Prioritising inverters - Enphase and Fronius load balancing

Hi All,

First time post - please be gentle!!

In way of background I have just had installed 2 new, Fronius inverters, one on each of the two phases that I have. One of these is linked to a BYD battery stack. Both are connected to separate arrays of solar panels on my roof.

In addition to this, I have an Enphase system with 30 panels and micro inverters. This is about 7 years old and generates, at peak, about 8kW.

Due to the area I live in being saturated with solar, the old system (Enphase) is the only one that is allowed to export to the grid, the two new Fronius systems are not allowed to export.

The issue I’ve got is based around “priority setting” if this is at all possible.

What I saw yesterday was that the load on the house was about 3kW. It was a sunny day and the Enphase system was able to pump out 8kW - which it did - satisfying the load from the house and exporting about 5kW to the grid. The batteries were already full so the new inverters were just sat idle.

What I’d like to happen is the NEW inverters to take priority and satisfy the load from the house (and the battery fill if necessary) and then the Enphase system could either top up any demand from the house but otherwise expert the full 8kW that It can produce. At the moment it seems that the Enphase is “trying to do everything” and effectively make the two new inverters redundant once the battery is full if the house load is below the capability of the old system.

Is this possible ? I’m guessing it’s not something a customer can do directly (I do have Home Assistant integrations for both the Enphase entities and the new Fronius ones - but I’m thinking it’s probably too embedded to change that kind of thing) but is there anyone out there that has had a similar issue and found a solution?

Thanks is advance for any insights or potential solutions.


Hi Andy,

In Australia, solar systems are export-limited to 5kW per phase, so you cannot export more than 5kW from the Enphase system.

I’m assuming you have the Enphase system on one phase? If so, then you could simply transfer solar loads to the other phase, which is connected to one of the Fronius systems, and take some demand away from the Enphase.

Hi Jason,

Thanks for your message, and your consideration of the issue.

The Enphase system is actually on both phases – so I can export 8Kw (allowed to).

It’s actually sort of sorted itself out. The sparky moved the envoy read point to between the grid and the first meter that is linked to the Fronius – this is now reading as the consumption (on the envoy) but it actually the draw on the grid – the amount imported – which is what I was looking for.

It is showing me that when the load in the house (across both phases) is covered by the two new Fronius inverters, they shoulder the load and whatever the enphase system can generate is going back to the grid.

The issue I have now is that, with the batteries only on one phase, in the evening I end up using grid power when there is sufficient in the battery to do both. I can’t fix this unless I get more batteries and add them to the other phase.

I might move some circuits across to the other phase – as, at the moment, I’m getting up in the morning and the batteries are still at 35% - and I’ve been importing all night on one phase.

Might wait till I’ve been through a winter to see how it all works.

As I’m on AMBER for my grid power (retailer that offers wholesale, fluctuating rate (every 30 mins the price changes) I will set the battery up to never turn on before 3pm (as that’s when the price goes up) – it’s cheaper for me to import during the day if I need to and save the batteries to the evening when the price spikes.

All very interesting and I’m learning heaps.