Narrowboat solar setup — is 400W enough for liveaboard with EV charging ambitions?

Finally pulled the trigger on a proper solar install for the boat after running on the engine alternator alone for two years. Currently have 2x 200W Renogy panels on the roof feeding a Victron SmartSolar 100/30, going into a 200Ah Fogstar Drift lithium. Runs the 12V lighting, a small inverter for the laptop, and the 240V fridge no problem through spring and summer.

The issue is I'm also using a small EV (Renault Zoe) at the marina and I'm fantasising about trickle-charging it from the boat rather than paying the marina's extortionate hook-up rates. Even 6A through the Type 2 socket overnight would make a dent. Realistically I know 400W of solar plus a 200Ah bank isn't going to cut it for that — but I'm trying to work out what would.

Has anyone actually done EV charging from a narrowboat system? I'm thinking I'd need to at least double the battery bank and probably add another 400W of panels, but the roof space is genuinely limited — especially with the cratch cover taking up the front section. Wondering if flexible panels on the cratch or cabin sides are worth it, or just a waste of money.

What are people actually running for higher-demand liveaboard setups? Curious what the realistic floor is for making EV trickle-charging viable without running the engine every other day.

@VanSue the short answer is: 400W will keep your domestic bank happy on a good summer day, but EV charging will laugh in your face.

I've been through exactly this on my own narrowboat. The maths are brutal — even a modest 3.6kW Type 2 charge adds up to roughly 9x your entire array output running flat out. You're not generating that afloat, full stop.

What I eventually settled on was treating EV charging as a marina-only activity, plugged into shore power, whilst the solar handles everyday 12V loads entirely.

If you're serious about integrating the two properly, the Victron SmartSolar MPPT would need pairing with a much larger array — realistically 800W minimum — plus a decent inverter-charger setup. Even then, expect it to take days not hours.

What's your battery capacity currently?

@VanSue I lived this exact dilemma before I sorted my cabin setup. The brutal truth is that EV charging via solar alone on a narrowboat roof is a fantasy unless you're moored up for days at a time in July.

What actually works is treating them as separate problems — solar handles domestic loads beautifully, but EV top-ups happen at marina hookups or a dedicated shore power session. Fighting that reality will just leave you frustrated.

If you're serious about onboard EV charging, look at upgrading to a Victron Multiplus rather than throwing more panels at it. You'd then be able to pull from hookup and your battery bank simultaneously, which is genuinely useful on darker months.

400W is a solid domestic foundation. Don't let EV ambitions make you undervalue what you've already got.

MIA_VanLife | 847 posts | ⚡ Solar Enthusiast

@VanSue what's your EV situation exactly — are we talking topping up a small city car occasionally, or daily commuting distances? That changes the maths enormously.

As @SophieFisher and @InverterQueen are hinting at, solar-to-EV is really a "bonus charging" game rather than a primary strategy on a narrowboat roof. Your 400W will struggle to push meaningful kWh into a car battery without seriously compromising your domestic loads.

What I'd actually look at is running your EV charging opportunistically — marina shore power when you're moored up, combined with solar keeping the domestic bank healthy so you're not also drawing down for lighting, fridge etc.

Have you got space for a third panel? Even 600W total shifts the conversation a bit. What's your battery bank capacity currently?