Anyone know if a 200W panel is enough to keep a 12V leisure battery topped up over winter?

Running a small garden office setup here and this question is keeping me up at night as we head into the darker months.

Currently have a single 200W Renogy mono panel feeding into a 100Ah Fogstar Drift LiFePO4 via a Victron SmartSolar MPPT. The office pulls maybe 150–200Wh a day — just a laptop, some LED lighting, and a small router.

Summer was brilliant, battery barely dipped below 90%. But now the trees around the garden are casting longer shadows and the sun is barely clearing the fence by midday. I'm starting to wonder if I've walked into trouble.

From what I've read, a 200W panel in the UK during December might only realistically deliver somewhere between 20–40Wh on a grim day — which is nowhere near enough to offset even modest consumption, let alone recover any deficit from previous cloudy days.

A few specific things I'm trying to work out:

• Is there a rough rule of thumb for winter panel output in southern England vs northern England? (I'm in the Midlands, so somewhere in between.)
• Would tilting the panel more steeply — say 60–70° — make a meaningful difference in November through February?
• Is a second 200W panel the obvious answer, or would I be better off adding more battery capacity to ride out bad spells?

Has anyone actually run data through winter on a similar-sized system? I've been poking around on PVWatts and pvgis.jrc.ec.europa.eu but translating those numbers into real-world "will the battery survive a grey week" confidence is harder than it sounds.

@CrispyWanderer mate, brutal truth — a 200W panel in a UK winter is basically a decorative ornament that occasionally does some work.

You're realistically looking at 1-3 peak sun hours on a good day (November through January is grim), so maybe 200-600Wh on a sunny day, potentially nothing useful for days on end during overcast spells.

For a garden office 100Ah Fogstar, I'd honestly suggest:

• Double up to 400W minimum if roof space allows
• Make sure your MPPT controller (Victron SmartSolar is worth every penny) is properly configured for winter voltage profiles
• Consider a small grid trickle charger as backup — even a basic Victron Blue Smart IP65 for the truly miserable weeks

Winter off-grid in Britain isn't a solar problem, it's a storage and backup strategy problem.

@BoatPaddy lol decorative ornament 😂 harsh but fair honestly

Right so — on my boat I've got similar panel wattage and in December/January you're looking at maybe 2-3 peak sun hours on a good day up here. Panel's often damp and mucky which kills output further.

200W sounds loads until you do the maths. You're realistically pulling maybe 30-40Ah on a decent winter day. If your office is pulling more than that you'll be in trouble within a week of grey skies.

My suggestion — if you can squeeze another panel on the roof, do it. Or look at a small backup charger from the mains for the grim months. Victron do decent smart chargers that play nicely with solar setups.

What's the actual consumption in the office? That's the bit nobody's mentioned yet

@BoatPaddy 😂 that's exactly what my narrowboat setup felt like last December — three days of solid grey and my 100Ah was basically flatlining!

Quick question for @CrispyWanderer though — are you running the garden office daily or just occasionally? Because if it's only a few hours a week, a 200W panel might scrape by with careful usage management. But if you're in there all day working, I'd genuinely be looking at adding a second panel or at least a small backup charger from the mains for the grim weeks.

What's your actual daily consumption looking like? That figure matters so much more than the panel wattage alone when you're trying to work out if you'll end up in trouble come January.

@BoatPaddy's "decorative ornament" is doing real work on my conscience because I've lived that exact scenario — shepherd's hut, December, south-facing 200W panel, and my Victron BMV telling me progressively more depressing things each morning.

What saved me wasn't more panels (though eventually yes), it was getting ruthless about consumption profiling first. Knowing exactly what was draining overnight changed everything. Turns out my little inverter had a vampire draw I'd completely ignored.

@CrispyWanderer — garden office is interesting because you likely have predictable usage patterns unlike a boat moving about. Log your actual daily consumption for a week, then check pvgis.ec.europa.eu for your postcode's December irradiance figures. The maths will either reassure you or properly terrify you, but at least you'll know rather than just worry.