Zero export with Growatt inverter and Shine WiLan-X2?

Been down this rabbit hole recently with my static caravan setup, so thought I'd share what I've found and see if anyone else has tackled this.

I've got a Growatt MIN series inverter and I'm trying to implement proper zero-export control — essentially preventing any backfeed to the grid whilst still managing battery charging intelligently. The Shine WiLan-X2 dongle looks promising because it exposes Modbus TCP registers, which in theory gives you programmatic control over the inverter's operating parameters.

The register map is the tricky bit. Growatt's documentation is patchy at best, and what's available online seems to vary between firmware versions. I've been cross-referencing several community-sourced register lists, but I'm not confident I've got the right ones for export limitation specifically.

A few questions for anyone who's been through this:

• Has anyone successfully written to the export power limit register (I believe it's around holding register 122/123 on some models) via Modbus TCP using the WiLan-X2 rather than the older ShineWifi-X?
• Is there a meaningful difference in latency or reliability between the WiLan-X2 and a direct RS485 connection? For genuine zero-export you need fairly fast response times.
• Has anyone integrated this with Home Assistant or Node-RED for dynamic control based on a CT clamp reading?

For context, my setup is primarily off-grid emergency backup for the caravan, but I do have a grid connection available and I'm very keen to stay on the right side of G98/G99 compliance.

Would be particularly interested to hear from anyone running Victron kit alongside Growatt — whether there are any conflicts managing the AC coupling side of things.

@FormerTeacher61 ooh yes been through exactly this with my garden office setup! 🙌

The Shine WiLan-X2 + CT clamp combo does work for zero export but the CT clamp placement is everything — needs to go on the grid side of your consumer unit, not the inverter side or you'll get mad fluctuations.

Also worth checking your Growatt settings:

• Parameter 27 — export power limit
• Parameter 29 — enable the CT function

Mine took a few attempts to stabilise. Growatt's ShinePhone app lets you monitor whether it's actually holding zero or drifting.

One gotcha with static caravan setups specifically — if your grid connection is single-phase but undersized, the response time can lag a bit. Not a dealbreaker but worth knowing!

What firmware version are you running? Some older versions had a known bug with CT response.

Has anyone actually got this working reliably on a narrowboat context — or is that a completely different kettle of fish given the, er, constantly shifting mooring locations?

I've been eyeing up zero export for my backup setup but I keep hitting the same question: if you're not grid-tied in the traditional sense but you've got shore power as a fallback, does the Growatt even behave sensibly with the CT clamp reading fluctuating all over the shop?

Basically wondering if the WiLan-X2 is doing the heavy lifting here or if the inverter firmware is actually competent enough to respond quickly to load changes. Mine currently just does what it likes, which is charming but not exactly optimal 😅

Also — is the CT clamp placement critical? I've seen people get it completely wrong and then wonder why they're exporting like mad.

SophieGraham | 📍 Yorkshire | ⚡ 6.2kW array | Posts: 847

@FormerTeacher61 great thread! I've got this running on my smallholding and it took a bit of fiddling but it's solid now.

One thing nobody's mentioned yet — make sure your CT clamp is clamped around the correct cable at your consumer unit. Sounds obvious but I had mine on the wrong conductor initially and was getting daft readings that made the zero-export logic go completely haywire.

Also worth checking your Shine WiLan-X2 firmware version. Growatt pushed an update earlier this year that improved the response latency noticeably.

@SunnyFisher narrowboat is a different beast I'd imagine — your grid connection situation will vary massively depending on marina hookup arrangements. Might be worth starting a separate thread with your specific setup details? 🙂

@SunnyFisher genuinely curious about the narrowboat angle too — my boat has been on my mind lately and I wonder if the challenge there is more about the fluctuating loads from things like the bilge pump and inverter charger constantly shifting the baseline reading?

Has anyone tested whether the CT clamp placement matters more in a marine setup given all the different DC and AC circuits potentially running alongside each other? Presumably interference could throw off the zero export calibration?

@FormerTeacher61 did you find the Shine WiLan-X2 response time quick enough to actually prevent export, or does it lag a bit before clamping down? That feels like the critical question for anyone on a tight DNO agreement.