3KW or 5KW setup - please advise

Rouxenator

Rouxenator

Dank meme lord
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Background : I have a sweet 1KW solar setup from my initial thread. Big thanks for those that shared their knowledge and experience there.

My 1KW setup is working like a dream, when the sun is out, I can run my PC, TV and washing machine off it and it does not dip into the battery. Naturally I now want more so I can have it wired to the DB and run all the lights and plugs in the house. We draw very little power, I don't think we will exceed 2KW (TV, PC, lights, fridge and maybe microwave occasionally).

Limiting factor here is roof space. I can only fit 3 panels on my roof and I already have one 545W JA panel. The idea is to add 2 more with my upgrade, but here comes the tricky part. If really needed I can add 1 more panel on the flat roof above the stoep.

From the homework I have done it seems a 24volt 3KW inverter will be a good fit considering my solar setup and needs - but bigger is tempting. The panels kick out about 40volt so 3 of them in parallel will fit nicely in the 3KW's MPPT range of 30-120VDC. I can also save a bit in the battery department since I already have a nearly new 200ah 12V Vision and adding another in series will cost about R6k. No, it's not lithium but it will work for now.

The guy that did my last install said he can get me a 5KW Lux Power SNA5000 unit that is also nearly new from someone he did an install for and shortly after wanted to upgrade to 7KW - sweet deal.
I am happy with the work of this guy, and I like the deal he put together for me:
  • 5kw Hybrid Inverter Lux Power SNA5000 ( Used ): R8,000.00
  • 5Kw Battery ( Lithium ): R26,460.00
  • Powit 550w solar panel x 2: R8,500.00
  • Sub D.B. Board: R1,800.00
  • Installation: R5,000.00
Total: R49,760.00

However, I have some concerns that I hope to get feedback and clarity on:

1) All 5KW/48V inverters I have looked at only start solar charging at around 120V, this Lux Power for example says Solar start voltage 100V (+/- 10V) and PV MPPT array voltage 120V~385V. Putting 3 panels in series should cover that, but it feels like it's cutting it close. My current panel does about 35V to 45V from what I observed, so 105V~135V for 3 in series.
Should I rather go 3KW with the panels in parallel instead? Or try to add a 4th panel somewhere?

2) Is there a big difference between the JA panel I have and these Powit ones? I am not sure if solar panels are like monitor panels and there are only a few factories making them and everyone slaps a badge on them so technically they will be the same? Or are there a bunch of different makers and going for a known brand is important?
Should I rather buy my own 2 additional JA panels instead?

3) This I could probably ask the installer, but while I'm at it here, the sub DB board, does that include an override switch that will bypass this whole system and have my house run like it is now, connected directly to Eskom? If say you need to swap batteries, or the inverter dies or some eventuality with the setup?
Should an override be included, or must I ask for it?

Hoping some of you can give your feedback and suggestions on this. I am not at all knowledgeable on this, but I do know asking around here helps a lot, as it got me where I am now.
 
Not an expert by any means, YMMV:
That inverter sounds very cheap (even for used). Is it a true hybrid, or the off-grid model (totally different product)?

You get what you pay for in terms of built-in MPPT efficiency and voltage flexibility. 48V systems allow for much more future expansion, and panels are super cheap. If space is limited, buy more small ones, rather than few large ones.

Any plugs are likely to hit 3kW load at some point, unless you have super-tight control of the home, and all of it's occupants.

3. Any system connected to the DB must have a changeover switch, if it is to meet the CoC requirements. It's not super expensive, and pretty standard.
 
Rouxenator said:
Background : I have a sweet 1KW solar setup from my initial thread. Big thanks for those that shared their knowledge and experience there.

My 1KW setup is working like a dream, when the sun is out, I can run my PC, TV and washing machine off it and it does not dip into the battery. Naturally I now want more so I can have it wired to the DB and run all the lights and plugs in the house. We draw very little power, I don't think we will exceed 2KW (TV, PC, lights, fridge and maybe microwave occasionally).

Limiting factor here is roof space. I can only fit 3 panels on my roof and I already have one 545W JA panel. The idea is to add 2 more with my upgrade, but here comes the tricky part. If really needed I can add 1 more panel on the flat roof above the stoep.

From the homework I have done it seems a 24volt 3KW inverter will be a good fit considering my solar setup and needs - but bigger is tempting. The panels kick out about 40volt so 3 of them in parallel will fit nicely in the 3KW's MPPT range of 30-120VDC. I can also save a bit in the battery department since I already have a nearly new 200ah 12V Vision and adding another in series will cost about R6k. No, it's not lithium but it will work for now.

The guy that did my last install said he can get me a 5KW Lux Power SNA5000 unit that is also nearly new from someone he did an install for and shortly after wanted to upgrade to 7KW - sweet deal.
I am happy with the work of this guy, and I like the deal he put together for me:
  • 5kw Hybrid Inverter Lux Power SNA5000 ( Used ): R8,000.00
  • 5Kw Battery ( Lithium ): R26,460.00
  • Powit 550w solar panel x 2: R8,500.00
  • Sub D.B. Board: R1,800.00
  • Installation: R5,000.00
Total: R49,760.00

However, I have some concerns that I hope to get feedback and clarity on:

1) All 5KW/48V inverters I have looked at only start solar charging at around 120V, this Lux Power for example says Solar start voltage 100V (+/- 10V) and PV MPPT array voltage 120V~385V. Putting 3 panels in series should cover that, but it feels like it's cutting it close. My current panel does about 35V to 45V from what I observed, so 105V~135V for 3 in series.
Should I rather go 3KW with the panels in parallel instead? Or try to add a 4th panel somewhere?

2) Is there a big difference between the JA panel I have and these Powit ones? I am not sure if solar panels are like monitor panels and there are only a few factories making them and everyone slaps a badge on them so technically they will be the same? Or are there a bunch of different makers and going for a known brand is important?
Should I rather buy my own 2 additional JA panels instead?

3) This I could probably ask the installer, but while I'm at it here, the sub DB board, does that include an override switch that will bypass this whole system and have my house run like it is now, connected directly to Eskom? If say you need to swap batteries, or the inverter dies or some eventuality with the setup?
Should an override be included, or must I ask for it?

Hoping some of you can give your feedback and suggestions on this. I am not at all knowledgeable on this, but I do know asking around here helps a lot, as it got me where I am now.
Click to expand...
You can't add a 4th panel "somewhere" in series as the string adopts the power of the weakest panel afaik.
 
Gordon_R said:
Not an expert by any means:
That inverter sounds very cheap (even for used). Is it a true hybrid, or the off-grid model (totally different product)?

You get what you pay for in terms of built-in MPPT efficiency and voltage flexibility. 48V systems allow for much more future expansion, and panels are super cheap. If space is limited, buy more small ones, rather than few large ones.

Any plugs are likely to hit 3kW load at some point, unless you have super-tight control of the home, and all of it's occupants.

3. Any system connected to the DB must have a changeover switch, if it is to meet the CoC requirements. It's not super expensive, and pretty standard.
Click to expand...
They still take up the same surface area. He already has one panel.
 
wingnut771 said:
They still take up the same surface area. He already has one panel.
Click to expand...

You can buy half-size panels, and mount them in the same surface area, to make up the necessary MPPT voltage. The existing panel will not fit the narrow specifications he is trying to achieve.

Edit: He also needs to look carefully at shading issues, since the whole string needs illumination. Lots of factors to consider.
 
That Luxpower is a decent inverter, sitting slightly above the normal voltronic / axperts and just below the SS/Deye. We have one running at my mom-in-laws place and it just works
 
It does not seem like you have the required roof space to have a 5kw inverter. You really do need at least a 5kw inverter. A Sunsynk 5kw needs 4 panels per array. Splitting the array is not a good idea with Sunsynk type inverters. You can try find smaller panels that could fit 4 in the space. I would sell the house and buy a place with proper solar capability.
 
Gordon_R said:
You can buy half-size panels, and mount them in the same surface area, to make up the necessary MPPT voltage. The existing panel will not fit the narrow specifications he is trying to achieve.

Edit: He also needs to look carefully at shading issues, since the whole string needs illumination. Lots of factors to consider.
Click to expand...
Doesn't half size have half volts?
 
There is always the option of not putting the panels on the roof if there is not enough space, a simple structure can be built to install them or you can improvise something on the side of the wall, even ground mounted structures are an option.
 
Last edited:
Maybe get a 3kw with 4 small panels that will fit. Or maybe a 3kw has less minimum panels per array? Then also use your current system with 1 panel on the garage. Best is to sell and move to Scummerset West, mtb is better there.
 
wingnut771 said:
Doesn't half size have half volts?
Click to expand...

All panels produce much the same voltage. Half-size panels produce less current, but if you use more of them the total power will be the same (per unit surface area).

Off-topic, but most modern/large panels are half-cut, with more cells, but wired in two parallel strings (a totally different scenario). This means that panels in partial shade will still produce some power.
 
Sounds like 5KW is the way to go then. In terms of panels are they basically all the same with different names on, or will there be a difference between the JA one I have now and the two Powit ones being added?

Getting 45volt from my single panel now so in full sunlight 3 should produce enough voltage for the MPPT on the Lux power to do its thing.
 
Rouxenator said:
Sounds like 5KW is the way to go then. In terms of panels are they basically all the same with different names on, or will there be a difference between the JA one I have now and the two Powit ones being added?

Getting 45volt from my single panel now so in full sunlight 3 should produce enough voltage for the MPPT on the Lux power to do its thing.
Click to expand...

Don't confuse the maximum (open circuit) voltage rating of a panel, with the actual voltage once it is supplying power. The difference being due to the internal resistance of the cells, plus all of the wiring between the panel and the inverter.

Also remember that output is temperature dependent, so your reading in winter may not be representative of hot midsummer days.

Going with the bare minimum voltage may not produce the best year round efficiency from your system.
 
Gordon_R said:
Don't confuse the maximum (open circuit) voltage rating of a panel, with the actual voltage once it is supplying power. The difference being due to the internal resistance of the cells, plus all of the wiring between the panel and the inverter.

Also remember that output is temperature dependent, so your reading in winter may not be representative of hot midsummer days.

Going with the bare minimum voltage may not produce the best year round efficiency from your system.
Click to expand...
Very good point - I did not take seasonal changes into account.

Perhaps I should just go with my gut feel and stick to the 3KW idea I initially had.
The benefits are it is more affordable, albeit partly due to sticking to AGM batteries for now, and with only 3 panels the 3KW should work with a bigger margin for seasonal and weather variances.
The downside being it will not provide as much power and the AGM batteries will wear out sooner than Lithium but at that point I can revisit the situation.
Storage capacity will be almost the same since I will be adding another 200Ah to the one I have giving 4.8Kw in total.
 
Rouxenator said:
Very good point - I did not take seasonal changes into account.

Perhaps I should just go with my gut feel and stick to the 3KW idea I initially had.
The benefits are it is more affordable, albeit partly due to sticking to AGM batteries for now, and with only 3 panels the 3KW should work with a bigger margin for seasonal and weather variances.
The downside being it will not provide as much power and the AGM batteries will wear out sooner than Lithium but at that point I can revisit the situation.
Storage capacity will be almost the same since I will be adding another 200Ah to the one I have giving 4.8Kw in total.
Click to expand...
You know you can get 5kW that works from 60V? You have plenty of choices, you don't have to settle.
 
This Mecer MPPT is between 60 to 115V, with a 145V max voltage. There is an inverter for every application out there if you look hard enough.

Screenshot_20230715_115907.jpg
 
Rouxenator said:
Very good point - I did not take seasonal changes into account.

Perhaps I should just go with my gut feel and stick to the 3KW idea I initially had.
The benefits are it is more affordable, albeit partly due to sticking to AGM batteries for now, and with only 3 panels the 3KW should work with a bigger margin for seasonal and weather variances.
The downside being it will not provide as much power and the AGM batteries will wear out sooner than Lithium but at that point I can revisit the situation.
Storage capacity will be almost the same since I will be adding another 200Ah to the one I have giving 4.8Kw in total.
Click to expand...
What batteries were you going to use with the 5kW?
 
wingnut771 said:
Ah, so you're going lithium with the 5kW but keeping LA with the 3kW?
Click to expand...
Yes - since I already have 1 nearly new 200Ah AGM if I do go 3kW the easiest way to reach 24volt is to buy another. For 5kW it makes more sense to just go lithium.
 
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