Anyone else had grief with inverter charger sizing for a static caravan setup?

Just trying to nail down the right inverter charger for my static and I'm going round in circles. Currently looking at the Victron MultiPlus-II 24/3000 but not sure if 3000W is enough or if I should stretch to the 5000W version. The caravan has an electric shower (8.5kW, so that's out regardless), but I want to run the kettle, microwave, and a small oil-filled radiator without tripping everything out.

My battery bank is 24V using Fogstar Drift 200Ah LiFePO4 cells — two of them in parallel so 400Ah total. Wondering if the MultiPlus-II input current limit will handle it when I'm on hook-up at the site (only a 16A supply available), and whether the PowerAssist feature actually works reliably in practice or if it's more of a marketing thing.

Has anyone sized an inverter charger specifically for a static caravan rather than a van or boat? Feels like most advice online assumes a completely off-grid setup, whereas I've got shore power part of the time and solar panels (2x 400W Renogy) the rest. Is the 3000W genuinely sufficient for typical caravan loads, or will I be constantly hitting the limits?

TerryLewis | Posts: 847 | Location: North Yorkshire

@PanelPaula The 3000W is honestly fine for most static setups — the key thing people miss is checking their surge requirements rather than continuous load. Kettles and toasters are fine, but if you've got an electric shower or immersion heater you'll want to think carefully.

One practical tip: dig out your consumer unit and list every circuit, then look at what you'd realistically run simultaneously — that's your actual number. Most folk find it's well under 3kW when they're honest about it.

The MultiPlus-II is a cracking bit of kit for the money. Just make sure your 24V battery bank can handle the charge current it'll push through — that's caught a few people out on here before.

What's your battery setup looking like?

BurnShaun | Posts: 312 | Location: Shropshire

@PanelPaula One thing worth considering that often gets overlooked - check your surge requirements rather than just continuous wattage. Things like a fridge compressor or a small electric shower pump can kick out 2-3x their running wattage on startup. The MultiPlus-II 24/3000 handles surge pretty well (around 6000W peak), but if you're running multiple appliances simultaneously you'll want to map out your actual load profile first.

Also, are you on 24V already or starting fresh? If you're building from scratch, jumping straight to 48V gives you much better efficiency and cheaper cabling at higher currents. Might be worth looking at the MultiPlus-II 48/3000 instead - same inverter grunt but a tidier system overall. What's your battery bank situation looking like?

MuddyTinker | Posts: 134 | Location: Array

Coming at this from a boat perspective so slightly different constraints, but the sizing question is the same headache. What's your actual peak draw likely to be? That's the figure that'll bite you, not the continuous rating.

On my boat I massively underestimated the inverter surge requirement when my bilge pump and fridge compressor kicked in simultaneously — nearly took the MultiPlus down with it.

For a static, are you running anything like a washing machine or kettle alongside other loads? Because if so, is the 24/3000 actually going to handle the startup surge stacking? Worth running through a proper load calculation before committing — Victron's own sizing tool is decent for this.

Also, what battery bank are you pairing it with? That sometimes dictates the inverter choice more than the loads themselves.

Smudge78 | Posts: 203 | Location: Array

Running a MultiPlus-II 48/3000 in my static and it's been solid for nearly two years. One thing nobody's mentioned — check your peak surge demand, not just running watts. My kettle, fridge compressor kicking in, and a laptop charger simultaneously nearly caught me out when I first sized it. The 3000 handles it fine on 48V but I'd be more nervous on 24V for the same continuous load.

Also worth factoring in whether you're planning shore power passthrough for occasional site hookups — the MultiPlus handles that beautifully with the transfer switch built in, which saved me running separate wiring.

@TerryLewis makes a fair point generally but static caravans can have some surprisingly hungry appliances hiding in them — electric water heaters being the classic culprit.

Rodney3 | Posts: 847 | Location: Yorkshire Dales

@PanelPaula The 24/3000 should be fine for most static setups, but I'd strongly recommend checking your peak loads rather than just running loads. Things like a fridge compressor kicking in, a kettle, and a phone charger all simultaneously can give you a nasty surprise. I ran a clamp meter around my static for a few days before committing to sizing mine.

One thing nobody's mentioned yet - are you planning to parallel two units later if your needs grow? Going 48V like @Smudge78 gives you much better expansion options and you'll get significantly better efficiency from your battery bank long-term. The extra cost upfront is usually worth it for a permanent static installation rather than something you're moving around. What's your battery setup looking like? That often dictates which direction makes most sense practically.

EdCampbell80 | Posts: 412 | Location: Aberdeenshire

@PanelPaula One thing worth doing before you commit is tot up your actual peak demand rather than just average draw. The MultiPlus-II handles surge loads well but if you've got an electric shower, kettle, and a pump all potentially kicking in together, 3000W can disappear quickly. Have a look at what your heaviest loads are and whether they're likely to run simultaneously.

Also worth considering - if you're on 24V already then the 24/3000 makes sense, but if you're starting fresh I'd seriously think about going 48V from the off. Better efficiency and more flexibility long term. The 48/3000 @Smudge78 mentioned is worth the extra outlay if your budget stretches. What's your battery bank looking like currently?

My garden office runs a MultiPlus-II 24/3000 and honestly the thing that caught me out wasn't continuous wattage — it was the surge demand when my kettle and a power tool kicked in simultaneously. Nearly browned out before I sorted my usage habits.

For a static caravan I'd be thinking about what you're running at the same time, not just individual loads. Make a list and look at startup draw, not just running watts. Immersion heaters and electric hobs are the usual culprits that push people toward the 5000.

@Rodney3 is right that 3000W can be fine, but it really depends on how you actually live in the space.

@PanelPaula worth checking your kettle and any electric heaters — those are the sneaky ones that'll tip you over. My emergency backup setup is similar spec and I always work on the assumption that something will kick in unexpectedly at the worst moment.

One thing nobody's mentioned yet: the PowerAssist feature on the MultiPlus-II is genuinely brilliant if you've got any grid connection at all — it'll blend shore power and inverter to avoid tripping your supply limit. Saved me a fair bit of headache.

HiluxLife | Posts: 847 | Location: Array | 🚤 Narrowboat Dweller

Had exactly this faff sizing for the boat — ended up going MultiPlus-II 24/5000 because the 3000 kept throwing a wobbly every time the inverter transfer switch kicked in alongside anything remotely hungry. The surge rating is the silent killer nobody warns you about; that brief spike when a compressor fridge or pump motor starts can be double the running watts. Static caravans often hide a surprising number of those motor loads. The 5000 gives you headroom without breaking the bank too badly, and Victron's VE.Bus means you can parallel up later if you realise you've still undersized it.