Zusammenspiel Solarspitzengesetz (60%) und Systemeinspeisung begrenzen für nicht Victron AC-Inverter

Interesting topic this one, and something I've been wrestling with in my own setup.

For context: I'm running a van conversion that doubles as an emergency backup system at home, so I've got a slightly unusual hybrid arrangement. My panel array sits at around 6kWp, and whilst the UK's G98/G99 export limiting requirements aren't identical to the German 70% rule, the underlying engineering challenge is very similar — how do you enforce a hard export cap when your inverter isn't a Victron unit with native ESS integration?

My non-Victron inverter (a Deye hybrid) doesn't talk to the Cerbo GX natively, which makes coordinated curtailment a right headache. A few approaches I've been researching:

• CT clamp feedback loops — measuring grid export and throttling the inverter via its RS485 port
• External relay-based curtailment using a Raspberry Pi watching a Shelly EM
• DNO-approved export limiters (Powerelectronics, Solar Edge, etc.) fitted at the meter — expensive but clean

The fundamental problem is that when battery SOC hits 100%, all that surplus has to go somewhere, and if your inverter isn't responding fast enough to the curtailment signal, you'll spike above your limit before it catches up.

Has anyone here successfully implemented dynamic export limiting on a non-Victron inverter in a UK residential-adjacent setup? Particularly curious whether anyone's used Modbus TCP bridging to get a Deye or Growatt talking to a Venus OS device properly.

Would be good to get a proper thread going on this — feels like it comes up constantly but there's no definitive UK-focused guide anywhere.

@PartnerAdventure really curious about your dual-use setup there — van and home backup is exactly the kind of thing I've been pondering for my own conversion.

Quick question though: when you say the 60% feed-in cap is affecting your system, are you hitting that limit frequently enough that it's actually causing meaningful battery wastage, or is it more of a theoretical concern at this point?

I ask because on my boat I was convinced I needed to solve for peak solar scenarios, but in practice the UK's cloud cover means I'm rarely at genuine MPPT saturation anyway!

Also — are you using any non-Victron inverter specifically for cost reasons, or is there a technical reason it fits your setup better? Wondering whether something like a Fogstar-compatible Victron Multiplus wouldn't just resolve the feed-in limiting issue natively.

@PartnerAdventure the 70% rule (it's 70% in most UK DNO agreements, not 60% — worth double-checking your G98/G99 paperwork) is honestly a pain when you're mixing inverter brands.

Main issue I've found: non-Victron inverters don't play nicely with external power limiters. Victron's ESS assistant handles the feed-in cap natively, but if you're using something like a Growatt or Deye you're essentially relying on the inverter's own built-in limiter — which varies massively in accuracy.

A CT clamp on the grid feed point is your friend here regardless. Keeps the DNO happy and gives you actual data rather than guessing.

What inverter are you running specifically? That'd narrow it down considerably — some have solid zero-export modes, others are genuinely hopeless.

@EmmaEdwards82 good shout on the G98/G99 distinction — that trips people up constantly.

On the non-Victron inverter question though, this is where it gets fiddly. Without a Victron GX device in the loop you're essentially doing export limiting "manually" or relying on whatever the inverter's own firmware offers. Some of the cheaper units have absolutely no way to communicate with a meter or CT clamp.

Had a similar headache before I went all-in on Victron kit. The MPPT + Cerbo GX combo handles it elegantly, but that's obviously a cost commitment.

For a non-Victron route — worth looking at whether your inverter supports Modbus TCP or SunSpec. Some third-party solutions like Node-RED setups with a proper CT clamp can bodge together export limiting, but reliability varies wildly.

What inverter are you actually running @PartnerAdventure?

@EmmaEdwards82 and @RetiredEngineer86 have covered the G98/G99 point well so I won't rehash that.

What I'd add specifically on the non-Victron AC-coupled limitation question: without a Victron at the heart of the system, you lose the frequency-shift curtailment mechanism (the "Frequency Shift Power Control" that Victron uses to throttle a compliant solar inverter via grid frequency manipulation). Most non-Victron inverters won't respond to that signal at all.

Your practical options without that ecosystem are:

• External export limitation relay — some DNOs accept this
• CT clamp-based export limiter on the inverter's AC output
• Inverter's own built-in export limiter if it has one (SMA Sunny Boy handles this reasonably well for example)

In my shepherd's hut setup I actually went full Victron partly because I didn't want to bodge this particular problem. The ecosystem cost is real but the integration is genuinely clean.