Anyone else struggling to get decent output from a 200W panel in a Scottish winter?

I've had a Renogy 200W mono panel on my shed roof since September, paired with a Victron SmartSolar 100/20 MPPT controller and a 100Ah AGM battery. During the summer it was brilliant — regularly hitting 10–12A on a clear afternoon. Now we're into December and I'm lucky to see 2–3A even on a "bright" day, and yesterday I got a grand total of 14Wh all day. Starting to wonder if I've made a terrible mistake siting it up here in Perthshire.

I know shorter days and low sun angles are part of it, obviously, but I'm questioning whether I've got the tilt angle right. The panel's fixed at about 30° at the moment. I've read that steeper angles — something like 60–70° — work better in winter to make the most of the low sun, but the shed roof dictates the angle so I can't easily change it. Has anyone added a tilt frame to get around this, or is it just not worth the faff for a fixed installation?

Also curious whether anyone's running a second panel in winter just to compensate for the lack of hours. My loads are pretty modest — LED lighting, a phone charger, and occasionally a 12V pump — but even that feels like it's pushing it some days. Would a second 200W panel wired in parallel actually make a meaningful difference, or am I just throwing money at a fundamentally gloomy problem?

@GlenLover what angle is your panel sitting at? I've read that dropping to a steeper tilt (closer to 60-70°) in winter makes a noticeable difference at northern latitudes — low sun angle means a shallower panel is basically pointing the wrong way.

Also curious what your Victron app is showing for peak input voltage vs your actual wattage. I had a similar issue with my van build and it turned out voltage was fine but current was terrible due to partial shading from a vent I'd forgotten about.

Are you in a valley by any chance? Even a nearby hill cutting off that low winter sun for an extra hour or two each day could be killing your output before you've even started.

What's your typical daily Ah consumption at the moment — worth knowing if it's a generation problem or a storage/sizing one?

FenlandDweller | Posts: 847

@GlenLover Totally feel your pain, though I'm a fair bit further south than you! A couple of things worth checking — what angle is your panel mounted at? For Scottish winters you really want to be pushing towards 60-65 degrees from horizontal to catch that low sun properly. Also, have you cleaned the panel recently? Even light lichen or grime kills output dramatically in low-light conditions.

The other thing I'd flag is your AGM — cold temperatures genuinely reduce usable capacity significantly, sometimes 20-30% below 0°C. Your Victron should have a temperature compensation setting; make sure that's configured correctly or invest in a battery temperature sensor if you haven't already.

Realistically though, a Scottish December is going to give you maybe 1-2 peak sun hours on a good day. Sometimes you just need a backup source. What are you actually running off it?

@GlenLover Completely normal for Scotland in winter, unfortunately. I'm not in Scotland myself but I've had similar frustrations with my boat setup on overcast days — a 200W panel can drop to as little as 10-20W in heavy cloud and low sun angles. A few things worth checking:

• Panel orientation — even a few degrees off south makes a noticeable difference
• Soiling/lichen — winter damp encourages growth on panels surprisingly fast
• Battery condition — AGMs can lose capacity in cold temperatures

Your Victron SmartSolar should give you decent data via the VictronConnect app. Worth pulling the yield history to see whether it's genuinely poor generation or something downstream. If you haven't already, the Bluetooth dongle is worth every penny for diagnosing exactly this sort of thing.

Don't abandon hope — even in Scotland a clear cold day can produce decent results.

@GlenLover Worth mentioning something nobody's touched on yet — low-light performance degrades significantly with partial shading, even minor stuff like frost patches or lichen buildup on the cell surface. I lost nearly 40% output on my static caravan setup one winter before I realised a corner of the panel was barely shaded by an overhang.

Also check your Victron app's historical data carefully. The SmartSolar logs are genuinely useful here — look at whether your yield is dropping due to irradiance alone or whether you're seeing unexpected voltage behaviour suggesting a cell issue or a poorly-performing bypass diode.

A 200W mono should still be pulling something useful even in Scottish December daylight, assuming clean panels and decent orientation. If you're seeing near-zero on clear cold days, I'd suspect a wiring or controller issue before blaming the weather entirely.

MarineVicky | Posts: 312

Living in my motorhome year-round means I've wrestled with exactly this. One thing nobody's mentioned yet — panel angle makes a dramatic difference in winter. The sun barely clears the horizon in Scotland, so if your shed panel is at a shallow fixed tilt, you're practically presenting it edge-on to what little light there is.

I rejigged mine to around 60° for the darker months and squeezed a genuinely surprising improvement out of what felt like a hopeless situation. Obviously a shed isn't as easy to adjust as a motorhome, but even a simple adjustable bracket could transform your numbers.

Also worth checking your Victron app for the "yield today" graph — if you're seeing a tiny bell curve that barely lasts three hours, the angle issue is almost certainly compounding everything @PanelJulie and @FenlandDweller have raised.