January 27, 2026 · 3 min read

A Used Power Meter — What to Check Before You Click "Buy Now"

A used power meter can cost half the price of a new one — the fastest route to sensible watt measurement on a limited budget. But unlike a saddle or handlebars, here you're buying electronics with a strain-gauge sensor, and it's easy to overpay or end up with a faulty unit. Here's what to check before you click "Buy Now".

1. Compatibility with your bike

The most common mistake: a great deal that doesn't fit. Before anything else — check the bottom bracket type, crank length, mounting standard and gearing. Crank- and spider-based power meters are tightly tied to a specific standard; pedals are the most universal in this respect, but need matching cleats.

2. Whether the model is still supported

A power meter with no firmware updates and no manufacturer support is a risk: if the app's protocol changes or you hit a pairing problem, you're on your own. Check whether the manufacturer is still releasing updates and whether the model was discontinued years ago.

3. Battery and seal condition

• Replaceable battery (CR2032) — easy and cheap to swap, but check the condition of the contact and the o-ring.
• Built-in, rechargeable battery — loses capacity after a few years, and replacement is often not worth it.
• Traces of moisture or corrosion near the cover — the most common cause of death in a used power meter. Ask the seller for a photo of the inside of the battery compartment.

4. A zero-offset test before you buy

Ask the seller to run a calibration (zero offset) and send a photo of the result. The value should fall within the range stated by the manufacturer and be repeatable across attempts. A big spread between readings is a sign of a damaged strain gauge.

5. Ask for a file from a real ride

The best proof a power meter works — a .FIT file from the seller's last ride. Check it for gaps in the power data, sudden drops to zero at a constant cadence, or absurd peak values. The same things you'd check after your own workout — we covered how to read a file like that in our article on 5 numbers to check after downloading a .FIT file.

6. Single-sided or dual-sided

A single-sided power meter doubles the power measured on one leg. If you have a noticeable asymmetry, the result will be systematically over- or under-stated. For tracking your own progress over time this isn't a problem (the error is constant), but for comparisons with others it is.

7. Remember the difference between measurement sources

A new power meter will almost certainly show different values than your current trainer — and that's normal. Before you conclude you've "lost form", check where the differences between trainer and pedal power measurement come from.

Red flags

• No photos of the serial number, or refusal to provide one.
• "Never tested it, it's been sitting in a drawer" for battery-powered electronics.
• A price well below market for a supposedly working unit.
• No way to pair it with a phone at pickup.

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