Hi everyone

I'm looking at doing a new full installation for my house with the idea of maximizing on solar energy and trying to go through the evening on battery power to significantly reduce my bill and dependency on Eskom.

Initially I was thinking to get 1 x Solis 8kw inverter, 10-12 solar panels (4 x South West roof and 8 x North West roof), and a Dyness 14.3kwh battery.
But then I compared prices and 2 x Solis 6kw inverters seems to make a bit more sense in terms of cost, and capacity, etc. (10kw Sunsynk or 12kw inverters are slightly out of my budget)

Another reason for 12kw in total, is that I just want to place all my home circuits on the inverter, perhaps with an additional changeover to kitchen/geyser as a means to remove that load. But essentially, I want to heat the geyser on solar, etc. But mainly, I dont want to overload the inverter when for example heating the geyser, dishwasher running and then water pump kicking in causing a spike and then getting a beeping inverter (even while being on eskom supply pass through and not battery), if you know what I mean.

So basically, can anyone give some recommendations please? I think 2 x 6kw inverters in parallel makes sense in terms of size and also some redundancy incase one is faulty and need to go for repairs, then you atleast have another one.

So in summary, is a parallel inverter setup still reliable without any syncing issues and power delivery/ load issues? or will a single inverter be better? Any gremlins that people experience with parallel setups?

Thanks in advance
Q

As someone with a Solis S6 6kw inverter, I think your reasons all resonate and are well thought out especially as regards redundancy. Just make sure you have enough space to ensure there's adequate "breathing space" (colloquialism) around the inverters as per Solis guidelines if I remember well it's 500mm all round or something to that effect.

I also went with the Solis due to cost factors as well vs the Sunsynk and given that Sunsynk was only 5Kw, so the headroom (extra 1kw) for me, made sense as well. Battery-wise you may also want to consider redundancy in your equation as well, otherwise if the 1-battery packs up or is faulty you're in the dark safe for during the day when you can run off your panels. Also when adding another battery, you'll have to add a similar size battery and if it's large, then you also get hammered, cost-wise.

Edited August 15, 2025Aug 15 by Moffat

OK cool, thanks for taking the time to reply.

I checked, luckily the 6kw Solis only needs 150mm between inverters, but 500mm above the inverter and then 800mm above floor level, so space should be sufficient.
The reason I'm going with the 14.3kwh battery is that it works out significantly cheaper than buying individual 5kwh batteries, and more space saving. Only downside as you've mentioned it that you need another large one when you expand, but I feel it will still work out cheaper. So I will start out with 1 x 14.3kwh battery and see how it lasts through the evening (should be enough).

1 hour ago, Qtin said:

OK cool, thanks for taking the time to reply.

I checked, luckily the 6kw Solis only needs 150mm between inverters, but 500mm above the inverter and then 800mm above floor level, so space should be sufficient.
The reason I'm going with the 14.3kwh battery is that it works out significantly cheaper than buying individual 5kwh batteries, and more space saving. Only downside as you've mentioned it that you need another large one when you expand, but I feel it will still work out cheaper. So I will start out with 1 x 14.3kwh battery and see how it lasts through the evening (should be enough).

The other important consideration as you 'pull the trigger' on your purchase is ensuring that the battery supplier has a robust after-sales service regarding your battery so that you can always have online and in person support should anything go wrong with your battery and that they have a good app which enables you to see what's happening with the individual cells and temperatures, not to mention a good warranty history that is efficient.

The question of redundancy is I guess something you must go with your gut on. If you install a bypass switch, which you probably should, you could still run on the grid, and my personal 2c is that the loss of not generating power for the couple of weeks you'd be idle for repairs, is not going to outweigh the cost of the upfront installation of a 2nd inverter. Different story if you're off-grid.

Looking at the specs of your system, to just go with a single 8kW Solis, and just install non-essential loads like the geyser to the grid port. This is considering the recommended 0.5C discharge rating on the 14.3kWh battery, and the approx 6-7kW of panels to be installed, and the 50A pass-through of the inverter, 200% 10-second surge rating of the inverter, I think at least on paper you'd be fine.

Otherwise, if it's a question of the capacity of 2x6kW Solis inverters, maybe even to consider future expansion with another 14.3 battery, you could consider maybe a single 12kW Solis S6 inverter for just a shade over the cost of 2, and not worry about any issues of running in parallel mode. Available on the powerforum store website.

Last comment, would be to avoid installing panels on your South-West roof if you can, rather fit it all pointing Northwards.

Edited August 16, 2025Aug 16 by GreenFields

59 minutes ago, Moffat said:

The other important consideration as you 'pull the trigger' on your purchase is ensuring that the battery supplier has a robust after-sales service regarding your battery so that you can always have online and in person support should anything go wrong with your battery and that they have a good app which enables you to see what's happening with the individual cells and temperatures, not to mention a good warranty history that is efficient.

Yeah sofar warranties and aftersales support appears to be really good just by reading some forums and with direct interaction with Dyness SA.
App and connectivity options also seems pretty good.

17 minutes ago, GreenFields said:

The question of redundancy is I guess something you must go with your gut on. If you install a bypass switch, which you probably should, you could still run on the grid, and my personal 2c is that the loss of not generating power for the couple of weeks you'd be idle for repairs, is not going to outweigh the cost of the upfront installation of a 2nd inverter. Different story if you're off-grid.

Looking at the specs of your system, to just go with a single 8kW Solis, and just install non-essential loads like the geyser to the grid port. This is considering the recommended 0.5C discharge rating on the 14.3kWh battery, and the approx 6-7kW of panels to be installed, and the 50A pass-through of the inverter, 200% 10-second surge rating of the inverter, I think at least on paper you'd be fine.

Otherwise, if it's a question of the capacity of 2x6kW Solis inverters, maybe even to consider future expansion with another 14.3 battery, you could consider maybe a single 12kW Solis S6 inverter for just a shade over the cost of 2, and not worry about any issues of running in parallel mode. Available on the powerforum store website.

Last comment, would be to avoid installing panels on your South-West roof if you can, rather fit it all pointing Northwards.

Thanks for your 2C's 🙂, it came at the right time.
I was actually busy reading the battery user manual about 10mins ago when it struck me that 12kw might actually be too much for the battery, since a single battery has a 200A max continuous discharge current, and 140A charge/discharge current, and then saw your comment. Just a pity Solis doesn't have a 10kw model, would've been perfect.
Just to confirm, if the geyser is connected to the grid port, can I still use the solar energy generated during the day to feed the geyser? Problem is I have a prepaid meter, so not sure how it will behave when feeding electricity to the Grid port. (I'm a bit inexperienced w.r.t feeding back into the grid).

W.r.t to the solar panels, I can only with 8 panels on the NW (312degrees) side, so thought to add the other 4 on the SE (132deg) side for the morning sun which will help recharge battery drain early in the morning until perhaps 2pm+.

Does the above make sense?

1 hour ago, Qtin said:

Thanks for your 2C's 🙂, it came at the right time.
I was actually busy reading the battery user manual about 10mins ago when it struck me that 12kw might actually be too much for the battery, since a single battery has a 200A max continuous discharge current, and 140A charge/discharge current, and then saw your comment. Just a pity Solis doesn't have a 10kw model, would've been perfect.
Just to confirm, if the geyser is connected to the grid port, can I still use the solar energy generated during the day to feed the geyser? Problem is I have a prepaid meter, so not sure how it will behave when feeding electricity to the Grid port. (I'm a bit inexperienced w.r.t feeding back into the grid).

W.r.t to the solar panels, I can only with 8 panels on the NW (312degrees) side, so thought to add the other 4 on the SE (132deg) side for the morning sun which will help recharge battery drain early in the morning until perhaps 2pm+.

Does the above make sense?

What you are saying makes perfect sense.

Here you should take my comments with a pinch of salt - rather take it from someone who actually uses or installs Solis - because I'm just comparing the operation to my Deye hybrid which is the competitor product, and I'm looking through the manual and spec sheets.

But yes, the theory is, with the CT cable/CT coil that comes with the inverter, it should be able to divert solar and battery power to the non-essential devices on the grid port, and that is all controlled by the current-sensing feedback that this CT cable gives to the inverter. It should inject just enough power to the grid port, so that you don't send power past the CT coil and on to the grid. Works well enough on my Deye, but it only works as long as there is power on the grid. The non-essentials like the geyser would then not be backed up by battery.

Regarding the panels, I think you should find an online solar calculator and work out for your location what would be the actual power generated for those panels facing South-West, before installing them, to see if it's worth it. I understand the thinking to make the best of the situation, it's just naturally sub-optimal. I think your best bet would be to take special attention with the choice and layout of the North-West panels, to get the best in terms of efficiency-level of the panel, outer dimensions, Voltage level, etc to squeeze as much as you safely can facing that direction. On good sunny days the 8 panels should still be enough to replenish your battery

Edited August 17, 2025Aug 17 by GreenFields

20 hours ago, Qtin said:

Thanks for your 2C's 🙂, it came at the right time.
I was actually busy reading the battery user manual about 10mins ago when it struck me that 12kw might actually be too much for the battery, since a single battery has a 200A max continuous discharge current, and 140A charge/discharge current, and then saw your comment. Just a pity Solis doesn't have a 10kw model, would've been perfect.
Just to confirm, if the geyser is connected to the grid port, can I still use the solar energy generated during the day to feed the geyser? Problem is I have a prepaid meter, so not sure how it will behave when feeding electricity to the Grid port. (I'm a bit inexperienced w.r.t feeding back into the grid).

W.r.t to the solar panels, I can only with 8 panels on the NW (312degrees) side, so thought to add the other 4 on the SE (132deg) side for the morning sun which will help recharge battery drain early in the morning until perhaps 2pm+.

Does the above make sense?

Though the battery has a 200A max continuous discharge, in the Solis settings you can still choose not to have the inverter use the full max charge and discharge current and set it to lower levels, which is what I have done within my setup in order to try conserve my battery. Am intending to add another 2 but still will not allow the inverter (using the settings) to draw at maximum for purposes of enabling battery longevity.

On 2025/08/16 at 5:10 PM, GreenFields said:

But yes, the theory is, with the CT cable/CT coil that comes with the inverter, it should be able to divert solar and battery power to the non-essential devices on the grid port, and that is all controlled by the current-sensing feedback that this CT cable gives to the inverter. It should inject just enough power to the grid port, so that you don't send power past the CT coil and on to the grid. Works well enough on my Deye, but it only works as long as there is power on the grid. The non-essentials like the geyser would then not be backed up by battery.

That theory is solid. Precisely how my Solis operates.

Geyser and Oven are the only 2 circuits I classified as non-essential and is wired grid side. All other circuits are on a separate SUB-DB. CT Clamp on incoming grid feed.

Geyser heats up through various ways depending on PV availability. Enough PV and it heats up using solar entirely. Not enough PV it uses a combination of Solar and Battery. Not enough solar and battery (combined), it uses whatever it can from solar, battery and supplements differences from the grid.

If grid is lost, the inverter does not feedback at all to non-essential circuits (by design). For me, that means, Geyser and Oven completely unavailable during grid loss.

Edited August 25, 2025Aug 25 by LumexClipsal
Spelling correction

Hi guys

Apologies for the only hopping back on the forum now. And thanks @GreenFields @Moffat @LumexClipsal for your advice and inputs thus far.

I ended up opting for the 8kw Solis inverter (more within my budget). I got it for a really good price and last bit of stock at Rubicon in PE, and just thought if I need anything bigger later on, I can always just sell the inverter and upgrade.
Also went for the Dyness 14.3kwh battery and 12 x 585W Trina Duomax N bi-facial solar panels, which should be delivered today.[ Calculators show that I should easily be able to generate more than 25kwh a day - even at my roof's NW (8 panels) and SE(4 panels) direction]

Managed to chat to an installer yesterday and he confirmed that you can indeed power your household items on the grid side without tripping your prepaid meter, just need to add a bias of 20-100w, then your meter wont trip (tamper) or detect the additional supply. So this will be great to power things like the geyser, dishwasher, washing machine during the day without affecting the inverter 8kw limit too much.

But I'm just trying to figure out the most effective way to transfer these non-essential items on the Grid port to the Backup port incase of a power outage (since you cant feed back into the grid when there is no eskom power available).

Guess an additional changeover should do the trick, otherwise I need to use a Siemens Logo (have a spare one) and some relays?

Anyone with a similar scenario and solutions perhaps?

I have the Solis 8kw, I switched on all that I could in my house, geyser stove kettle pool etc, maxed out at 9.8 kw running purely on solar. As far as I know the 8 kw can push out up to 12kw

3 hours ago, Shockin said:

I have the Solis 8kw, I switched on all that I could in my house, geyser stove kettle pool etc, maxed out at 9.8 kw running purely on solar. As far as I know the 8 kw can push out up to 12kw

Does this not kill the life of the inverter? I rarely if ever go over 70% of my rating.

6 hours ago, Denns said:

Does this not kill the life of the inverter? I rarely if ever go over 70% of my rating.

The total PV output is 12.5kW, so if this was say 6kW AC loads and the rest charging batteries, it's still well within rated power. Not enough info to say. Exceeding the 8kW AC output should not be normally possible.

1 hour ago, GreenFields said:

The total PV output is 12.5kW, so if this was say 6kW AC loads and the rest charging batteries, it's still well within rated power. Not enough info to say. Exceeding the 8kW AC output should not be normally possible.

I understand now. Thanks for the explanation. I had assumed he was talking about the AC output.