A Victron MultiPlus well pump setup depends mostly on one detail: whether your pump runs on 120V or 240V. Most deep-well pumps in US homes are 240V, and that changes which Victron units can run them during an outage. Here’s how to work it out using Victron’s datasheets and manuals.
Electrical work can be dangerous: follow the manual, fuse and size every cable correctly, and use a licensed electrician for anything connected to household wiring.
Step 1: Read the Pump Nameplate
Check the voltage, horsepower and running amps on the pump or its control box. Starting current for a submersible pump can be several times its running current.
The 240V Catch
Victron’s MultiPlus-II 2x120V passes 120/240V through from shore or grid. On battery, its manual states the output is always 120V in inverter mode. The Quattro-II 2x120V works the same way. So neither runs a 240V well pump during an outage.
To run a 240V pump on battery, use two 120V MultiPlus-II or Quattro units configured for split phase, which Victron supports.
Victron MultiPlus Well Pump Sizing
| Setup | Continuous at 25°C | Peak | Runs 240V on battery? |
|---|---|---|---|
| 1 x MultiPlus-II 48/3000 | 2,400W | 5,500W | No (120V only) |
| 1 x MultiPlus-II 2x120V 3000 | 2,400W | 5,500W | No (120V in inverter mode) |
| 2 x MultiPlus-II 48/5000 split phase | 8,000W | 18,000W | Yes |
Sources: Victron MultiPlus-II 120V and 2x120V datasheets and manual. Split-phase figures are two units added together.
Surge Example (Estimate)
A 1HP 240V pump running at about 10A (2,400W) might pull 3–5 times that for under a second at startup. Two 48/5000s give 9,000W peak per leg, which covers most 1HP pumps. A soft starter or a variable-speed pump drive lowers inrush further.
Example figures. Check your pump’s locked-rotor amps.
A 120V Pump Is Easier
Shallow-well and jet pumps are often 120V. A single MultiPlus-II 48/3000 (5,500W peak) usually runs a 3/4HP 120V pump.
Energy Use Is Small
Pumps run in short bursts. If yours runs 1 hour a day at 2,400W, that’s about 2.4kWh, roughly a quarter of a 10kWh 48V bank. The inverters’ own idle draw matters too: a MultiPlus-II 48/5000 draws 15W at zero load, or 3W in search mode.
Tips
- Search mode can cause problems. A pressure switch closing has to wake the inverter. Test it, or leave search mode off.
- Set the generator input limit and use PowerAssist so a small generator can help with starts.
For the complete spec sheet and current manual, see the Victron MultiPlus-II page.
Worked Example: A 120V Jet Pump on One MultiPlus-II
A 3/4HP 120V shallow-well jet pump with a nameplate of about 10A running (≈ 1,200W) and an estimated start of 3–5 times that for a moment (3,600–6,000W, estimate). The MultiPlus-II 48/3000’s 5,500W peak covers the lower end of that range; a pump at the top end may need a soft starter. Once running, 1,200W sits well inside the 2,400W continuous rating, leaving about 1,200W for a fridge, lights and other essentials during an outage.
Worked Example: A Daily Water Budget
A household using 300 gallons a day from a pump that delivers about 10 gallons per minute runs the pump for about 30 minutes daily (estimate).
| Pump | Running watts (est.) | Minutes/day | Wh/day (est.) |
|---|---|---|---|
| 1/2HP 120V jet pump | 900W | 30 | 450 |
| 1HP 240V submersible | 2,400W | 30 | 1,200 |
| 1.5HP 240V submersible | 3,000W | 30 | 1,500 |
Estimates from typical pump ratings; add roughly 10% for inverter losses. Even the largest example uses only about 15% of a 10kWh battery bank per day, so the pump is rarely what limits outage runtime. Starting surge sizes the inverters; energy use sizes the battery.
Worked Example: Two 48/5000s in Split Phase
Two MultiPlus-II 48/5000 120V units configured as split phase give 120/240V on battery. Combined continuous output is about 8,000W at 25°C, so a 1HP 240V pump at 2,400W running leaves around 5,600W for the rest of the home’s backed-up loads (estimate). Victron’s VE.Bus Quick Configure Setup handles the split-phase configuration.
Soft Starters and Variable-Speed Drives
A soft starter ramps the pump motor up gradually, cutting the inrush current. A variable-speed (constant-pressure) pump drive goes further: the motor starts slowly and runs only as fast as demand requires. Either can let a smaller inverter system run a pump that would otherwise need more peak capacity. Check with the pump maker that the device suits your pump and control box.
Wiring the Pump to a Backup Panel
The usual approach is a critical-loads sub-panel fed by the MultiPlus-II output, with the well pump breaker moved to that panel. The inverter-charger then powers the pump from the battery during an outage and passes grid power through the rest of the time. A licensed electrician should design the panel layout, transfer arrangement and neutral-ground bonding.
Testing Before You Rely on It
- With grid power connected, confirm the pump runs normally through the MultiPlus-II.
- Switch off the grid input and run a tap until the pressure switch calls the pump.
- Watch the inverter’s load in VictronConnect or on a GX device at start-up.
- Repeat with your other backed-up loads running to confirm there’s enough headroom.
Battery Bank Size for a Pump System
Victron’s MultiPlus-II manuals list a recommended minimum battery capacity for each model, because the battery must deliver the high current of a pump start. On a 48V system, current is a quarter of what it would be at 12V for the same power, so a 48V bank handles a 6,000W start at roughly 140A (estimate: 6,000W ÷ 48V ÷ 0.9). Check that the battery’s maximum discharge current covers the inverters’ peak draw.
FAQ
Can I use a step-up transformer?
Victron sells an autotransformer for some setups. Have a licensed electrician design it.
Is 12V workable?
For a small 120V pump, yes. For a 240V pump, use a 48V split-phase system.
Does the well pump need its own breaker?
Yes. Follow your local code and the pump maker’s instructions.
Will a MultiPlus-II start a pump with a pressure tank?
Yes, if the inverter’s peak rating covers the pump’s starting current. The pressure tank also means the pump starts less often.
Can a generator help start the pump?
Yes. With PowerAssist, a generator and the battery share the load, which helps during starts.
Sources: Victron MultiPlus-II 120V datasheet; MultiPlus-II 2x120V manual; Quattro-II 2x120V product page (victronenergy.com, accessed Oct 2026).
Related: EcoFlow Delta 3 Max Sump Pump, Heater and AC, EcoFlow Delta 3 Max Homestead Uses, EcoFlow Delta 3 Max Home Backup, plus the Victron Energy Guide