A Victron ESS setup turns a MultiPlus-II and a battery into a grid-tied home battery. It stores extra solar, powers the house in the evening and keeps the lights on during an outage. ESS stands for Energy Storage System, Victron’s name for the operating mode. Here’s how it works and what you need, using the MultiPlus-II GX datasheet and Victron’s energy meter guide.
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.
How a Victron ESS Setup Works
Victron’s datasheet describes it this way: using an external current sensor or energy meter, the MultiPlus-II optimizes self-consumption and can prevent feeding power to the grid if you need that. It “will use excess PV power to charge the batteries or to feed power back into the grid.” It discharges the battery, or draws from the grid, to cover your loads. During a power outage, it disconnects from the grid and keeps supplying the loads on its output.
Parts List
| Part | Role |
|---|---|
| MultiPlus-II GX (or MultiPlus-II + Cerbo GX) | Inverter/ |
| Lithium battery with CAN-bus BMS | Storage, sends charge limits to the GX |
| SmartSolar MPPT and/or grid-tie PV inverter | Solar |
| Energy meter or 100A current sensor | Measures grid import and export |
Sources: MultiPlus-II GX datasheet; Energy Meters Selection Guide.
Two Solar Layouts
Victron’s datasheet shows two layouts. In grid parallel, a solar charge controller charges the battery on the DC side. In grid in-line, a PV inverter sits on the AC output. Many systems combine both.
MultiPlus-II GX Sizes
| Model | Cont. power (25°C) | Max feed-in | Battery charge |
|---|---|---|---|
| 24/3000/70-32 | 2,400W | 3,000VA | 70A |
| 48/3000/35-32 | 2,400W | 3,000VA | 35A |
| 48/5000/70-50 | 4,000W | 5,000VA | 70A |
Source: MultiPlus-II GX datasheet (230V). For US 120/240V homes, look at the MultiPlus-II 2x120V or a pair of 120V units.
Choosing the Grid Meter
- Single-phase up to 100A: ET112
- Three-phase up to 65A per phase: ET340 or EM540
- Split-phase or higher currents: VM-3P75CT, using current transformers
Commissioning Steps
- Install and wire it to the manual, and have an electrician make the panel connections.
- Connect the battery’s BMS to the GX over CAN-bus and turn on DVCC.
- Load the ESS Assistant onto the MultiPlus-II with VictronConnect or VEConfigure.
- On the GX, open Settings → ESS and pick a mode (for example, Optimized with or without BatteryLife).
- Set the grid setpoint and the feed-in limits your utility allows.
- Test a grid outage with the main breaker off.
Grid Code and Approval
Grid-tied storage needs your utility’s approval, and the inverter must be on the local grid-code list. Victron’s settings include country grid codes, but compliance is up to the installer.
Victron’s MultiPlus-II GX product page has the full datasheet and manual downloads.
Understanding the ESS Modes
On the GX device’s ESS menu, the main modes are:
- Optimized (with BatteryLife): uses the battery for self-consumption and raises the minimum state of charge automatically if the battery hasn’t reached full charge for a while. It suits lead-acid and some lithium setups.
- Optimized (without BatteryLife): uses the battery down to the minimum state of charge you set, which most lithium batteries handle well.
- Keep batteries charged: holds the battery full for backup and only discharges it during an outage.
- External control: for advanced setups where another system sends setpoints.
Pick the mode that matches your goal: lower bills, maximum backup, or a balance of both.
Worked Example: A Day With 5kW of Solar
A 230V home with a MultiPlus-II GX 48/5000, a 10kWh lithium battery and a 5kW grid-tie PV inverter on the AC output:
- Morning: the house uses 600W while the panels ramp up. The battery covers the gap, and the grid stays near zero.
- Midday: the panels produce 4kW while the house uses 1kW. The surplus 3kW charges the battery, which fills in a little over three hours from half charge (estimate: 5kWh ÷ 3kW ÷ 0.9).
- Afternoon: with the battery full and feed-in allowed, surplus solar flows to the grid up to the feed-in limit.
- Evening: the house uses 1.2kW for four hours, about 4.8kWh, and the battery supplies it (estimate).
- Night: once the battery reaches the minimum state of charge, the house draws from the grid until morning.
Worked Example: Backup During an Outage
With the battery at 70% (7kWh) when the grid fails, and essential loads on the AC output drawing 400W, the battery can carry them for roughly 15 hours before hitting a 10% reserve (estimate: 6kWh × 0.95 ÷ 0.4kW). Solar on the AC output continues to charge the battery during the day while the grid is down, using frequency shifting to control the PV inverter.
Sizing the Battery
A simple way to size the battery is to look at evening and overnight use. If your home uses about 5kWh between sunset and bedtime, a 10kWh battery covers it with room for reserve. If backup is the main goal, size for the essential loads you want to keep running and for how long.
Setting the Minimum State of Charge
- Set it at a level that leaves useful reserve for outages, such as 20–30% (example setting).
- Raise it before storm season to keep more energy for backup.
- Lower it in summer if outages are rare and you want more self-consumption.
Scheduled Charging
ESS can charge the battery from the grid at set times, for example during a cheap overnight tariff, up to a chosen state of charge. That lets the battery cover expensive evening hours even on cloudy days.
Monitoring the Results
In VRM, the consumption and solar charts show how much energy came from the battery, the panels and the grid each day. Over a month, they show how much grid use ESS has shifted.
FAQ
Does ESS work without solar?
Yes. It can still provide backup and shift grid use, though solar is where most of the savings come from.
Can I block all grid feed-in?
Yes. Victron’s datasheet says ESS can prevent grid feed.
Which ESS mode should I choose for lithium?
Many lithium installs use Optimized without BatteryLife, with a minimum state of charge suited to your backup needs. Follow your battery maker’s guidance.
Can ESS charge from the grid?
Yes. Scheduled charging lets it charge the battery from the grid at chosen times.
What loads stay on during an outage?
Only the loads wired to the MultiPlus-II’s AC output. Plan which circuits go there before installation.
Does ESS need a CAN-bus battery?
It works best with one, since the battery’s BMS shares its charge limits through DVCC. Check Victron’s battery compatibility list for your battery.
Sources: Victron MultiPlus-II GX datasheet; Energy Meters Selection Guide; Cerbo GX manual (DVCC for ESS), victronenergy.com, accessed Oct 2026.
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