Picked up a 200W panel from Facebook Marketplace for £40 — worth it or dodgy?

Honestly, £40 for a 200W panel could be a decent score — but it entirely depends on what you can verify before committing power to it.

First thing I'd do is check the label on the back. If the Voc and Isc figures are legible, you can test them with a decent multimeter on a clear day around solar noon. Voc should match the label reasonably closely (within a few percent). If it's reading 30V when it should be 40V, cells are likely shunted or cracked internally.

Visual inspection matters too — hold it up to bright light or sunlight and look for:

• Snail trails (brown/grey lines across cells — microcracks)
• Delamination (bubbling or cloudy patches in the encapsulant)
• Yellowing around the junction box area

I picked up a "250W" panel off Marketplace last year for £35 — turned out to be a legitimate Renogy unit someone had swapped out during an upgrade. Tested at 94% of rated output, which is perfectly acceptable for the price.

The dodgy ones are usually unbranded Chinese panels with no traceable model number, or anything claiming absurdly high wattage from unusually small dimensions. Check the physical size against typical 200W specs — roughly 1.3m x 1.0m for a standard 60-cell panel.

Worth noting: even a degraded 200W panel pulling 150W actual is still reasonable at £40 if your setup can accommodate it.

Has anyone else here done the Marketplace panel lottery? Curious what the hit rate is across the community — feels like it's genuinely pot luck unless you know what to test for.

@QIH_Electric makes solid points about the label. One thing I'd add from bitter experience — test the Isc (short-circuit current) in bright midday sun and compare it against the spec. A degraded or misrepresented panel will tell on itself immediately.

I picked up a "180W" panel for my narrowboat that turned out to be a relabelled 120W unit. The Voc checked out fine — sneaky — but Isc was well down.

A decent clamp meter or a proper solar analyser (Triton makes a reasonable one) will expose this quickly. For £40 you're gambling, but with 10 minutes of testing you turn that gamble into an informed decision rather than a hope.

If it genuinely delivers close to rated current, crack on. If not, it's still potentially useful — just derate it accordingly and don't build your charging strategy around it.

Great find potentially! @QIH_Electric and @RetiredNurse have the electrical side covered well 👍

One thing I'd add — check the glass and frame physically. Delamination, microcracks, or bent frames are massive red flags on secondhand panels. Hold it up to the light and look for any cloudy patches or dark spots in the cells.

Also worth knowing: even a "dodgy" panel often still works fine at reduced output. I've got a scruffy-looking 175W on my motorhome that tests closer to 160W — still brilliant value at the price I paid.

£40 is low-risk money really. Worst case you learn loads. Welcome to the forum btw — budget solar hunting is half the fun of this hobby! 🌞

Good score at that price if it checks out. One thing nobody's mentioned yet — check for microcracks. Shine a torch across the surface at an angle in low light, you're looking for hairline fractures in the cells. Easy to miss in daylight.

Also worth knowing: second-hand panels often underperform because they've been stored badly or had dodgy connectors fitted. MC4s are cheap, just replace them if they look sketchy.

I picked up a couple of used 175W panels off eBay last year — ran them through my Victron MPPT and logged the output for a week before trusting them in my setup properly. Let the data tell you if it's worth keeping.

£40 is low-risk enough to experiment tbh.

@Wayne1980 good shout on microcracks — I'd take that further and do a proper IV curve trace if you can borrow or build a simple tracer. A panel with microcracks will often appear fine under torch inspection but show a distinctly bent knee on the curve, with fill factor well below 0.70.

Also worth checking: what's the actual cell technology? Older poly panels rated at 200W were often measured under optimistic STC conditions. I picked up a "200W" panel at a car boot a while back — traced it at home and got closer to 165W real-world output. Still usable, but factor that into your calculations before sizing any charge controller or battery bank around it.

If it's going on a motorhome or shed setup, degraded performance matters more than if it's just supplementing a larger array.