How can I see my AC coupled PV?

Been scratching my head over this one for a while now, so thought I'd open it up for discussion.

Running a Multiplus II with AC-coupled PV (Fronius on the AC output side) alongside a Pylontech battery bank out in my garden office setup. The batteries, grid input, Multiplus itself — all showing up nicely in VRM and on the Cerbo GX. No complaints there.

The problem is the AC-coupled solar generation figures. They're either missing entirely or wildly inaccurate depending on the day. I know the Fronius should talk to the Cerbo via Modbus TCP, and I've got that configured, but something clearly isn't right. The PV yield just doesn't reflect what I'd expect given the irradiance we've had this week.

A few questions for the group:

• Is anyone else running a Fronius + Multiplus II combo and getting clean data through to VRM?
• Does the ET112 energy meter on the AC input actually help here, or is that solving a different problem?
• Would a Victron SmartShunt anywhere in the chain add anything useful, or is that beside the point for AC-coupled monitoring?

I've read through the Victron integration guide and the Fronius Modbus docs until my eyes glazed over. The IP address is static, the port is correct, and VRM still shows gaps.

Feels like there's a settings rabbit hole I'm missing. If anyone's cracked this — particularly in a UK install where you might also be on the grid occasionally — I'd love to know what finally made it click. What does your monitoring setup actually look like?

@IslandExplorer — classic Victron visibility gap, this one.

The AC-coupled PV won't show in VRM or the CCGX/Cerbo as "PV power" unless you've got the Fronius properly integrated. Make sure it's on the same local network as your GX device and that Fronius Solar API is enabled on the inverter itself — it's off by default on some firmware versions.

Once the GX discovers it automatically, the power flow diagram starts making proper sense. You'll see AC-in, AC-out, battery, and the Fronius contribution all laid out.

Worth checking your VEConfigure settings too — the AC input current limits can sometimes mask what's actually happening in the logs.

Had a similar head-scratch moment with my own setup before I realised the Fronius just needed pointing at the right subnet.

@IslandExplorer worth being precise here — the Fronius needs to be connected to your Cerbo via Ethernet or WiFi, and you must enable the SunSpec Modbus TCP on the Fronius itself. Easy to miss that step.

Once that's done, the Cerbo picks it up automatically and VRM shows it properly under "AC-coupled PV" — separate from any DC-coupled sources, which matters for your energy balance figures.

On my own tiny cabin setup I've got a Fronius Primo doing exactly this. Took me an embarrassing amount of time to realise the SunSpec setting was off by default on my unit.

Also double-check your Fronius firmware is reasonably current — older versions had Modbus bugs that caused intermittent dropouts in VRM.

@IslandExplorer the key thing nobody's mentioned yet is that once your Fronius is properly talking to the Cerbo via the Solar API (not just network-visible), you'll see it show up under Settings → Fronius on the Cerbo, and from there it populates the AC-PV field in VRM correctly.

Worth checking the Fronius is running a compatible firmware version — older units sometimes need updating before the Sunspec/Solar API handshake works reliably. Had this exact issue with my garden office setup; the Cerbo could ping the Fronius but the yield data stayed stubbornly absent in VRM until I updated the Fronius firmware via Fronius Solar.web.

Also confirm you've set the correct device role on the Fronius itself — it needs to be configured as "AC-coupled on output" rather than grid-tie, otherwise the frequency-shift 1:1 rule won't apply correctly either.

Great thread — just to add something practical on top of what @PeakExplorer and @BaySeeker have touched on: once everything's communicating properly, do check your VRM dashboard tile layout. The AC-coupled PV will appear as a separate source from your DC-side generation, so if you've got a custom dashboard you may need to manually add the PV inverter tile — it won't necessarily appear automatically even when the data's flowing through correctly.

Also worth double-checking that your Fronius has Sunspec enabled in its settings (under the Modbus TCP configuration). Without that active, the Cerbo can see the inverter on the network but won't pull the generation data properly. Caught me out for about a week before I spotted it!