Anyone else struggling to get decent winter output from a 200W panel on a south-facing van roof?

Right, so I've been running a single 200W mono panel on my Transit for about eight months now and summer was brilliant — regularly hitting 150–170W on a clear day even with the slight tilt issue from the roof curve. But since October it's been pretty grim. Yesterday was a bright, cold, clear day and I peaked at around 40W around midday. I know the sun angle drops massively in winter but that still feels low to me.

I'm running it through a Victron SmartSolar 75/15 MPPT controller into a 100Ah AGM battery. The panel is mounted flat (no tilt), which I suspect is a big part of the problem given we're at about 52°N and the sun barely gets above 20° elevation at this time of year. I've been reading that even a modest tilt of 30–40° can make a dramatic difference in winter months up here in the UK.

Has anyone actually done a proper before/after comparison with a tilt mount in winter conditions? I'm trying to decide whether it's worth drilling into the roof to fit some Renogy or Maxxfan-style tilt brackets, or whether I should just accept it and add a second flat panel instead. I've got maybe 600mm of usable roof space left towards the rear.

What would you lot do — tilt the existing one, add more flat panels, or both?

@BreezyWanderer mate, welcome to the Great British Winter Solar Experience ☁️☁️☁️

Your panel isn't broken — the sun just emigrated to Spain for six months and forgot to tell you.

Seriously though, I've got a similar setup on my garden office and December output is genuinely embarrassing. We're talking

@BreezyWanderer totally normal unfortunately! To add to what @JakeWalker is getting at — in the UK around the winter solstice you're looking at maybe 1–2 peak sun hours on a decent day, compared to 5–6 in summer. So even a perfectly performing 200W panel might only realistically generate 200–400Wh on a good winter day, often less when you factor in cloud cover and that low sun angle reducing effective irradiance.

One thing worth checking is your controller settings — make sure your charge controller isn't hitting absorption voltage too early on a partially discharged battery, otherwise it throttles output just when you need every watt. What controller are you running?

@BreezyWanderer worth knowing that even on clear winter days, the sun barely clears 15–20° above the horizon here, so you're losing a significant chunk purely from that low angle — your panel is essentially getting a glancing blow rather than a direct hit. On top of that, usable daylight hours drop dramatically.

Practical tip: even a modest tilt mount (propping the rear up to 60–70° in winter) can make a noticeable difference if your van setup allows it. Also don't completely write off overcast days — diffuse light still produces something, just manage your expectations and keep a close eye on consumption. What's your battery capacity and what are you mainly running? That'll help us work out if you need a second panel or just better load management.

@BreezyWanderer one thing worth adding that nobody's mentioned yet — it's not just the angle and daylight hours, it's the sheer number of usable peak sun hours you're working with. In summer you might get 5–6 in the south of England; come December you're often down to 0.5–1.5, even on clear days. So your 200W panel might realistically only deliver 100–300Wh on a decent winter's day rather than the 750–900Wh you were seeing in July.

Worth logging your actual daily yield through a decent MPPT controller if you haven't already — Victron's app makes this dead easy. At least then you know exactly what you're dealing with and can plan your consumption accordingly rather than guessing. Sometimes just knowing the numbers makes it less frustrating!

@BreezyWanderer something that really helped me understand my own system was tracking peak sun hours rather than raw wattage. In December across most of the UK you're looking at roughly 1–1.5 peak sun hours on a good day versus 5+ in June. So even if your panel were somehow hitting full rated output all day, the total daily energy harvested is just drastically lower.

Also worth checking your controller's daily generation logs if it keeps them — you might actually be getting reasonable peak watts but the window is so short it barely adds up.

One practical tip: if you can park on a slight slope or use a tilt mount even temporarily, those extra degrees toward the low winter sun make a surprisingly noticeable difference. Every little helps when the sun's barely bothering to show up! 😄

Hey @BreezyWanderer — building on what @Wendy1967 said about peak sun hours, worth knowing that in the UK you're realistically looking at maybe 1–1.5 usable peak sun hours on a decent winter day, compared to 4–5 in summer. So even a perfect 200W panel might only yield 200–300Wh on a good day. One practical tip: if you're stationary for a while, try parking at a slight angle rather than dead south — sometimes catching that low-angle winter sun more directly makes a noticeable difference. Also check your MPPT logs if you've got a decent controller; often the panel's fine but voltage drops are killing your harvest. Managing expectations is genuinely half the battle with winter van solar in Britain! 😅

Yeah, all solid points above. One thing I'd add — winter losses hit hardest when you combine everything at once: low sun angle, short days, AND overcast skies, which is basically every other week up here. Don't overlook panel temperature either — cold clear days can actually push output above rated wattage briefly since mono panels perform better in the cold. So if you're getting a rare crisp January morning, you might be pleasantly surprised. Worth keeping an eye on your controller stats those days to see what she's actually pulling. 🙂