Advice Needed: Switching from 3-Phase to Single-Phase Setup

Q&A and troubleshooting
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Hello everyone,

I’m currently running a 3-phase Victron setup and I’m considering switching to a single-phase configuration to better suit my household energy needs. I’d really appreciate your input on whether this change is technically feasible and what the best configuration might be.

Current system:

  • 3x Victron MultiPlus 48/5000
  • 16 kWp solar
  • 20 kWh battery storage
  • RS 450/200
  • Victron busbar with Smart BMS

This setup has been operational since late last summer. During this time, I’ve also been renovating the house—including the electrical system—and I’ll soon be installing a new distribution board. This board can be configured for either single-phase or three-phase (my grid connection is 3x20A), so I need to make a final decision soon.

The challenge:
Load balancing has proven difficult. While the base load is relatively even across the phases, high-demand scenarios—such as using the oven with light house loads, running the induction cooktop while the EV is charging, or operating the dishwasher and washing machine at the same time—frequently trigger overload warnings on one phase, while the other two remain underutilized.

I currently don’t have any 400V appliances, and while a 3-phase EV charger might be something for the future, it’s far from certain.

Over the past winter, I managed fine by grid-charging the batteries at 3A for 2–3 hours per day. At the moment, I use the “Ignore AC Input” setting, and I’ve configured the generator contact to trigger grid charging when the battery SoC drops below 15%.

Possible new configurations:

Option 1:
Parallel two MultiPlus units for general household use and dedicate the third to EV charging.

  • Peak load has reached 32A only once (for less than 10 minutes), with typical peaks around 24–26A.
  • Two units in parallel (10 kVA total) should comfortably handle normal household demand.
  • The third unit would be used exclusively for EV charging, only switching on when needed.

I’m not entirely sure if this configuration is possible or advisable with Victron hardware.

Option 2:
Use one MultiPlus most of the time, with a second in search mode to assist when needed.

  • During the night and when we’re away, household power demand is under 500W—often for 16+ hours per day.
  • One unit could handle these low loads on its own.
  • A second unit could be placed in search mode and configured (possibly via an assistant) to wake up and assist during higher loads.
  • The third unit would remain dedicated to EV charging, as in Option 1.

Questions:

  • Are either (or both) of these configurations technically possible using Victron equipment?
  • If yes, could anyone point me to documentation, configuration guides, or examples to help set this up?

Thank you very much in advance for your time and advice!

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Hi isnt it more a load spreading problem in your distribution board? Since its one phase overloading, i would stick to 3 phase, so the system can be controlled with one GX

If you split it up in 3 separate phases you will need 3 gx and 3 batterys (if you want to run it correctly)

Is 3 extra mp2 5k in 3x2 parallel an option, if the current mp2 5ks are not too old ( you would need more battery also for that)

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I didn’t realize I’d need one GX device per MultiPlus II—definitely a bummer.

Sure, adding 3 more MultiPlus units would solve the power limitations, but honestly, this system is already quite expensive. I’d much rather spend that kind of money (around €2500) on additional battery storage. Plus, let’s not forget the physical space they’d take up—something the “boss at home” strongly objects to. :sweat_smile:

As for better load distribution, I’ve been working on it slowly since September. The truth is, it’s not that easy. Ideally, I’d need to run dedicated circuits: one cable just for the oven, one for the dishwasher, etc. I already have a dedicated line for the induction cooktop. But even with that, I still end up with “forbidden combinations” of appliances. It’s hard to explain, but after months of tweaking, I can confidently say that 5 kVA is just not enough.

Take the oven—it pulls 3000W on its own, leaving very little headroom for anything else.

In winter, on sunny days, I want to charge the EV right after it gets home to make the most of direct solar input (instead of draining the batteries). That’s another 2500W out of my 4000W budget… and that often overlaps with dinner prep time. So yeah, charging the car and cooking dinner at the same time gets tricky.

And honestly, I’m getting tired of my wife having to ask me if she can start the washing machine or dishwasher. I want our energy system to be invisible—something that just works, without us having to think about it all the time.

This really is a power availability problem. Sure, 3x 15kVA inverters would fix everything :grinning_face_with_smiling_eyes: — but let’s be real, budgets aren’t unlimited.

That’s why I still believe Option 2 is the best solution for me:

  • One inverter handles the base load (which is fine 70%+ of the time),
  • A second one kicks in when needed for peaks.

Basically, I want to put all the power into one “bucket” and draw from there as needed. I could maybe even get by with just 2x MP2 units—if I exclude the car, or shift its charging to night-time (which I’d rather avoid due to the noise the MP2 makes at night).

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You could also split heavy loads to ac in side, i have that too

Our whole house is on 3phase 3k multiplus 2, with 3x25A grid
but the oven en electric cooking is on ac in side,

rest on ac out (dish washer, washing machine, dryer, microwave, qooker, airco)

I never have any issues or need to account loads, but i dont have an ev (yet) however
I did the tweaking too when setting up this system, but i do have separate lines for most appliences

See my profile for a link to my topic

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Unfortunatelly for the case, I only have AC-IN 4 months per year.
I’m disconnected from the grid since 26 February.

My goal is being off-grid.