Anyone else using their van build as a backup for home power during outages?

My tiny house setup got me thinking — I've got a Victron Multiplus 12/3000 in the van and a decent Fogstar Drift 200Ah lithium bank. During the last big storm we had, mains went down for about 14 hours and I just ran an extension lead from the van parked on the drive. Kept the fridge, router and a few lights going no bother.

Obviously it's not a proper whole-home UPS, but for emergency backup it's surprisingly capable. The van charges back up via the solar panels (3x 175W Renogy) on a decent day, so it's not just sitting there being useless between trips.

Curious whether anyone else has done this deliberately — as in, actually planned their van electrics around the dual-use case? Wondering if it's worth upsizing the battery bank to maybe 300–400Ah so it covers a longer outage without needing the solar to catch up mid-crisis.

@RockyTinker interesting concept, though my experience is from the static caravan end rather than a van build.

The key practical issue I'd flag is cable run length — if your van is parked any distance from the house consumer unit, voltage drop on a 12V system becomes genuinely problematic at 3000W loads. Worth calculating properly before relying on it in an emergency.

The Multiplus 12/3000 will also struggle with inrush current from anything motor-driven — fridges, pumps, that sort of thing — more so than a 24V or 48V equivalent would.

Have you considered running the Multiplus in inverter-only mode with a properly fused extension lead feeding a ring of sockets rather than attempting a full consumer unit tie-in? Far simpler legally and practically, and avoids any DNO complications around backfeeding.

@RockyTinker yes, done exactly this with my shepherd's hut setup — the van essentially became a mobile UPS during a 14-hour outage last winter.

Few practical points worth raising:

• Shore power lead into the house works fine but watch your cable ratings — a proper 16A hookup lead is essential
• The Multiplus inverter transfer switch is near-instant, so fridges and sensitive kit survive the changeover without complaint
• Keep an eye on your State of Charge — 200Ah sounds generous until you're running a fridge, phone chargers, and a few lights overnight

The bigger limitation I found was solar recharge being slow in January. If you're relying on this regularly, a small generator for backup charging is worth considering rather than just hoping for sun.

What's your solar panel situation on the van? That changes the picture considerably.

Great thread @RockyTinker — I've been doing something similar up here in the Lakes where outages aren't exactly rare!

One thing worth mentioning that nobody's touched on yet: if you're running the Multiplus as a proper backup, make sure you've got a decent transfer switch or at least a solid physical separation from the grid feed before you plug into the house consumer unit. Last thing you want is back-feeding during an outage — DNO engineers working on the lines won't thank you for it.

@WingAndPrayer's 14-hour run sounds about right in my experience too. With a 200Ah bank at 12V you're realistically looking at maybe 1.5-2kWh usable, so prioritising what you run is key. Kettle and fridge yes, electric shower absolutely not! 😄

What gauge cable are you running from the van to the house?

Really intrigued by this thread — I've been pondering something similar with my motorhome but hadn't considered it as a deliberate backup strategy, more just a happy accident waiting to happen.

Quick practical question though: what are people actually using to connect the van's inverter output into the house circuits? Are you just running extension leads to critical appliances, or has anyone done something more permanent like a transfer switch or a proper changeover arrangement at the consumer unit?

I've got a Victron Multiplus setup in mine and the solar/charging side is sorted, but the "last mile" into the house feels like the fiddly bit where things could go wrong — or worse, go unsafe. Wouldn't want to backfeed anything onto the street network.

@WingAndPrayer curious how you handled it on the shepherd's hut — presumably similar challenge?

Really useful thread this. I've got a similar dilemma — my boat setup has a Victron SmartShunt and 200Ah Fogstar bank, and I've often wondered whether I could run an extension lead from the boat (moored nearby) into the house during an outage.

Anyone done this practically? My concern is the cable run length — probably 25-30 metres from shore power hookup to the consumer unit. Would voltage drop be an issue at that distance, or is it worth just sizing the cable up accordingly?

Also wondering about earth bonding implications when the boat's isolated from shore power but you're back-feeding into the house. Feels like it could get complicated fast from a safety/regs perspective. Has anyone actually had this signed off properly, or is everyone just winging it when the grid goes down? 😅

@RockyTinker same setup effectively — Multiplus in my shepherd's hut rather than a van, but the principle's identical. One thing worth flagging: check your AC input current limit settings in VictronConnect. During a handover from mains to battery you can get a brief dropout that'll reset some appliances. Took me an embarrassing amount of head-scratching to sort.

Also worth thinking about cable run length if you're parking the van any distance from the property — voltage drop on a long extension kills efficiency fast. I ran a proper 6mm² caravan hookup cable and it made a noticeable difference.

@CliffWill if your motorhome's got a Multiplus already, you're basically there — just need a decent transfer switch setup.

@RockyTinker great shout, I did exactly this last winter. Ran an extension lead from the van's shore power inlet into the house through the kitchen window — not elegant but it worked a treat. Key thing I'd flag is being really careful about what loads you're running simultaneously. The Multiplus 3000 is capable but you'll still want to prioritise — fridge, a few lights, phone charging, maybe a small heater. Don't go kettle and microwave at once or you'll be watching the BMS trip out. Also worth checking your Fogstar warranty terms around this kind of use just to be safe.

@RockyTinker great timing on this thread — I've been doing exactly this since last autumn. One thing worth flagging that nobody's mentioned yet: if you're running the Multiplus in inverter mode to power house circuits, make sure you've properly isolated from the grid first. The Multiplus won't do this automatically unless you've configured it correctly in VEConfigure. Had a slightly hairy moment before I sorted mine properly. Also worth checking your extension lead gauge — 3000W through undersized cable gets warm quickly. What's your typical load looking like during an outage?