Local-only Marstek Venus E Battery Integration with Home Assistant
Published: 2026-01-11, Revised: 2026-01-16
TL;DR Integrating a cheap (~1050€) 5kWh AC-coupled battery into an existing 30kWp PV system. The goal: Zero-cloud dependency, full local control via Modbus TCP, and a "Zero Export" regulation loop using Home Assistant. This post covers the physical installation using a standard TV mount, RS485 wiring, and the complete software logic.
In 2020, I took the initiative to install a 30kWp PV system on my own. Over the last 4 years, I achieved a self-consumption rate of roughly 48-50%.
See my PV production 2021-2025
With the price of the Marstek Venus E 2.0 dropping to around €1.049 in August 2025, I saw an opportunity to increase self-consumption to around 78%. The Marstek's size ( 5.12 kWh ) was ideal for my consumption pattern, enabling me to maximise the number of use cycles. The return on investment (ROI) calculation was promising enough to justify the experiment. Note that my current electricity price is at €0.32/kWh and I sell my electricity at €0.082/kWh (fixed for the next 15 years). According to these figures, I should recoup my investment in about six years. After that, I estimate savings of around €250 per year.
See my ROI calculation for the battery
I wanted to avoid the manufacturer's cloud and app entirely.
Privacy/Security: I don't want any IoT devices from Chinese vendors active on my main Ethernet network (no offence, Marstek!). Control: I want granular control over charging/discharging logic based on my specific grid meter readings, not a black-box algorithm. Robustness: The system should work regardless of internet connectivity. Local access also ensures that I can still use the battery if the vendor goes bankrupt or discontinues its service (local access ability was actually my main criteria for chosing the Marstek product).
Hardware Installation#
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