Here @ LifeInGalicia & LemosVerde we use a simple modular system.
This is based on the famous German “Balkonkraftwerke”. Two panels and a micro inverter connected to AC cabling and feed in points. At the time of writing such a module costs about 390€. Depending on the instal situation staging (fixing) of these can cost from 75€ onwards. 
For me the huge advantage of an AC coupled system is extreme modularity, add when more is needed, no special precautions are needed, no DC high voltage (e.g. 3-400 Volt DC is quite deadly), shade or faults only affects one maximal two panels as each panel is on its own MPPT tracker.
During the Gorilla years I just bought panels and an inverter when it was cheap, yes I also tested no name inverters (promptly bought twice) and cheap Chinese single panel ones (surprisingly still working).
Storage story
Stumbling across Victron and its Multiplus series with its marine history was a good send.
These units are designed for a rough environment (E.g screws are all stainless steel) and quite forgiving.
The software is adequate and regularly updated if required. Again a wide variety of acceptable external systems allow for easy customisation and installation. The ability to work as a UPS was highly attractive as we faced and face regular power disruptions. Control, adjusting, updating all can be done OTA (Over the air) no special cabling or connection is required.
For batteries I elected Pylontech LiFePO US3000C series @ 3.5 kWh with 3.2 kWh usable. I bought batteries at various ages and production types (one is a Slovenian make), they do have different firmwares depending on chip set used, which is important to know if there is a problem and you need to upgrade this.
Victron MP has limited access to the internal data of these batteries, it can show lowest and highest cell voltage as well a temperature. It is enough to see eventual cell drifting. To gain more insight you do need a special cable and software.
The most important thing is to balance the batteries upon installation. This may take time. Also running some full cycles (E.g. SOC 100 – 10%) help to establish and balance them well.
Battery insights:
The pylontech batteries are rated at 6000 cycle to degrade to 80%. To gain insights you need BatteryView a freely available software and a special RJ45 cable. I ordered a standard USB to Cisco router cable – spliced it – cut it open carefully exposed the wires – cut wire 5(black) and 8(green) – reconnected 5 to 8 directly and got communication (no soldering just twisted them tightly). With this you can get insight of cells, history and update the firmware, if so directed by their international support.
After two years working flawlessly I had an issue of alerts – spiking voltage on one unit – which was resolved after updating the firmware send by pylontech. This was a rare sampling error from a chip set.
It was noticeable on the VRM dashboard (Victrons cloud control) detailed graphs and I send these to pylontech and got a response within 24h including the recommended firmware. Updated with BatteryView and it is working ever since.
During this time the battery was simply taken out of service (switch off) , without further disrupting normal operations.
There are various discussions around, I simply run these batteries at 52.4V max. This gives some room for over shooting at charging, switching as well as temperature fluctuations, as my storage environment can go 10 – 26C.
Overall settings:
As we have a parallel AC installation the Multi can not know the full PV production and demand. Therefore we use an external CT, which is extended by 5 meters with a high quality headphone extension.
With this the Multi can see power demand and direction at connection point of the grid. This enables the standard software (ESS) to charge or discharge the battery to get our external supply to close to 0 (actually we set this to 40W). Voltage fluctuations make it impossible for the unit to exactly balance.
I do not like to run equipment to 100% of capacity and there are some restrictions I activated within the standard settings of the unit.
Charge current max. @ 30A – SOC min @ 30% – Inverter load ideal @ 1000W max. – Max voltage of batteries @ 52.4V – Grid-set @ 40W.
Because of the CT the unit will draw sudden demand from battery and grid, then balance out.
Power management:
Now it is the latest hype but actually needed and the standard software can simply not fulfill our needs.
Years ago we started using OpenHab on a Windows box. NodeRed on the GX I rejected as I did not want to run another software on the device and potentially crash it. Also some interfaces where simply not available at that time.
Our houses where already on Sonoff devices (S26) which can be used without changing the firmware. Simply installed additional TPlink devices on the feed in lines and on power hungry devices like washing machines, dryer etc. to see if they are actual producing respectively demanding. The only issue is one cant set fixed IP, this needs to be done on the router and sometimes need a while to establish after network recoveries, but it is plug and play. Both, Sonoff and TP, have cloud apps and can be controlled manually from anywhere, if required. The router is on the UPS string !.
Again we are not interested in selling power or feed in, we use what we get – summer and winter -.
Hot water 80L & 10L have two heating elements of 1kW each, only one is ever active. Yes, it takes longer to heat up but overall it does not matter if one uses 1 or 2 kW, just 1kW is easier to switch.
We have towel heaters and underfloor warming in segments – each of those have between 400 – 500W and are plugged into Sonoff´s as well.
What I call priority units, like aircon, pellet ovens, fridges, well pump etc etc are not directly controlled. They are partially on the UPS string (AC1 out) but simply have to run if required and grid is available.
This gives direct control over a total of about 5kW switchable loads and some indirect distribution of power – whats left on the table.
Production is on average – spring to autumn – 20kWh daily – in winter less. Should we need more we can simply nail some panels on a south facing facade, specifically for winter.
Software part:
The software can control all the above mentioned units up to 5kW. The function is quite simple. Check what is coming in/out, check what is used, calculate what could be used, taking into account the SOC of the battery , with rising SOC there is less left on the table for the battery and switch on or off (WiFi) by priority or set allocations (e.g. 1 – 4 hours/day). Whenever demand fluctuates by +/- 5% the routine is triggered, thus being more “aggressive” the less is available. All switches reset automatically after 60 minutes, so if the network or a segment fails, all is off after latest 1 hour. There is also an override function so on two consecutive rainy days hot water maybe available.
Peak demands are balanced off by using the grid, which I pay for.
Peak PV production is around 4.5kW, max. this year was 25kWh/day. We have a prolonged and flat curve due to various orientations and the modular design of our PV.
Over the last month (summer) we have managed to feed in about 0.5kWh and used about 1-2kWh/daily from the grid. Remember this powers three houses. 1 lived in and two holiday homes.
Here in Spain you pay for the max allowable power of your connection – about 55€/year per 1kWh. We get away with contracting just 3kW.
We are on a fixed contract @ 0.15€/kWh all in, all day every day. The software can easily be extended to cater for flexible tarifs @ the moment @ 60 kWh/monthly it is just not worth the eford.
For next year I am working on a round robin system to prevent more than one washing machine / dryer at a time included in a simple information system for us and our guests.
