🏠 Case Study: Building a Demo Home That Lives Off-Grid Without Oversizing

Why is this a Case Study, not just a Showcase?
This site was designed from the ground up to demonstrate that you don’t need a massive 8kW or 12kW inverter to live off-grid — not even in a full, modern household. With the right system design, smart automation, and energy discipline, even a 6kW inverter can deliver a 95% fully solar-powered lifestyle for a family of four.

System Overview and Goals

The home runs entirely on solar and batteries — with no grid connection active by default. Using Node-RED automation on a Victron GX, the system mimics a generator scenario:

• The grid is connected only when battery drops below 20%
• It disconnects again automatically when battery reaches 30%

This logic simulates a site where grid is treated as backup — just like a generator would be in a remote off-grid property.

Real-World Energy Performance

The house consumes around 500kWh/month — including:

• 2× 3kW geysers
• Electric oven and induction hob (no gas)
• Full scullery and standard appliances
• A 3-bedroom layout
• An electric lawnmower with a 5.5kW startup draw

Even with this load, during summer and good weather:

• A full battery at sunset typically still sits at 80% the next morning
• That’s 15 hours of use from just 20% of a 14kWh battery
• Winter is more challenging — in June, West Coast weather reduces PV dramatically, and grid support becomes necessary

Importantly, compared to competitor systems, this setup delivers notably better PV production under poor weather conditions — something we've seen firsthand.

Automation: Where Node-RED Takes Over

The true strength of this system is its automation layer — Node-RED running on the Cerbo GX, tightly integrated with Victron and Home Assistant.

1. Smart Grid Connection Logic
   Node-RED controls when the grid connects based on battery thresholds.
   Users can override this manually via:
   • The VRM portal (ESS menu toggle)
   • The Touch display
2. Overload Protection via Geyser Control
   If total load approaches or exceeds inverter limits (6kW rated, 7kW surge):
   • Node-RED will temporarily disable one or both geysers
   • This protects the inverter while keeping critical loads online
3. Thermal Storage via Secondary Geyser (Dump Load)
   A second geyser is configured in series as a dump load:
   • When the battery is full, this geyser heats using excess PV
   • At night, if the first geyser is emptied, it’s re-filled with hot water from the second one
   • This reduces or even eliminates the need for morning reheating, saving significant battery energy
4. Bonus Sensors for Demo & Display
   • A Ruuvi sensor in the kitchen displays ambient temperature
   • An EyeGas monitor shows gas bottle levels used for the braai
   • Both are visible in VRM and on the Touch 50 display, showing how easily non-energy devices can be integrated into the system

This approach combines battery storage, thermal storage, and practical automation into one cohesive system.

System Components

Victron Energy Platform:

• Inverter: Multi RS 6kW
• Battery: 1× 14.3kWh Solar MD lithium battery
• Solar: 4.6kWp PV array connected to the hybrid inverter
• Control: Cerbo GX with Touch 50

Automation & Monitoring:

• Node-RED running directly on GX for real-time control
• Cerbo GX controls Geyser 1 & 2 via Relay 1 & 2, which operate load-bearing contactors to switch the geysers
• Grid connection override available in VRM and local touchscreen
• Second geyser used for intelligent dump load and storage

Extended Automation (Home Assistant):

• Not shown here, but connected via MQTT
• Includes lights, motion sensors, CCTV, smart plugs, and energy meters
• Smart appliances like the tumble dryer are integrated via local automation
• (To be featured in a future dedicated automation showcase)

Conclusion

This house is proof that with smart design, modest hardware, and clever logic, a home can operate 95% solar-powered across a full 12-month cycle — using just a 6kW inverter.

It doesn’t just run — it runs smart.
👉 Contact us to learn how to maximize efficiency without oversizing your system