Fitting solar to a narrowboat — where do I even start with the roof layout?

Finally pulled the trigger on getting some panels on my 57ft narrowboat after running a noisy generator for too long. The roof space looks generous until you account for the cratch cover, mushroom vents, and the chimney — suddenly it's a lot more awkward than I expected.

I'm thinking 2–3 x 200W panels (Renogy or similar) feeding into a Victron MPPT, with a modest 200Ah lithium bank (probably Fogstar Drift) to start. The boat is used mostly at weekends and the odd extended cruise, so I'm not trying to run a full off-grid homestead — just fridge, lights, phone/laptop charging, and maybe a small inverter for the occasional 240V need.

A few things I'm genuinely unsure about:

• Series vs parallel wiring on the panels given partial shading from the chimney
• Whether a tiltable mounting system is worth the hassle on a canal boat (wind loading concerns?)
• Any marine-rated cable and connector recommendations for running the cables down into the boat

Has anyone actually done this on a narrowboat rather than a sea-going vessel? Feels like a lot of the advice online assumes either a yacht or a campervan, and the narrowboat situation seems quite specific.

Mike1986 | 847 posts

@T6Project welcome to the rabbit hole! One thing people often overlook before drawing up their roof layout is actually logging their daily consumption first. Spend a week noting down everything — inverter loads, 12v lighting, the pump, fridge if you've got one — because that dictates how much generation you actually need, which then tells you whether you're fitting 2 panels or 6.

Also worth measuring your usable roof in person with a tape rather than relying on boat specs. My mate did a 57ft and lost nearly 8ft once he properly accounted for the cratch, mushrooms, and a blacking point near the stern hatch.

What's your battery bank situation currently? That'll shape the conversation massively — no point cramming 800W on the roof if your batteries can't absorb it properly.

LizWalker | 312 posts

@T6Project Congratulations on making the switch! One thing worth doing early on is spending a day photographing your roof at different times — you'll quickly spot where shadows fall from the exhaust flue, handrails, and any tunnel lamp fittings. Shading on narrowboats is trickier than houses because you're often moving, so the sun angle shifts constantly throughout the day.

Also bear in mind that panels mounted flat (or near-flat) on a narrowboat roof will underperform compared to a tilted installation, so factor that into your sizing calculations. Many boaters here go slightly larger than they think they need for exactly that reason.

What's your rough daily consumption looking like? That'll help work out whether you're talking two panels or six. 😊

Midge55 | 203 posts

@T6Project Before you get too attached to any layout, walk the roof at different times of day and watch where shadows fall from the chimney and any handrails. On a narrowboat those shadows track across the roof as you change heading, which matters more than people realise — a shaded cell can drag down a whole string depending on your wiring configuration. Worth considering MPPT controllers with individual panel optimisers, or at least planning your strings so shadowed panels don't kill your best producers. Also measure your roof camber carefully — some panels don't sit flush on a curved roof without proper mounting frames, and you don't want water pooling underneath causing rust. What's your rough daily consumption looking like? That'll help work out whether you're realistically planning for leisure mooring top-ups or genuine continuous cruising independence, as the answer changes your battery sizing quite significantly.

EllaDixon71 | 156 posts

@T6Project Great decision! One thing nobody's mentioned yet — think carefully about panel orientation relative to your typical mooring spots. If you predominantly moor up facing a particular direction (many of us end up with favourite spots or regular visitor moorings), you might find angling your layout slightly to favour one side pays dividends. Also worth considering tiltable mounting frames; on a flat roof they can make a surprising difference to winter output when the sun's low. We fitted two 200W panels on tiltable mounts on our 60-footer and honestly the winter generation improvement was worth every penny. Don't forget to factor in where your cable runs will drop down into the boat — drilling through the roof properly with good waterproofing is critical, not an afterthought!

ST_Builds | 156 posts

@T6Project one thing specific to narrowboats that catches people out — portrait vs landscape orientation matters a lot on a narrow roof. Most boats are only about 6ft 2" wide usable, so landscape-mounted panels often work out better than you'd think, letting you run a longer string without the width constraint biting you.

Also worth checking whether you want a tilt kit. Flat-mounted panels on a boat that's moored east-west for weeks at a time can really underperform. Did exactly this on a mate's 60-footer with some Renogy 200W panels and we ended up adding tilt legs — made a noticeable difference.

What battery bank are you planning? If you're going lithium the Victron MPPT controllers handle the charge profile properly, worth factoring that into the layout early rather than retrofitting.

TH_OffGrid | 412 posts

@T6Project Worth getting your head around the 57ft constraint early — you've basically got a long thin strip to work with, and the usable rectangle is narrower than most people expect once you factor in handrails and the towpath walking route. On a boat that length I'd seriously look at 4x 200W panels in two parallel strings of two rather than chasing a single large string. Gives you better flexibility if partial shading hits one side (trees, lock structures, bridge holes). Also, what's your battery bank looking like? There's little point optimising the roof layout without knowing your storage capacity and what charge controller you're planning — MPPT is a must on a boat, full stop. What's your typical daily consumption roughly?