Adapting my van solar setup for a narrowboat — what am I missing?

After three years running a 400W rooftop array on my Ducato with a Victron SmartSolar MPPT 100/30 and a 200Ah Fogstar Drift LiFePO4, I've been asked to help a friend install something similar on their 58ft narrowboat. On paper it seems straightforward, but I'm quickly realising the marine environment throws up some complications I haven't had to think about.

The main difference I keep coming back to is the roof geometry — the boat has a curved, cluttered cabin roof with vents, exhausts, and a cratch cover eating into the usable space. We're probably looking at 300W max across two 150W panels laid flat, which is going to hammer the yield compared to even a modest tilt. The Victron kit should carry across fine, and I'd planned on a 100Ah Battle Born or equivalent LiFePO4 to start, but I'm second-guessing whether flat-mounted panels on a steel hull with potential shading from a tow path's tree canopy is going to produce anything useful on a cloudy UK summer day.

The other thing I'm not sure about is bonding and earthing on a steel narrowboat. On my van the chassis is the negative return, but I've read that on steel-hulled boats you want to be very careful about stray current corrosion — potentially isolating the solar negative entirely rather than bonding to the hull. Has anyone actually run Victron kit on a narrowboat and dealt with this properly, or is it a case of calling in a qualified marine electrician regardless?

Also curious whether anyone has experience with flexible vs rigid panels in this context. The roof gets walked on regularly for lock-keeping, so rigid panels with proper edge guards might be a hazard, but I've seen mixed reports on the longevity of flexible panels in UV-heavy outdoor installs.

@DucatoSolar biggest thing people forget going van-to-boat is that narrowboats are basically floating caravans that also need engine alternator charging sorted properly. Your Victron kit will handle it fine but you'll want a Battery-to-Battery charger in the mix — Victron Orion-Tr Smart is the obvious choice.

Hamish1980 | 847 posts

Good timing on this thread! One thing I'd add that nobody's touched on yet — shore power integration is far more relevant on a narrowboat than a van. Most marina moorings offer hook-up, so make sure you're thinking about a proper AC charger (Victron MultiPlus or similar) that plays nicely alongside your MPPT.

Also worth considering: canal orientation means you're often moored bow-to-bank with trees either side, so shading can be a genuine issue far more than on a van roof. Flexible panels flush-mounted on a curved cabin roof will suffer more from partial shading than you might be used to — might be worth looking at whether your MPPT setup handles that well or whether panel layout needs rethinking.

What's the boat's existing 12V or 24V setup looking like? That'll affect a lot of decisions. 🚢

@DucatoSolar also worth thinking about alternator charging from the engine — narrowboats run their engine way more than vans do, often daily for heat and water pumping. A proper DC-DC charger (Victron Orion-Tr Smart is the obvious choice) between the engine battery and your LiFePO4 bank will do far more work than you'd expect.

Also the load profile is completely different — a boat's got a bilge pump, navigation lights, maybe a diesel heater blower. Run a proper audit before sizing anything.

One more thing — shading from bridges and trees hits narrowboats constantly, especially on the canals. Worth considering if your friend moves around a lot vs being moored up permanently.

Been down this exact rabbit hole when I toyed with putting solar on my own narrowboat before settling on the motorhome instead.

The thing nobody warns you about is canal orientation. On a van you park facing the sun. On a narrowboat you're at the mercy of which way the cut runs — I've watched friends moor up with their entire roof in shade from the towpath trees for days.

Factor that into your sizing calculations heavily. Your mate's 400W might need bumping considerably just to account for the rubbish angles and tree cover you simply don't get on a campsite.

Also — and this is critical — roof walkability. Narrowboat roofs take a battering from people clambering over them. Those panels need proper recessed mounting or you'll be crying over cracked cells before the season's out.

DeclanKnight57 | 203 posts

One thing nobody's flagged yet — corrosion is brutal on a narrowboat compared to a van. Canal environment is way more humid than you'd think, even just moored up. All your cable terminations, connectors, fuse holders — worth using proper marine-grade stuff throughout rather than the automotive bits you'd normally reach for.

Also your MPPT placement matters more. In a Ducato you can tuck it anywhere dry, but on a narrowboat the engine bay gets damp and the cabin can too. Victron kit handles it better than most but still worth thinking about where it's actually going to live long-term.

@DucatoSolar the 100/30 should be fine capacity-wise for a similar array, just double-check the cable runs — narrowboats can be surprisingly long.

Good shout from @DeclanKnight57 on corrosion — canal environment is genuinely harsh.

One thing I'd add from my solar experience: roof shading is a completely different beast on a narrowboat. Trees on towpaths, bridges, lock structures — you're constantly getting partial shade in a way that barely happens on a van moving down open roads.

Worth considering multiple smaller strings rather than one big array, so shade on one panel doesn't kill your whole output. The Victron SmartSolar handles this better than most but it's not magic.

Also check your friend's roof curvature — narrowboat roofs often have a gentle crown that complicates flush mounting. Tilt brackets help but add wind resistance and snag on low bridges.

Good points all round. One thing I'd flag that's different from a van install — roof flex and movement on a narrowboat is a real thing. The hull shifts as it moves through water, especially on busy stretches. Worth using proper marine cable glands rather than just grommeting through the roof like you might on a Ducato, and silicone everything twice over.

Also, shading from bridges and locks is way more frequent than you'd expect on canals. Might be worth considering whether that 100/30 is still the right size if your friend wants to expand the array later.

RussMitchell75 | 847 posts

Great thread. One thing I haven't seen mentioned yet — shore power integration. Most narrowboats will be hooking up at marina moorings regularly, so make sure your friend's system is set up to handle that alongside the solar. A decent inverter-charger rather than a standalone inverter is worth the extra outlay here. Victron's MultiPlus range plays very nicely with the SmartSolar your mate's already familiar with from the van world, and the VE.Bus integration makes managing both charge sources genuinely seamless. Worth planning for from the start rather than retrofitting later. 🚢