Two approaches to solar install. Thoughts appreciated!

[Corindikev]

If you can work out what your average power usage in kWh is in a 24 hour period in both Summer & Winter conditions get a battery that can provide at least this amount and a hybrid inverter that can supply what you are likely to need from the battery at peak times like cooking dinner, heating etc.

I installed a 10kW inverter, 18.64 kWh battery & 8.8kW of bi-facial panels in November 2025. Without using air conditioning but normal evening usage like lighting, TV, cooking a fridge/freezer, upright freezer & bar fridge etc the battery depletes to around 70-75% overnight. On sunny days it is fully charged again by 10am & then it begins to export to the grid.

The maximum output current from the battery/inverter is 46 amps or 10.6 kW at 230 volts, quite sufficient for our household.

When we have had hot 35 deg plus days the aircon runs all day and most of the night. The battery has depleted to 20% at the most overnight. If the next day is cloudy it takes most of the day to re-charge.

Note we are 29.5 deg South of the Equator & these values are from December to the end of February so Summer. Our Summer days though are not as long as those at higher latitudes.

Winter values will be interesting & after a year I will be able to decide whether I need to add any modules to the battery in order to go off grid which is my goal.

 

[T1 Terry]

Just had a customer here from yrs back to get a balance installed on his Landcruiser house battery. Over lunch he was telling us about the new solar/inverter/battery had had installed at their house, 18kW solar, 48kWh battery and 16kW inverter. He is with Amber and last mth alone, he cleared $1,500 tax free by having Amber do the trading of his available stored electrical energy.

Now I'm in two minds as to going full off grid or keeping the grid for the opportunity to receive free or actually being paid to draw energy from the grid and store it in the batteries, then sell it back when the price is high enough to make it worth reselling.

The proposed $5 just to be connected to the grid, soon evaporates when you consider the $150/mth to be connected to the grid yet money actually going into the bank account at $1500/mth and the house being powered completely from solar and battery ......

If we never connect the new house to the network, there can never be a fee introduced because the network still has the wires to the house, we just don't want to use it.
Because the govt of the day sold off the poles and wires to private enterprise, they are not allowed to force members of the public to pay a fee to a private enterprise ....
We get a water bill because the mains run a trickle feed past the property, we don't use it, but it is a govt owned enterprise so they can demand payment.
We don't have sewerage, never been run out the 2.5 km we are from town, so it's not there so we don't have to pay for it.

T1 Terry

 

[Everest]

The plan is to place the extra battery on his property, on a wall that faces on to my house ( I'm in a mid terraced house)

Sounds like a good plan - it will look in keeping with the extra 8 panels that you snuck onto his roof

 

[MattyS]

Well,

My solar and battery are all installed and running. After a bit of a saga because of a very minor but crucial oversight by the installers that has taken almost a week to rectify, I have 7.36kWh array , 3.68 each on my ESE and WNW facing roofs.

Also because of this oversight I have a 10kW inverter and not the 5 I was quoted for. I'm just waiting for my export to be activated by Octopus.

I've set up modbus and home assistant to monitor.

 

[Gadget Geek]

Good timing with the weather as well.

Welcome to the solar club.

 

[MattyS]

Good timing with the weather as well.

Welcome to the solar club.

Thank you! Its been a bit of a stressful time but Its all done now. Phew.

 

[Bam Bam]

Well,

My solar and battery are all installed and running.

Fantastic!

After a bit of a saga because of a very minor but crucial oversight by the installers that has taken almost a week to rectify, I have 7.36kWh array , 3.68 each on my ESE and WNW facing roofs.

Nice.

Also because of this oversight I have a 10kW inverter and not the 5 I was quoted for.

Wow - did the DNO approve that? Or are they going to have to de-rate it to 5kw?

Does it offer 10kW discharge from the battery? That would be very hand for backup purposes!

Even if it is 10kW only during sunny times that would be great.

I'm just waiting for my export to be activated by Octopus.

This can take a long time. In the meantime you can try to use as much yourself. Easier to do if you have an EV!

 

[MattyS]

Fantastic!


Nice.


Wow - did the DNO approve that? Or are they going to have to de-rate it to 5kw?

Does it offer 10kW discharge from the battery? That would be very hand for backup purposes!

Even if it is 10kW only during sunny times that would be great.


This can take a long time. In the meantime you can try to use as much yourself. Easier to do if you have an EV!

One of the outstanding issues for me is that the DNO have been advised that a 5kW inverter version has been installed. As far as I know , the DNO records have not been amended. It was limited by the installer to 5kW.

I believe that it allows for a DoD of 5%. so its around 9.5kWh actual usable capacity.

 

[johnb80]

One of the outstanding issues for me is that the DNO have been advised that a 5kW inverter version has been installed. As far as I know , the DNO records have not been amended. It was limited by the installer to 5kW.

I would suggest you adjust it so that export is limited to 5kW but you can use the full 10kW capacity in house.

 

[Bam Bam]

One of the outstanding issues for me is that the DNO have been advised that a 5kW inverter version has been installed. As far as I know , the DNO records have not been amended. It was limited by the installer to 5kW.

If they've limited it then you're fine.

Hopefully it means that the inverter will last longer, though I suppose there is a worry it might not start up as quickly or something. You can check the differences between the start up voltages for both types on the spec sheet. Sometimes it makes no difference so you've got no issues.

Would be great if they could allow 10kw when in off grid mode (if you have that) or fulfilling house load (as John mentioned), but limit to 5kw when exporting to the grid. Though I don't suppose anything so clever would be possible.

I believe that it allows for a DoD of 5%. so its around 9.5kWh actual usable capacity.

That's the battery capacity so a separate matter. Is it a hybrid inverter (DC-coupled)?

If so there is the possibility that if there is battery capacity available in the middle of a sunny day you could exceed the 5kw limit anyway. Although with your array directions you might not ever get full sun on both. Maybe at 2pm or something at the hight of Summer you could get a tiny bit of clipping.

 

[johnb80]

Would be great if they could allow 10kw when in off grid mode (if you have that) or fulfilling house load (as John mentioned), but limit to 5kw when exporting to the grid. Though I don't suppose anything so clever would be possible.

Thats pretty much standard on all approved inverters. You simply set Maximum Export Power on my Victron it's in Kw and on my Growatt it's a % of the inverter power. It simply does exactly whats said on the tin, in MattyS's case he just needs to limit Export to 5kW but leave the inverter maximum power at 10 kW as long as his batteries can cope with a 10 kW draw from them (less and solar PV at the time).

 

[johnb80]

This is how it looks on the Growatt SPH

and the Victron Multiplus II

I dont have a lot of experience on parameters within inverters but the ones I've had dealings with all have this facility.

J

 

[Rolfe]

I would suggest you adjust it so that export is limited to 5kW but you can use the full 10kW capacity in house.

Can you do that? It's what I was going to say, but I didn't know if it was possible.

 

[johnb80]

Can you do that? It's what I was going to say, but I didn't know if it was possible.

Absolutely YES. Most recent inverters to my knowledge are G100 compliant and can do this. You can check on the ENA list here G100 Approval List When I first installed my Multiplus II GX it was going through the approval process so I had to limit the export to 0kW. Now it's approved the restriction is removed and I can set the maximum export to the DNO agreed value.