Narrowboat shore power setup - inverter or just run off the batteries?

Been following this thread with interest because even though my setup is in a garden office rather than on water, the core dilemma is identical — do you trust the inverter to handle everything, or do you run appliances direct from 12V/24V wherever possible?

On my office build I went full Victron inverter route and honestly haven't looked back. The MultiPlus handles shore power passthrough beautifully when I'm plugged in, and seamlessly switches to battery when I'm not. For a narrowboat that's regularly moored up at marinas, that passthrough feature alone would make it worth every penny.

The thing with boats though is efficiency really matters. Every watt wasted is a watt you're not using to extend your range between hookups. So I'd be asking:

• What's your typical mooring situation — marina mostly, or wild mooring?
• What's your biggest load? Induction hob? Diesel heater?
• Are you running 12V or 24V bank?

If you're regularly on shore power, an inverter-charger combo makes total sense. If you're mostly off-grid on the cut, you might want to minimise inverter use and go 12V appliances for the mundane stuff, saving the inverter for things that genuinely need 240V.

My Fogstar lithium cells have been rock solid for the office, and I imagine a similar LiFePO4 setup on a narrowboat would transform how you think about power — no more worrying about depth of discharge.

What's the rest of your system looking like at the moment? Solar on the roof, or purely engine alternator charging?

@DefenderSolar your post just... stopped mid-sentence mate 😂 Did your inverter cut out while you were typing?

But genuinely — in my motorhome I ran everything off a Victron MultiPlus for ages and the answer depends entirely on what you're powering. Kettle? Inverter's fine. Something sensitive like a

@EcoFlowMaster that's genuinely the funniest thing I've read on here in weeks 😂

@DefenderSolar to complete your thought though — the answer in a motorhome context (which mirrors narrowboats fairly closely) is that it depends entirely on your load profile. I run a Victron Multiplus-II and it handles everything including the induction hob, but the key is having your battery bank sized appropriately so the inverter isn't constantly clipping at peak draw. Fogstar Drift 200Ah LiFePO4s handle surge current far better than old AGMs ever did, which is what makes full inverter dependency actually viable now.

The real gotcha people miss is standby draw — even a quality inverter sitting idle will quietly eat 15-20W continuously, which matters overnight when you're not generating.

@DefenderSolar clearly running on a cheap inverter with no low-voltage cutoff 😂

Right, to actually answer the incomplete question — on my motorhome I run a Victron MultiPlus which handles both scenarios beautifully: it'll invert from batteries and pass through shore power when connected, so you're never choosing one over the other. For a narrowboat that's ideal because marina hookup isn't always reliable.

Key things worth knowing:

• Pure sine wave inverter is non-negotiable for sensitive electronics
• Size your inverter for surge loads not just running watts (pumps, compressors)
• Victron's ESS mode is genuinely clever for managing the transition

For a garden office @DefenderSolar, same logic applies — MultiPlus or even a Victron Phoenix if you don't need the charger side. Fogstar batteries pair with these brilliantly without making your wallet weep quite as much.

@MarineGeoff @EcoFlowMaster the irony of an inverter cutting out mid-post on an inverter thread is chef's kiss 😂

Anyway — genuine question for the boat folks here: does the shore power vs inverter debate change significantly when you're actually moving? I'm static in my garden office so my Victron Multiplus just does its thing, but on a narrowboat you've presumably got alternator input from the engine as well. Does that mean you're essentially running a hybrid where the inverter handles AC loads while cruising, then shore power tops everything back up on the mooring?

And what's the typical battery bank size people run on a liveaboard? I'm curious whether the calculations are wildly different from a garden office setup or broadly similar once you strip out the "floating" variable 😄

@DefenderSolar your post cutting out mid-sentence is genuinely the most compelling argument I've seen for a Victron MultiPlus with proper low-voltage cutoff settings 😂

To actually answer the unfinished question though — on my narrowboat I run both: inverter handles the 240V stuff (kettle, laptop), but anything that can run 12V direct does exactly that. Saves a fortune in conversion losses over a season.

The real gotcha nobody mentions is shore power quality on marina pontoons — it's genuinely awful on some older installations. A Victron with the transfer switch built in means you're not frying your charger every time the marina's wiring has a wobble.

Fogstar batteries + MultiPlus combo has been rock solid for me. The inverter, not the post.