Hello everyone,

With the repeated power outages in my gloriously well run ANC-EFF coalition city of Ekurhuleni near JHB, it's time for a more substantial investment in power which has led me here for advice.

House of 3-4 people. Electric geyser for one bathroom with bath+shower (no timer yet). Two fridges. Aircon. Electric heater. Jojo pump used mostly during water outages.
Gas geyser outside the other bathroom (shower) and gas heater for the lounge.
18kWh daily usage (10 during sunlight hours, 8 at night) excl stove which works out to 558kWh/R1950pm. Another 50kW for a stove which works out to R175pm. Plus the service fee of R240pm

Looking at the following which would be for the whole house excluding the stove, and I think the stove would .

• Deye 12kW Hybrid Single Phase inverter. This is typically the maximum I see recommended by municipalities for our main switch which is 63a.

  The 12kW inverter is great for our peak loads and the 12kW single phase model offers a third MPPT over the 8kW.
  

• 2 x Deye 16kW Lithium Batteries. Costs a little more than 4x5.12kWh batteries for a lot of storage on a sunny day that should hopefully help if followed by a cloudy day.
  

• 10 x JA 605w bifacial N-type Topconn panels on a section of zinc roof that 345 degrees NNW on two MPPTs (5 panels each).

• 5 x JA 605w bifacial N-type Topconn panels on a section of zinc roof that is 75 degrees ENE. Would sadly be affected by a neighbour's large tree till around 8am (nope, owner won't trim it).

  Panels are 52.6v VOC * 5 = 263v, so adding 15% for temperature variation in JHB would be 302v which won't exceed the MPPT range of 150-450v.

  This would be maximising our generation, as the WSW side could only take 3 panels and the SSE side could only take 6 panels, both of which are worse than the ENE array.
  Based on measurements there might be a chance of making each array 6 panels instead of 5 (18 panels instead of 15) without exceeding MPPT voltage, but will see what fits comfortably during installation

A neighbor with solar+gas also suggested switching the electric stove over to a gas 5 plate stove, with an electric oven that could then run on the inverter. But I must admit that I am a bit apprehensive about copper gas pipes running in the kitchen to an outdoor bottle which involves a significant length of piping and the cost would mean one less battery.

Any advice is appreciated, this is all very new to me and involves a huge savings cost involved (paid off house so no home loan to draw from)

Plan looks solid - if you can get 18 panels then go for it - panels are the cheapest upgrade and if you can max those as far as possible then go for it - it will help you even on a cloudy day.Spend an extra R600 and get a geyser smart switch installed - heating is the biggest draw on batteries so timing it for the day will go a long way.

I too have a 12kW single-phase Sunsynk inverter (same as Deye) inverter, with 20kWh batteries, and can concur with @mzezman that such an system would be "solid"

1 hour ago, NR7 said:

• 10 x JA 605w bifacial N-type Topconn panels on a section of zinc roof that 345 degrees NNW on two MPPTs (5 panels each).

• 5 x JA 605w bifacial N-type Topconn panels on a section of zinc roof that is 75 degrees ENE. Would sadly be affected by a neighbour's large tree till around 8am (nope, owner won't trim it).

I would recommend that you install strings of 7-8 panels each where roof space allow. PV panels are the single cheapest components of your system, and you would be wise to over-size a bit, for the following reasons:

• Your best solar harvest will theoretically be obtained from panels facing true north, and any deviation to east or west will reduce the efficiency of the panels. Also, you do not state the vertical angle of your roof, and if that is also sub-par your panel yield will be further reduced, so don't do your calculations based on the maximum yield available at optimum angles. Regardless of this, the MPPTs have minimum "start-up" voltages of around 125V - 150V, and if you only have 5 panels per string that minimum start-up voltage will be reached later in the day than if you used 7, or 8 (still safe depending on the brand and model of panels installed) panels per string, and the harvest potential is inverted in the late afternoons when 5 panels will reach the same "shut-off" minimum voltage earlier than a string of 7-8 panels. This alone will increase your daily production quite a bit.

• You should design your system using minimum predicted harvest figures, not max or average - thus what you will be able to harvest in June or July. based on our changing weather patterns observed during the past months, it is quite possible that we will see more cloudy days than what was historically recorded, and that obviously makes correct planning even more crucial. Again, more panels can mean the difference between using grid power (or going to bed earlier...) and remaining comfortably within your planned consumption split when you hit a 3-day rain front where your harvest is reduced by 60% - 80% as happened to me during the past couple of months.

• Even a small amount of shade can reduce your solar harvest from a whole string by 50%, or even more, and more panels on all three strings will lessen this impact substantially.

• Most importantly (and often overlooked) is that you must combine the house consumption during the day (and work on surviving for at least two days of bad weather with say 50% PV yield and 50% battery assist...) with 2 days of battery discharging through the night - thus average10kWh of PV and 18kWh of battery usage, to be re-charged on the third day with good sunshine - thus 28kWh to cover your "normal" daily load plus recharging your rather depleted batteries...

  2 hours ago, NR7 said:

  A neighbor with solar+gas also suggested switching the electric stove over to a gas 5 plate stove, with an electric oven that could then run on the inverter. But I must admit that I am a bit apprehensive about copper gas pipes running in the kitchen to an outdoor bottle which involves a significant length of piping and the cost would mean one less battery.

I did exactly that about 10 years ago, and I have not had a single problem with my system - just make sure that you use a reputable professional to do the installation. Having said that, however, I would not sacrifice the second battery, so rather buy your wife a slow cooker 😁

Lastly, and just my own opinion - the Deye / Sunsynk brand is a reasonable mid-level brand, and although I am not very unhappy with my system, I would rather choose a Tier 1 brand (such as Solis) if I had to start again, especially since they have dropped their prices - something like this:

Solis S6 12kW Single Phase Low Voltage Hybrid Inverter (S6-EH1P12K03-NV-YD-L) 10 Year Warranty With Display

Power Forum Renewable Energy Store | By Powerforum.co.za

R 34,672.50

Posted a similar time to you and looking at a similar set up it seems - I guess I should be deciding between an 8kw and 12kw inverter now.

I haven't had solar but I have had gas in my last 3 homes - one was fortunately municipal/building piped gas, the second was the set up you describe with a bottle outside and then I have also had the set up where the gas bottle is in a vented kitchen cupboard. All have worked really well, with no issues (save for the gas running out while cooking) and I actually prefer cooking on a gas hob than an electric.

8 hours ago, Koch903 said:

I haven't had solar but I have had gas in my last 3 homes

Once you invest in solar, you want to maximise use of the solar system under normal conditions: use it for the geyser, cooking, etc. I like induction plates because they are very responsive.

When the grid is out, you want to minimise draining batteries and then gas heating comes in handy. I use a Cadac cylinder if needed. I doubt if gas heating beats electrical heating on a price basis.

1 hour ago, frivan said:

Once you invest in solar, you want to maximise use of the solar system under normal conditions: use it for the geyser, cooking, etc. I like induction plates because they are very responsive.

When the grid is out, you want to minimise draining batteries and then gas heating comes in handy. I use a Cadac cylinder if needed. I doubt if gas heating beats electrical heating on a price basis.

Agreed on both points that @frivan made. Our stove is a dual 4 gas + 2 electrical plates, with an electric oven. It took a bit of training, but we now run the oven and two electric hobs during the day (obviously only if there is sufficient sun), and the gas burners at night and/or when it's cloudy.

As for wanting to maximize use of solar (don't laugh...) I installed two air conditioners just to "use up" solar power that would otherwise have been wasted 😁

Thanks for all the info guys.

Will see how many panels can fit as we are definitely limited by roof space.

I was previously advised that you can't have panels on the same string in different directions due to shading so I imagine the below is impossible?
It would be the only way to get to 7 panels per string instead of the 6 in the second image.

Edited May 27May 27 by NR7

41 minutes ago, NR7 said:

I was previously advised that you can't have panels on the same string in different directions due to shading so I imagine the below is impossible?
It would be the only way to get to 7 panels per string instead of the 6 in the second image.

I take it the yellow is east?

If you cannot fit more than 6 panels per MPPT per direction (or 2 x 6 facing north if I understand your sketch correctly), then stick to the 6 panels per string - it is not advisable to have panels facing different directions on one MPPT. You can, of course, go for the modern, high-wattage panels... 6 x 620W panels would yield just slightly less than my 7 x 575W panels, and for just a bit more I see that the Power Forum Store currently lists two brands of 635W panels...

59 minutes ago, NR7 said:

Thanks for all the info guys.

Will see how many panels can fit as we are definitely limited by roof space.

I was previously advised that you can't have panels on the same string in different directions due to shading so I imagine the below is impossible?
It would be the only way to get to 7 panels per string instead of the 6 in the second image.

If you are keen on fitting panels to the South-West roof, even if it's sub-optimal, bear in mind that the 12kW inverter has got three MPPT's, which can also take parallel strings. You could therefore combine your orange and red strings onto the first MPPT, two six-strings in parallel, leaving an MPPT free for the South-West side. Maybe you might struggle to fit at least 4 of the 600W panels, but if you could say fit 4, but better 5 of the 450W panels to MPPT3 facing SW, that could plausibly work.