Home Assistant and a Victron battery: what works?

A Victron battery works well with Home Assistant and Node-RED for dashboards, alerts and simple steering, such as charging the car or heating water on surplus. It gets fragile when your own flow takes over the charging and discharging of the battery. Most of what people build themselves is already in the energy management system of the Victron system: the free VRM app, alerts, and control packages from simple peak and off-peak charging to Dynamic ESS on quarter-hour prices. Use Home Assistant on top of a home battery that runs safely on its own.

You have a large house with solar panels, a heat pump, an electric car and a Victron battery. Home Assistant already runs your lights, blinds and heating. So the battery should join in: one dashboard, the car on surplus, the boiler on sun, and a monthly peak that stays low. Forums are full of people who did it. They also write how it went: "vooral een dure hobby" (mostly an expensive hobby), "it took a year to figure out", and about the link to the battery: "de brug naar de batterij was klote" (the bridge to the battery was the hard part).

The real risk is not the dashboard. It is handing the battery, and with it your back-up, to a flow on a small computer that nobody else understands. When the Home Assistant server hangs, when an update renames a sensor, or when you are away and the grid fails, the house depends on code that Victron does not support and no installer has seen.

A home owner in Kapellen works in the sector and wanted the latest technology. The system sends an alarm to his phone when the battery is full, charges from the grid when that makes sense and shows full, clear data. That is 5 kVA and 15.4 kWh, all with the standard Victron tools.

How can Home Assistant connect to a Victron battery?

In four ways, and only two of them can control the battery. Which one you use decides whether Home Assistant reads, steers, or needs the internet.

For a home battery with a GX device, the Victron GX integration is the obvious choice. It was introduced in Home Assistant 2026.5, works over MQTT on your own network and can be found automatically. On the GX device you enable MQTT access; the manual says it "only needs to be enabled when integrating a third party device or service like Home Assistant".

The integration can do more than read. Among its controls are the ESS mode, the grid setpoint for ESS, the charge current limits, the inverter mode and switches for generator auto-start. That is powerful, and exactly why the rest of this article matters.

What is Venus OS, and what does Venus OS Large with Node-RED add?

Venus OS is the software on every Victron GX device. Venus OS Large is an extended build that adds Node-RED and Signal K.

Node-RED is a visual tool: you draw flows with blocks instead of writing code. On a GX device with Venus OS Large it runs inside the system itself, so a flow keeps running even when your Home Assistant server is off. Victron publishes its own Node-RED nodes, and even calls Dynamic ESS a ready-to-use example.

Three limits to know before you switch the image type to "Large":

• Support: the GX manual says the extra features "are not officially supported by Victron Energy. Use is at your own discretion." Victron adds that it "does not provide support for systems which make use of these extended features to implement advanced solutions".
• Hardware: the Color Control GX cannot run Venus OS Large. On the Venus GX, the slowest GX device still supported, running Signal K and Node-RED together "will very likely overload the device". If a GX device runs out of memory or CPU, it reboots.
• Raspberry Pi: Venus OS also runs on a Raspberry Pi, but Victron calls that image "a community effort" and asks not to contact its service department about it.

Home Assistant or Node-RED: where should the logic live?

Safety and back-up in the Victron settings, convenience in Home Assistant, and Node-RED on the GX only for what must keep running without the server.

Our home battery page describes the GX device the same way: unlimited control, from adjusting the system to starting a back-up generator automatically. Those are system functions. A home automation server adds comfort on top. The same rule holds for Loxone or KNX, as explained in what happens to your smart home in a power cut.

What works well with a Victron battery and Home Assistant?

Everything that reads, and everything that switches other devices on or off around the battery.

• One dashboard for the house: battery, solar, grid and consumption next to the heating and the lights, without an extra app.
• Local data, also without internet: the GX integration works over your own network. One home owner set up Home Assistant precisely so he can still check the state of charge over WiFi when the internet is down.
• Surplus to the car or the boiler: Home Assistant switches the charger, a heat-pump boiler or a smart plug when the battery is full and the panels still produce. Our article on charging an electric car with a home battery explains why the car belongs on the grid side.
• Alerts that you choose: battery full, battery low, grid lost, generator running. The VRM app already has a low-battery alert; Home Assistant adds your own.
• Watching the monthly peak: a live view of the running quarter-hour helps you move loads. How the capacity tariff works for a home is in our article on the capacity tariff with a home battery.

What does not work, or breaks later?

Taking over the charging and discharging yourself. That is where the forum threads get long.

Victron describes three ESS modes. Mode 1 runs on its own. Mode 2 lets an outside system adjust settings such as the grid setpoint. Mode 3 hands the inverter over completely: you set how much power it takes from or feeds into the grid, and you write your own control loop. Victron warns that it "does not offer support" to customers or end users who build on this, "except in real specific situations".

Other things that go wrong in practice:

• Two controllers fighting: a Dynamic ESS schedule and your own flow both steer the same battery. One owner had to switch ESS off during the day with Node-RED to get his batteries filled.
• Updates: an update of Home Assistant, of an integration or of Venus OS can rename sensors or change behaviour. Test after every update, and do not update just before a holiday.
• Safety comes first anyway: Victron notes that setpoints "will be overridden by battery safety mechanisms". Your flow can ask; the battery management decides.
• The GX device under load: heavy flows on a small GX device can make it reboot, and during a reboot you have no monitoring.

Is your back-up at risk when you tinker?

Not if the back-up stays a function of the inverter itself. Yes, if it depends on a flow.

On a Victron system with back-up, the inverter takes over the connected circuits within 20 milliseconds when the grid fails. That happens in the inverter, without Home Assistant, without Node-RED and without internet. Keep it that way: no flow should switch the inverter off, change the minimum state of charge for back-up, or block the generator start. The levels of back-up and what they cover are explained in our guide to a home battery with backup power.

For long outages the generator is the safety net, and its start belongs on the GX relay, not in a script. How a generator recharges a home battery in a power cut of several days is in our generator article.

How do you keep the connection secure?

Open as little as possible, protect it with a password, and give write access only where you really steer.

• Security profile: GX devices shipped with Venus OS v3.50 or later default to "Secured". The device password must be at least 8 characters.
• MQTT access and Modbus TCP are off by default. Switch on only the one your integration needs.
• Read-only Modbus: Modbus TCP has an access setting for read-only or write. For a dashboard, read-only is enough.
• Keep it on your own network: do not open the GX device or Home Assistant to the internet with port forwarding. Remote access runs through VRM.

Who can reach your inverter from outside, and what to ask about remote access and portal accounts, is covered in our article on inverter and battery cyber security. It is written for companies, but the questions are the same at home.

Build it yourself or use the standard control packages?

Build it yourself if you enjoy it and accept that you maintain it. Use the standard packages if the battery simply has to earn and protect.

Our software page describes three packages for exactly these needs: Dynamic Control for users who set their own rules, a peak and off-peak programme, and Dynamic ESS, which uses quarter-hour prices and weather forecasts. Home Assistant then does what it does best: the rest of the house. Whether Dynamic ESS pays off on your contract is in Victron Dynamic ESS on a home battery.

What should you ask before connecting Home Assistant to your battery?

Five questions, for yourself and for your installer.

How do we set up monitoring and control on our home batteries?

We measure first, build the back-up in the system itself, and give you full insight through the Victron tools.

Take a look at the projects in Kapellen and Hasselt.

1. Step 1: We measure your consumption before we size anything, so the battery and the panels fit what the house really uses.
2. Step 2: We decide with you what must keep running in a power cut, and build that into the inverter and the switchboard.
3. Step 3: The GX device controls the system: settings, alerts and, where there is one, the automatic start of a back-up generator.
4. Step 4: You follow everything in real time in the free VRM app and portal, per phase and per minute, hour or day, locally or from anywhere.

Our team includes three certified battery experts, and we also maintain and repair existing battery systems. Want to see which control fits your house? Read more about our energy management software.