Tiny cabin on a narrowboat plot — what's a realistic solar setup for year-round UK use?

Planning a small off-grid cabin on a mooring plot in the East Midlands. Footprint's about 20m², so loads are modest — LED lighting, 12V fridge, laptop, phone charging, maybe a small 240V inverter for power tools occasionally. Rough daily estimate is around 600–800Wh in summer, but winter's the real concern obviously.

Been running a Victron SmartSolar 100/30 with 400W of panels on my narrowboat for a couple of years and it's solid, but a static cabin is a different beast — no engine alternator as backup, and I'm not there every day to monitor it. Thinking of scaling up to maybe 600–800W of panels and a proper LiFePO4 bank, probably 200Ah from Fogstar.

The winter shading is what's worrying me. The plot has trees to the south-west and December sun angles are brutal up here. Wondering whether a generator top-up is just unavoidable, or whether anyone's cracked year-round purely solar in the UK Midlands without losing their mind over it.

Has anyone sized a cabin system specifically for UK winter and actually got the data to back up what worked? Interested in real kWh figures, panel tilt angles, whether you went east-west split — anything concrete really.

Kingy74 | Senior Member

@CaddyProject nice project! One thing worth flagging for East Midlands specifically — you'll hit some grim solar windows November through January, sometimes only 1-2 peak sun hours a day. I'd seriously consider oversizing your panel array rather than your battery bank to compensate. Something like 600-800W of panels feeding a decent 200Ah lithium setup would serve you far better than going 400W panels with a massive battery. The panels earn their keep on those bright but short winter days.

Also worth thinking about a small wind turbine as a complement — the Midlands can be pretty breezy and it'll tick away overnight when solar does nothing. A 400W turbine alongside your solar is a genuinely solid combo for year-round resilience rather than just managing your consumption down to nothing all winter. 🙂

DanPhillips | Member

@CaddyProject great little project! One thing I'd add to what @Kingy74 is getting at — don't underestimate how brutal December and January are for solar in the Midlands. You're looking at sometimes only 1-2 peak sun hours on overcast days, which can stretch for weeks. For year-round reliability I'd seriously consider a small wind turbine or a backup generator rather than oversizing your panels massively trying to compensate.

A 400-600Ah LiFePO4 bank with 600-800W of panels is a reasonable starting point for your loads, but having a 1000W petrol genny for the odd winter top-up keeps your battery from sitting chronically low and degrading. Budget for a decent MPPT controller too — makes a real difference in those marginal light conditions we get up here.

RobJones85 | Member

Running something similar in my motorhome year-round so fairly relevant. Biggest thing people underestimate is Nov-Feb — you're looking at maybe 1-2 peak sun hours on a bad week in the Midlands. I'd size the battery bank for 3-4 days autonomy minimum, not the usual 1-2 day advice you see online.

For a 20m² cabin I'd probably go:

• 400-600W panels (more than you think you need)
• 200Ah+ LiFePO4 — Fogstar Drift cells are decent value
• Victron MPPT — non-negotiable for the marginal winter gains

Don't cheap out on the MPPT controller thinking it's just a regulator. In December every amp counts.

EllaPalmer | Member

Great project @CaddyProject! One thing nobody's touched on yet — with a 20m² footprint you'll likely have limited roof space, so panel placement and angle become really important. A fixed tilt of around 35–40° will give you the best year-round compromise in the East Midlands rather than optimising purely for summer. Also worth thinking seriously about a decent wind turbine as a complement to solar, since winter UK days are so short and often overcast. Even a small 400W turbine can make a real difference between November and February when your panels are producing next to nothing. For battery storage I'd suggest sizing generously — probably 200Ah+ of lithium if budget allows, given you've got a 12V fridge running continuously. That's your biggest sustained draw by some margin.

GazPrice | Member

Built out a shepherd's hut setup a couple of years back, similar load profile to what you're describing. One thing worth flagging for East Midlands specifically — November through February is brutal for solar yield. I'd lean toward a larger battery bank rather than throwing more panels at it.

Minimum I'd suggest: 400Ah LiFePO4 (Fogstar Drift cells are decent value) paired with a Victron SmartSolar MPPT. Don't cheap out on the controller — the Victron app for monitoring winter performance alone is worth it.

Also seriously consider a small wind turbine as a secondary source. East Midlands gets reasonable wind and it actually produces when solar doesn't. The two complement each other well through winter months.

What's your hookup situation for backup charging? That changes the battery sizing conversation quite a bit.