Anyone know if a 200W panel will keep a 100Ah leisure battery topped up over winter?

So I've been scratching my head over this one for a while and figured someone here would know the maths better than me.

Running a Victron SmartShunt on a 100Ah AGM leisure battery that powers my LDV Camper's basic loads — a 12V compressor fridge, some LED lighting, and a Webasto heater controller. Nothing exotic.

I've got a single 200W panel (one of the Renogy mono ones) mounted flat on the roof, which is the problem — no angle adjustment possible with my setup.

Summer has been brilliant, battery barely dips below 90%. But now we're staring down the barrel of a UK winter and I'm genuinely unsure whether 200W horizontal in, say, Yorkshire in December is going to be anywhere near enough to offset even modest daily loads.

From what I can gather, you're looking at maybe 1-2 peak sun hours on a good winter's day this far north, so realistically pulling perhaps 150-250Wh on a clear day? My fridge alone is probably chewing through 300-400Wh daily depending on ambient temperature.

A few specific questions:

• Is my peak sun hour estimate roughly right for northern England?
• Would adding a second 100W panel make a meaningful difference, or would I be better off looking at a bigger battery bank to ride out cloudy stretches?
• Does anyone run a similar setup through winter successfully, or is shore power / a B2B charger from the vehicle just the realistic answer?

I do have access to hook-up probably twice a week, so it's not a complete disaster either way — just trying to minimise reliance on it.

@LDVCamper short answer: probably not on its own, not reliably anyway.

Over winter in the UK you're realistically looking at 1-2 usable sun hours on a good day, often less. A 200W panel might only deliver 30-50Ah on a decent December day — and that's assuming no shading, good angle, clean panel.

The bigger issue is your SmartShunt will tell you exactly how screwed you are 😄 — worth checking your actual daily consumption figure first.

What's your typical draw? If you're running lights and a 12V compressor fridge that changes everything vs just USB charging and an occasional light.

A 40A DC-DC charger fed from the van alternator is what saved my winters honestly. Panel as backup, alternator as the workhorse.

@NickHughes is right, and your SmartShunt will make the disappointment beautifully data-rich — nothing like watching 4% State of Charge on a graph while the rain hammers down on your 200W panel that's performing more like a damp 40W flannel.

Spent last November on the boat learning exactly this lesson the hard way. Added a Victron Orion DC-DC charger hooked to the engine alternator and suddenly winter wasn't a crisis anymore — even a short run sorts you out.

If driving isn't an option, a small Fogstar lithium swap would stretch that 100Ah considerably further on the same panel input, since you're actually using the full capacity rather than tiptoeing around AGM's 50% ceiling.

@LDVCamper worth looking at this from a consumption angle rather than just generation. What's your actual daily Ah draw? Because a 200W panel in December across most of the UK is realistically giving you maybe 1-2 peak sun hours on a good day — so call it 20-40Ah theoretical maximum, minus controller losses.

If you're pulling more than that daily, you're in deficit regardless.

I run a similar setup on the boat over winter — 300W of Victron panels and I still hook up to shore power periodically November through February. The SmartShunt historical data is genuinely eye-opening; you can see exactly when the trend turns negative.

One practical tip: tilt your panel steeper in winter — closer to 60° rather than summer's flat angle. Makes a meaningful difference at low sun elevation angles, especially if you're not in the south.

@LDVCamper done this exact battle on my narrowboat — a 200W panel in December is basically a 30-40W panel once you factor in short days, low sun angle, and British cloud (so roughly 0.5–1 peak sun hours daily up north).

That gives you maybe 15–40Wh on a good day, which won't touch the sides if you're running a fridge or heating controls.

Practical fix: pair it with a decent Fogstar Drift LiFePO4 if budget allows — the flat discharge curve means what little solar you do harvest actually counts properly, unlike AGM which sulks in winter.

@ForestBoater's point is the real one though — know your Ah draw first, or you're just guessing in the dark (literally, by January).