Picked up a secondhand 200W panel off Facebook Marketplace — worth it or a gamble?

Done exactly this a couple of times for the van build — mixed results if I'm honest.

First one was a genuine bargain, older Kyocera panel that tested within 5% of rated output even after years on someone's shed roof. Paid £40, still running fine.

Second one was more of a lesson. Looked immaculate but had microcracks you couldn't see without a proper EL test. Output was all over the place depending on angle and cloud cover — classic microcrack behaviour. Ended up binning it after a few months of chasing inconsistent charging.

Things I'd check before handing over cash:

• Test Voc and Isc with a multimeter before you load it in the car — seller should expect this
• Look for delamination around the edges and any yellowing of the encapsulant
• Check the junction box for water ingress or dodgy DIY wiring
• If they can't tell you the make/model, walk away — you want to look up the spec sheet

The Facebook Marketplace solar game is basically pot luck without an EL tester, and nobody's hiring one out for a £60 panel purchase. That said, the savings can absolutely be worth the gamble if you go in with eyes open and don't rely on it as your only source.

What did you end up paying, and do you know the manufacturer? Might be able to help narrow down whether it's likely to be decent quality or not. There's a massive difference between pulling an old Sharp or Kyocera off a roof versus some unbranded thing from a clearance warehouse.

Del72 | 847 posts

@RussGreen that Kyocera find sounds like a result — those old panels were built like tanks. The Japanese manufacturers from that era weren't cutting corners.

My tip for anyone buying secondhand: always ask for photos of the junction box before you commit. That's usually where neglect shows first — cracked seals, corrosion, dodgy DIY wiring jobs. A panel might test fine on a sunny day but water ingress in that box will cause grief down the road.

Also worth checking the frame corners for stress cracks if it's been roof-mounted. Some sellers don't realise they've got damage from overtightened brackets.

For 200W at the right price? Absolutely worth the gamble in my opinion, just go in with your eyes open and ideally a multimeter in your pocket before handing over any cash.

George1972 | 203 posts

@RussGreen what test equipment are you using to check output? That's the bit I'm always uncertain about with secondhand panels — I've got a basic multimeter but I'm not sure that gives me the full picture, especially under real-world conditions versus lab-rated specs.

Also curious whether there's anything obvious to check physically before buying — delamination, micro-cracks, that sort of thing? I've seen panels on Facebook Marketplace locally that look immaculate in the photos but who knows what they're like in person.

Tempted by a couple of 200W Renogy panels listed near me but the seller can't tell me much about their history. Is there a rough age beyond which it's probably not worth the risk regardless of how they test?

RetiredNurse43 | 412 posts

@George1972 Good question — I'd add that even without fancy kit, a basic multimeter will tell you a lot. Check open-circuit voltage (Voc) on a clear day around solar noon, then compare against the panel's label. Should be close to rated figure. For current you really want a clamp meter ideally.

@RussGreen I've had similar mixed luck on Marketplace. My tip is always ask the seller why they're selling — a surprising number will admit if there's been shading damage or a cracked cell underneath the glass. Also worth running your hand across the surface feeling for delamination bubbles. Learned that the hard way with one that looked pristine but had moisture ingress round the edges. Lasted less than a season before output dropped noticeably.

Patience pays off though — the good ones are definitely out there.

Spud79 | 1,134 posts

@George1972 Worth getting a proper clamp meter if you're buying secondhand panels regularly — measures current without breaking the circuit. Combined with a multimeter for Voc you can get a reasonable picture on a clear day around solar noon.

One thing nobody's mentioned: check the junction box carefully. Delamination and cracked glass get most of the attention but a corroded or poorly-resealed J-box is a common failure point on older panels, especially anything that's been roof-mounted in the UK for a few winters. Had one on the narrowboat that looked fine visually but the diodes had failed inside — cost me efficiency for months before I traced it.

For a 200W panel the maths are pretty simple. If it tests significantly below 170W in good conditions, walk away unless the price reflects it.