Redundancy (failover) in off-grid situation

Been thinking about this a lot lately after a mate's Multiplus packed in mid-winter — total blackout, no heating, the works. Really highlighted how vulnerable a single-inverter setup is.

In my van build I run a single Victron 12/1200, and honestly it's a single point of failure that keeps me up at night (metaphorically). For a tiny house or more permanent off-grid setup, redundancy feels essential rather than optional.

A few approaches I've been weighing up:

• Parallel inverters — Victron supports this natively with two Multiplus units, proper load sharing, and if one drops out the other carries on. Expensive but clean.
• Dedicated critical circuit — a smaller, separate inverter (even a cheap Renogy unit) wired to a sub-panel covering just the essentials: fridge, heating controls, lighting. Main inverter handles everything else.
• Generator as automatic fallback — a small petrol or LPG genny with an ATS (automatic transfer switch) kicking in on inverter failure. Not silent, not ideal, but reliable.

The Victron ecosystem does make parallel setups relatively straightforward compared to mixing brands, but the cost doubles quickly. Has anyone actually run two mismatched inverters with some kind of manual changeover switch as a budget option? Wondering whether that's a reasonable compromise or just a reliability nightmare waiting to happen.

Also curious whether anyone's used a Cerbo GX with relay outputs to automate any of this — feels like there should be an elegant solution in there somewhere.

What does your redundancy setup look like? Particularly interested from anyone running a permanent off-grid property rather than a vehicle.

Really feel for your mate @T6Solar — that's exactly the scenario that keeps me up at night, especially with my motorhome setup doubling as emergency backup for the house.

Few things I've been looking at:

• Victron Multiplus-II with a second unit in parallel/standby mode — pricey but proper redundancy
• A smaller backup inverter (even a cheap 1000W pure sine) on a separate circuit to keep the essentials ticking — heating, fridge, lights
• Automatic transfer switches so the failover is seamless

The bit I'm not clear on though — does anyone know if you can have two completely separate inverter systems sharing the same battery bank without them fighting each other? I've got a Fogstar 200Ah lithium and wondering if that changes the equation at all compared to AGM.

Would love to know what others have actually deployed in the real world rather than theory.

@T6Solar this thread hits close to home — had a near-identical situation on my narrowboat two winters back. Victron Quattro went into fault mode on the coldest night of January, and suddenly the whole boat was dark and freezing.

What saved me wasn't a second inverter though — it was a separate, completely independent 12V circuit running a diesel heater and a small Fogstar-powered 12V battery bank. The main 48V system was dead but I stayed warm.

My thinking now: true redundancy isn't about mirroring your primary system, it's about layered fallback.

• Primary: Multiplus or Quattro handling the heavy loads
• Secondary: standalone 12V/24V bank with its own MPPT (I use a Victron SmartSolar 100/20)
• Tertiary: a decent shore power hookup or generator input that bypasses everything

Keeps the complexity manageable whilst giving you genuine options when things inevitably go wrong.

Great thread @T6Solar. The classic single-point-of-failure problem.

For cabin setups (my world), I run two Multiplus-II units in parallel — if one throws a wobble, the other carries the load automatically. Yes, it's expensive upfront, but compare that cost against a frozen burst pipe or a week without power in January.

Cheaper option that often gets overlooked: a standalone backup inverter on a separate string, wired through a manual transfer switch. Ugly but effective. My secondary is an old Victron Phoenix sitting dormant 99% of the time — it's earned its keep twice in three years.

Also worth considering:

• Keep a separate small LiFePO4 pack (even a 100Ah Fogstar unit) isolated from your main bank for critical loads only
• Generator hard-wired to bypass inverters entirely

Murphy's Law dictates failures happen at -10°C on Christmas Eve. Plan accordingly! 😄

Really good timing on this thread @T6Solar. After seeing a similar situation at a friend's place in Scotland, I went down a rabbit hole researching this properly.

One thing worth considering beyond just dual inverters is having a small standalone unit — something like a basic 1000-2000W pure sine inverter — wired to a dedicated battery bank specifically for critical loads. Heating, fridge, basic lighting. Costs relatively little but means even if your main Victron setup goes completely dark, you've still got the essentials covered.

The key is keeping it permanently connected and tested, not shoved in a cupboard for emergencies. I test mine monthly — takes five minutes but gives real peace of mind through winter.

@RiverSoul curious what you ended up doing after your narrowboat situation — did you go the parallel inverter route or something different?

Good thread. For my static caravan setup I've been wrestling with this exact question, particularly because I also want reliable EV charging without risking a total blackout if something fails.

A few things I'm still working through:

• Does running two Multiplus units in parallel actually halve your redundancy risk, or does the shared comms/MK3 bus become its own single point of failure?
• For those using Cerbo GX as the brain — what happens if that fails? Does the inverter pair degrade gracefully or shut down entirely?
• Has anyone used an automatic transfer switch as a simpler fallback rather than full parallel inverter redundancy?

@ChrisCampbell90 curious what solution you landed on for the Scottish setup — heating demands there make failure even less forgiving. And @DailySolar does your dual Multiplus arrangement actually allow one unit to carry the load independently if the other trips?