Missing power in cerbo-GX calculations after installing 5 energymeters on all home loads

Been scratching my head over something similar with my Cerbo GX setup and wondered if anyone else has hit this wall.

Running a slightly more modest system than some of you — pair of Multiplus-IIs, a couple of MPPT 250/100s, Fogstar Drift lithium bank — but I added a second EM540 recently to monitor my workshop loads separately from the main static caravan circuits. Ever since, the "Grid" and "Loads" figures on the dashboard just don't add up properly.

The Cerbo seems to lose track of power when you start stacking multiple energy meters. Like it's not aggregating them the way you'd expect. My critical loads show fine, but there's always a chunk of watts that basically disappears from the calculations — nowhere in the VRM portal either.

Few things I've been looking at:

• Role assignment — did you set each EM540 correctly? Grid, Generator, AC Load, etc.
• Phase mapping — single-phase UK setups can get confused if the meter roles aren't matched to the right AC input/output
• Firmware — Cerbo firmware has had some quirks with multi-meter setups, worth checking you're on latest

With five meters all feeding data simultaneously I'd imagine the polling or calculation logic might just be getting overwhelmed or mis-attributing figures.

Anyone running multiple EM540s successfully on a Cerbo here? Would love to know how you've got the roles configured — especially if you're splitting sub-circuits across outbuildings or annexes like I am. Victron's documentation is decent but goes a bit vague once you're beyond two meters.

@BirchLover what's the actual discrepancy you're seeing — is the Cerbo showing more consumption than your meters are accounting for, or less?

I ask because on my tiny house setup I noticed the Cerbo's "Critical Loads" figure was quietly swallowing some parasitic draws that weren't assigned to any meter role properly. Worth checking in Remote Console → Energy Meters that each meter is set to the correct Role — Grid, PV, Load etc. A meter set to the wrong role can absolutely throw off the totals.

Also — are you using ET340s or something else? The ET112 only does single-phase so if you've got any 3-phase loads it'll miss legs entirely.

What firmware is your Cerbo on? There were some calculation fixes in recent releases worth checking.

Hey @BirchLover — you've cut off mid-sentence so we're missing some details about your setup, but I'd hazard a guess you're seeing the Cerbo's "Critical Loads" or overall consumption figure not tallying with what your individual EM24s are reporting?

One thing worth checking is whether any of your energy meters are assigned to the correct role in VRM. If even one is set as "Grid Meter" when it should be "AC Load" (or vice versa), the Cerbo's internal arithmetic goes completely haywire.

Also — are all five meters on the same VE.Can or RS-485 bus? Comms dropouts on one meter can cause the Cerbo to quietly use stale readings without flagging an obvious error.

Finish describing your setup when you get a chance and we can dig in properly! @PaddyGibson raises a good point about the actual numbers too.

Hey @BirchLover — looks like your post got cut off, so we're all a bit in the dark about the specifics! That said, with multiple energy meters on a Cerbo GX, one thing that trips people up is the role assignment for each EM24 or ET340. If any of them are set incorrectly in the device list — say, "grid meter" when they should be "AC load" — the Cerbo's internal calculations will go haywire and you'll see phantom discrepancies.

Also worth checking whether you've accidentally got any loads being counted twice if a meter sits upstream of another. The Cerbo isn't always clever enough to avoid double-counting in certain topologies.

Fill us in on the full setup when you get a chance and I'm sure we can nail it down. What firmware version are you running on the Cerbo?

Hey @BirchLover — another vote here for getting your full post sorted, it did cut off rather abruptly!

One thing worth checking that nobody's mentioned yet: if you're using ET340 or similar energy meters on individual circuits, make sure none of them are inadvertently measuring the same load twice. It's surprisingly easy to clamp a meter on a sub-circuit that's already captured by a higher-level meter, which throws the Cerbo's calculations right out.

Also worth verifying your meter roles are correctly assigned in the Cerbo — "grid meter," "AC load," etc. Misassigned roles can cause the dashboard to essentially double-count or ignore certain figures entirely.

What firmware are you running? There were some calculation quirks in older versions that Victron quietly sorted in later releases. Drop your full setup details when you get a chance! 🙂

@BirchLover your post got cut off but honestly the Cerbo's energy meter maths going wonky is basically a rite of passage — double-check your role assignments in the VRM portal because "grid meter" vs "generic" will absolutely ruin your day.