Fitting solar to a narrowboat — is 200W enough for a liveaboard weekend?

Planning to put a basic solar setup on a friend's narrowboat for weekend trips. She's not living aboard full-time but wants to run LED lighting, a 12V compressor fridge, phone/laptop charging, and maybe a small inverter for a kettle occasionally. Thinking 200W panel (probably a flexible Renogy unit given the curved roof) feeding into a Victron SmartSolar MPPT and a pair of 100Ah AGMs.

The fridge is the obvious killer — probably 40-50Ah/day on its own. Add lighting and device charging and I'm guessing 70-80Ah total daily draw. Two 100Ah AGMs gives maybe 100Ah usable at 50% DoD, so on a decent summer day the solar should keep pace, but I'm a bit nervous about cloudy stretches or back-to-back weekends without shore power.

Tempted to suggest upgrading to a single 100Ah lithium (Fogstar Drift maybe) instead of the AGMs — better DoD, lighter, and she wouldn't be dragging a massive bank around. But the narrowboat already has a decent alternator on the engine, so the AGMs might actually be fine given she'll be cruising a fair bit.

Has anyone done a similar setup on a narrowboat? Curious whether 200W genuinely cuts it on the cut ☀️, or whether we're underspeccing from the start.

Lisa1978 | 📍 West Midlands | ⛵ Narrowboat owner

Hamish, I'd honestly say 200W will struggle once you factor in that compressor fridge — mine draws around 4-5 amps continuously, which adds up quickly over a weekend, especially if you're moored under trees or it's a grey October. I run 400W on Marguerite and still occasionally have to be careful in winter.

One thing people often overlook with narrowboats specifically is the roof space constraint — you might physically fit 200W but have room to expand later if you plan the cabling properly now. Worth oversizing your controller and cable runs from the start.

What's the battery bank looking like? That'll honestly matter more than the panel wattage for a weekend setup. A decent 100Ah lithium will outperform 200Ah of leisure lead-acid every time. 😊

DuctTapeDave62 | 📍 Yorkshire | 🔧 12 years off-grid

Totally agree with @Lisa1978 that 200W will be tight. The compressor fridge alone will likely chew through 30-50Ah daily depending on ambient temp, and that's before you've touched the laptop or lighting. On a narrowboat you've also got the added complication of shade from trees and canal-side buildings — you'll rarely see full rated output. I'd suggest pushing to at least 300-400W if roof space allows, and make sure the battery bank is properly sized to match. Are you planning AGM or lithium? That choice will significantly affect what you can realistically draw down. Also worth mentioning — what's your inverter situation for the laptop? That's often where people underestimate their consumption.