the choice of WorldTour teams for thirty years, but the price reflects that — you are paying for lab-grade precision.
If you need SPD cleats: Garmin Rally XC or Favero Assioma Pro MX. The Garmin Rally system lets you swap pedal bodies between road (Rally RS with Look Keo), road (Rally RK with Shimano SPD-SL), and off-road (Rally XC with SPD). The sensing pods stay the same. It is clever engineering and worth the premium if you ride both road and gravel or MTB. The Favero Assioma Pro MX offers dual-sided SPD measurement at a lower price point than the Rally XC.
Temperature Drift and Zero-Offset — The Five-Second Habit That Saves Your Data
Here is where it gets really interesting from a practical standpoint. Every strain-gauge power meter is affected by temperature. The strain gauges are bonded to metal. Metal expands and contracts with heat and cold. When the temperature changes, the baseline reading of the strain gauge shifts — this is temperature drift.
What this means in practice: if your bike has been sitting in a car boot on a hot day, or in a cold garage overnight, and you start riding without calibrating, your power numbers for the first twenty to thirty minutes can be off by five to ten watts or more. Modern meters compensate for this automatically to varying degrees, but none of them are perfect.
The fix takes ten seconds. Before every ride, do a zero-offset through your head unit. Garmin, Wahoo, Hammerhead — they all have the option in the sensor settings. Clip in, sit still, press calibrate. Done. This resets the baseline and removes any temperature drift. I do it every single ride. It is the cheapest way to keep your data clean.
What Most People Get Wrong
The most common mistake I see is riders buying a power meter and then not actually changing the way they train. A power meter is not a speedometer for watts. It is a training tool, and it only works if you use it to structure your riding — test your FTP, set your zones, design your sessions around specific power targets, and track changes over time.
The second most common mistake is meter shopping based on accuracy specs alone. A plus or minus one percent meter that you leave in the box because pedal swaps annoy you is worth nothing. A plus or minus two percent meter that lives on your bike and records every ride is worth everything.
Buy the one that fits your bike, your cleats, your budget, and your willingness to actually use it. Then ride it for a year before you decide whether you need something fancier.
Where to Start If You Are Still Unsure
If you have never trained with power, start with a single-sided Stages or 4iiii. Spend three months learning what your numbers mean — what Zone 2 feels like, what your FTP actually is, how power changes with fatigue and heat and fuelling. If after three months you find yourself wanting left/right balance data or better accuracy, sell the single-sided unit and move to the Favero Assioma Duo. You will have lost very little money and gained the knowledge to actually use the upgrade.
If you want to go deeper into power-based training and connect with other riders figuring this out, the Roadman Cycling community on Skool is where a lot of these conversations happen — real riders sharing real data, no gatekeeping.
The power meter changed cycling more than any other piece of technology since the derailleur. Uli Schoberer built the first one in a university lab nearly forty years ago. Today you can get one for the price of a weekend away. There is no good reason not to.