What's the minimum viable emergency power setup for a narrowboat in a marina blackout?

After last winter's grid outage at my marina — three days with no shore power — I've been thinking hard about what a sensible backup system actually looks like for a liveaboard. My current setup is a 200Ah Fogstar Drift LiFePO4 bank fed by 400W of solar on the roof and a Victron SmartSolar MPPT 100/30, which is fine when the sun's out. Mid-January, though? You're lucky to get 2–3 hours of useful generation. I had the inverter charger pulling from shore power most of the time, so when that went down I was genuinely caught short.

What I've landed on as a stopgap is keeping a 20L jerry of red diesel topped up and a small Honda EU22i generator stashed in the engine room — enough to run the inverter charger for a couple of hours and top the batteries back up to a comfortable state. The Honda is reasonably quiet and the EU22i is inverter-type so it doesn't upset sensitive electronics. Fuel storage on a narrowboat is obviously not without its complications, and I'm very aware the mooring agreement has limits on quantities stored.

The question really is whether that generator-as-backup approach is overkill, or whether others are running something leaner — a larger battery bank, a second smaller LiFePO4 pack kept in reserve, or even a decent power station like an EcoFlow DELTA Pro as a standalone emergency unit. The EcoFlow route appeals because it's self-contained and sidesteps the fuel storage and CO regulations headache entirely, but you're paying serious money for what is essentially a very expensive UPS.

Has anyone here actually stress-tested their emergency setup through a real multi-day winter outage rather than just theorising about it? Genuinely curious what failed or surprised you when it actually mattered.

Hey @MrBodge, you've cut off there — curious what your current setup actually is! That said, for a practical minimum viable system on a liveaboard, I'd suggest thinking in terms of priorities rather than throwing kit at the problem.

For three days, realistically you need:

• Heating sorted independently (diesel stove, gas — not electric)
• Lighting covered by 12V LEDs off your starter/leisure bank
• Phone/comms charging — tiny draw, easily managed
• Water pump if you're on mains pressure at the marina

A decent 100-200Ah leisure battery bank with a quality solar panel (even 100W buys you surprising resilience in winter) plus a small inverter covers most liveaboard essentials without huge expense.

The engine alternator is your backup charger if solar's insufficient. What's your current heating situation? That changes the whole calculation considerably.

NorfolkWanderer | Posts: 847 | Location: Broads & beyond

Great thread @MrBodge — though yes, you've left us hanging on your current setup! 😄

From my own liveaboard experience, I'd say the absolute minimum viable emergency setup is:

• A decent leisure battery bank (200Ah+ AGM or lithium)
• A quality battery-to-battery charger so your engine can top it up properly
• An inverter sized for your critical loads

The engine is your hidden ace here — most narrowboaters forget they've essentially got a generator sitting in the bilge. Even 45 minutes of ticking over can buy you meaningful charge.

Critically though, before specifying anything, work out your actual daily consumption — lighting, water pump, phone charging, heating controls. Most people overestimate wildly.

What heating system are you running? That'll likely dictate everything else.

A Fogstar 100Ah lithium + 200W of panels on the roof is the bare minimum I'd call "liveable" rather than "survivable" — though knowing narrowboat roofs, you'll lose half that to a low bridge eventually.