Picked up a 200W panel off Facebook Marketplace for £40 — worth the hassle?

Honestly £40 for a 200W panel is a decent score if it tests out properly. I picked up a couple of second-hand panels for my garden office last year — one was fine, one was putting out about 60% of rated wattage. You just don't know until you check.

Few things I'd do straight away:

• Test open-circuit voltage with a multimeter on a clear day — should be close to the rated Voc on the label
• Check for hotspots or delamination — hold it up to the light or use a thermal camera if you can borrow one
• Look for cracked cells through the glass

The real "hassle" factor for me wasn't the panel itself, it was not knowing the history. No idea how many years it had been on a roof, what orientation, whether it had ever been shaded badly and caused cell damage.

That said, for a static caravan or a small shed setup where you're not depending on it critically, a £40 gamble is pretty reasonable. Worst case you're out £40 and a couple of hours. I've spent more on a dodgy Renogy cable that turned out to be undersized.

What charge controller are you pairing it with? That'll matter more than the panel age in terms of getting the best out of it. Victron SmartSolar will at least give you decent MPPT data so you can see if the panel's underperforming over time.

What were the specs on the label — any idea of the make?

@LisaHunt88 — the classic second-hand panel lottery! I've played this game more times than I care to admit sourcing bits for the shepherd's hut.

Key thing people skip: test it under consistent, direct midday sun with a proper clamp meter, not just "it's charging, must be fine." A panel limping along at 60% capacity will quietly throttle your whole system without screaming about it.

Also worth checking the junction box on the back — peel back that rubber flap and look for signs of moisture ingress or dodgy DIY soldering. I've seen some creative workmanship on marketplace panels that would make a sparky weep.

If it tests well, £40 for a genuine 200W is a proper result. If it tests at 60-odd percent... well, you've essentially bought a £40 panel that's actually a 120W panel. Maths don't lie.

@LisaHunt88 £40 is tempting but I'd want to clamp meter that thing before committing to any serious install. Shading damage and delamination are the killers with used panels — visually they can look mint but the cells underneath are cooked. I picked up three "200W" panels off a local farm clearance a couple of years back for similar money, ran them through my Victron MPPT's history and two were throttled down to about 140W real-world output on a clear day. Still usable in my setup but not what was advertised.

Check the junction box too — dodgy connections there are a genuine fire risk if moisture has gotten in. If you can test Voc and Isc against the datasheet on a clear day around solar noon, that'll tell you a lot. Don't skip that step for the sake of ten minutes.

@LisaHunt88 the 60% output scenario is precisely why I always insist on testing under consistent conditions before buying secondhand. A clamp meter tells you current, yes, but you really want a proper open-circuit voltage and short-circuit current reading against a known irradiance figure — ideally around solar noon on a clear day.

What nobody mentions is that degraded cells often look perfectly fine visually. I picked up three panels for the motorhome last spring, all apparently identical. One had a microfracture across two cells — invisible until I checked the Isc against the others and it was noticeably low.

At £40 the maths can still work out even if it's only performing at 75-80%, but I'd want to know before it's wired into a Victron MPPT and causing mysterious underperformance that takes you weeks to diagnose.

@LisaHunt88 £40 is solid if it checks out. One thing I'd add — worth inspecting the junction box on the back before anything else. Had a panel off a local farm sale that tested okay on the clamp but the J-box cover was cracked and letting moisture in. Caused grief down the line.

Also check the frame corners for stress fractures if it's been moved around a lot. Micro-cracks won't always show on a basic output test but can degrade faster over time, especially through a UK winter.

If it passes visual and gives decent Voc/Isc figures on a clear day, £40's a bargain. Just don't skip the physical inspection.