Mains power consumption with solar and battery

My home is 3 phase installation with a 10kW solar (maxes out at about 7.4kWh due to inverter sizing and grid voltages) and a Tesla Powerwall 2 connected. I’m also part of the Simpy Energy Virtual Power Plant scheme.

I’ve just finished wiring up the IoTaWatt unit a few days ago. I haven’t connected all my CTs yet due to switchboard space and cable extensions needed. I have got 3 CTs on my consumer mains though - before the meter, after the meter isolator - with reference VTs for each phase. I’ve noticed something interesting in my phase power consumptions:

When I have net output of zero to the grid, one of the phases seems to account for the feed in for the other two phases - I can only assume this is to do with “balancing” the phases?

Once the battery is full up and we start exporting to the grid, they all go negative and match what the Tesla app and my solar analytics say (give or take a few hundred Watts):

Has anyone else got a similar set up to mine? Wondering if this is the norm. It’ll be interesting to see what happens when I finally get around to putting a CT on the battery line and a few other circuits.

FWIW - very happy with product so far. Have integrated it into Home Assistant via the REST sensor available on the Home Assistant forums and also pushing data to the InfluxDB running on HA for ease of Grafana graphs.

Very interesting. I’m going to make some assumptions based on what I see here:

The solar inverter is three-phase.
The battery is single phase and feeds into RdPh.
The battery controller has CTs on all three mains phases.

It looks like the battery system will import and export on RdPh to achieve net-zero. I an see that in the status numbers when the inverter exporting on WhPh and BlPh and throughout the daylight hours. But more interesting is what happened at about 21:30. It looks like a large 3.5kW load was introduced on BlPh, and the battery reacted by exporting on RdPh to try to compensate and stay net-zero, but it looks like it can only produce about 2.5Kw so the net went briefly to 1kW until the load dropped below 2.5kW.

CTs on all three inverter outputs and the battery would tell the whole story. You would be able to define outputs to show the load on each phase as well.

Just chipping in here - in Australia as well.

I have 2 x IOTAwatt (2nd one being setup as we speak)

The Powerwall 2 is a single phase battery system - however as Overeasy has said the energy monitor that is supplied with it is 3 phase - so it can see the total draw of your house from the grid.

I assume that you have it in Self Consumption mode which means it will try and use the battery and solar to balance out the draw from the Grid to net zero (until you hit the reserve).

Your system is complicated a bit further by the fact your are in a VPP so they actually have control of your powerwall and can force it to charge and discharge from the grid.

Assuming your solar setup is farily new you will also have to have given SAPN remote access to the inverter so that they can shut it down and/or de-rate it as required.

You have a much higher voltage on your Blue phase - than the red - it may be worthwhile getting a sparky to move the powerwall to that phase


@overeasy I’ve revamped my monitored circuits to combine my power into one CT, light into one CT and AC into one CT. That’ll free up 3 spare CTs for the inverter output (already had one flagged for the battery). Just waiting on some extensions to arrive so they’ll reach.

@craigcurtin correct assumptuon on the self consumption mode. Solar is about 1 year old now, so we got in without having to provide SAPN control (for now). I wonder if shifting to the blue phase would just let the red phase rise? When we first got the solar installed we were getting spikes to 265VAC. SAPN have stated this is the best we’ll get for now, my monitors show spikes overnight to 253/254, but SAPN just point to the solar now :man_shrugging:

Got a sapn power outage coming up, so I’ll be looking to complete the install then. My switchboard is chock full, so it’ll be a total disconnection of circuit breakers to get in there properly and try and make it neat. Will post some follow up data captures afterwards.

FYI - I’m a sparky, but my main gig at work is AC controls, so don’t do a heap of work on domestic or power monitoring (some domestic sparkies might cringe at me calling myself a sparky :stuck_out_tongue_winking_eye:)

Yeah well if you can do the work yourself then i think it would be worth it to juggle the phases around and see if you can bring down the voltage.

Its a shame that the 3 phase inverters are not smarter and actually balance their output based on the voltage of each of the circuits (rather than just outputting the same amount to each phase)

Its pretty incredible just how bad the grid is - our base voltage (overnight) is around 250v on all 3 phases - you would think they could start addressing it and getting the voltages down to where they are meant to be