jykenmynie

Hi Danny
Do you have the 8kVA Quatrro?
For Victron, you will have an MPPT charge controller that you connect your solar to. I’m pretty sure you can add as many as you like.
The 8kVA is just the maximum amount you can invert. So basically, take from DC to AC (or AC to DC). But on the DC side, you should be able to happily charge as much as you want.
As an example, assume you have the momentary potential to generate 10kW with your PV. Your house’ demand at that moment 6kW and your batteries are 50% full. Then of the 10kW, 6kW will be inverted and used in the house and the remainder would charge your batteries.
If your batteries are already full, you would only invert the 6 and the other 4 would be “wasted”.
Regarding adding additional batteries: My advice (for what it is worth) would be definitely to add more, like you intend. The 2xUS3000 is technically under spec for just a 5kVA inverter. For your 8kVA inverter, they will struggle to meet even just half the demand when you are getting close to your 8kVA inverting capacity.

My advice would be to sit down with a good installer, work through your exact back up needs and statistics about the weather in your region. Then you get an idea about the battery bank you are looking for.
I’d say that you probably don’t need to go all out on the batteries and just get a generator for the few really bad days in the year.
Remember to take into account battery capacity degradation and DC to AC conversion losses when sizing the bank. You don’t want to go just on the rims from the get go, because your capacity might decline in a few years to the point where it doesn’t meet your needs anymore. 
PV is the cheapest item here, so see how much you can overspec it. Also don’t just go north. Try east and west also for early morning and late afternoon sun. You want to limit your reliance on batteries as much as possible.

Obviously Victron’s MP and Quattro inverters are also “hybrid”. Yes, when appliances that are directly connected to the grid requires power, they would create a demand for it, which something like an energy meter reports to the inverter. The hybrid then knows how much power it can essentially send upstream to try and “zero” the energy meter.
This is obviously great for fully utilising all the PV you have, but not going through the expensive of purchasing 15kVA worth of inverters to run your entire house through, unless you actually need to be off-grid, then a hybrid won’t help.
It does require you to think just a little more about sizing and managing your battery bank, because the inverter would try to zero the energy meter with batteries as well as PV. It would still stop discharging the batteries at a minimum SoC level (unless there is loadshedding, when it’ll take it deeper to keep the critical loads alive). So turning on your oven when there isn’t enough PV would attempt to take the power from the grid, which it will at first, but then the inverter would pick it up from the battery bank.
Obviously the inverter still has a hard limit on inverting capacity, so if you have 10kW of PV available and 10kW of demand, and the batteries are full, it’ll still only take 5kW and invert it to AC (getting say 4.5kW AC). The rest would still go to waste. This situation is typically not possible anyways, because the built-in MPPTs of most inverters aren’t big enough. With a Victron though, you can add what you want on the DC side and therefore create “excess” PV if you need it for a cloudy day, for example, because the entire system is modular.
Essentially, a true “hybrid” is able to bled power sources and push back to the grid (either only to the rest of your house or beyond, depending on settings). It doesn’t need all its power from one source at a time (like PV only, battery only or grid only) and can utilise excess PV much better. You can run your geysers and washing room from PV during the day, for example, even though they are not on your backup circuit.

So, on a good day, like yesterday, I generated 17kWh on the DC side, from my panels. I have 12*320 = 3,840W worth of mono panels. I had maybe another 1kWh I could've used, as the panels idled a little from 16:00 to 18:00 (and my panels are west facing, so I still have some power then). But I think I am pretty much maxed out on 18kWh. So the investment in my panels was about R60k, MPPTs and installation included. CoCT rates on the electricity used after 600kWh for the month, is R2.53 per kWh. So I calculate my ROI on that since my panels keep me out of that range (it is an overestimate on my ROI, but I use it as a "best case" calculation).
Therefore, I can save R45.54 * 90% per day on the AC side, on the best day. So I'll rate that down by 50% (prudently) for bad PV days, but also four out of the three weeks days where I probably won't get to utilise all the available PV. After a year of monitoring my system, I'll have better data to do an actual calculation.
That puts me on about R20.5 per day of savings, or R7,485 per year. Again, assuming Eskom increases in line with investment return earn on the R60k outlay elsewhere (prudently), I shall pay back my investment in about 8 years. BUT WAIT! You say. What about the inverter and the batteries? To me, backup power was a luxury purchase that requires to ROI but my convenience in having power. So it is excluded from my calculations. With an inverter and batteries thrown into the mix, my payback period (as I went Victron and spent R22.5k + R4.5k on the inverter and Venus GX as well as about R45k on the batteries) would be much longer than I expect my batteries to last. But that was never part of my justification for the panels or the purchase of backup power to begin with.

Obviously Victron’s MP and Quattro inverters are also “hybrid”. Yes, when appliances that are directly connected to the grid requires power, they would create a demand for it, which something like an energy meter reports to the inverter. The hybrid then knows how much power it can essentially send upstream to try and “zero” the energy meter.
This is obviously great for fully utilising all the PV you have, but not going through the expensive of purchasing 15kVA worth of inverters to run your entire house through, unless you actually need to be off-grid, then a hybrid won’t help.
It does require you to think just a little more about sizing and managing your battery bank, because the inverter would try to zero the energy meter with batteries as well as PV. It would still stop discharging the batteries at a minimum SoC level (unless there is loadshedding, when it’ll take it deeper to keep the critical loads alive). So turning on your oven when there isn’t enough PV would attempt to take the power from the grid, which it will at first, but then the inverter would pick it up from the battery bank.
Obviously the inverter still has a hard limit on inverting capacity, so if you have 10kW of PV available and 10kW of demand, and the batteries are full, it’ll still only take 5kW and invert it to AC (getting say 4.5kW AC). The rest would still go to waste. This situation is typically not possible anyways, because the built-in MPPTs of most inverters aren’t big enough. With a Victron though, you can add what you want on the DC side and therefore create “excess” PV if you need it for a cloudy day, for example, because the entire system is modular.
Essentially, a true “hybrid” is able to bled power sources and push back to the grid (either only to the rest of your house or beyond, depending on settings). It doesn’t need all its power from one source at a time (like PV only, battery only or grid only) and can utilise excess PV much better. You can run your geysers and washing room from PV during the day, for example, even though they are not on your backup circuit.

So, on a good day, like yesterday, I generated 17kWh on the DC side, from my panels. I have 12*320 = 3,840W worth of mono panels. I had maybe another 1kWh I could've used, as the panels idled a little from 16:00 to 18:00 (and my panels are west facing, so I still have some power then). But I think I am pretty much maxed out on 18kWh. So the investment in my panels was about R60k, MPPTs and installation included. CoCT rates on the electricity used after 600kWh for the month, is R2.53 per kWh. So I calculate my ROI on that since my panels keep me out of that range (it is an overestimate on my ROI, but I use it as a "best case" calculation).
Therefore, I can save R45.54 * 90% per day on the AC side, on the best day. So I'll rate that down by 50% (prudently) for bad PV days, but also four out of the three weeks days where I probably won't get to utilise all the available PV. After a year of monitoring my system, I'll have better data to do an actual calculation.
That puts me on about R20.5 per day of savings, or R7,485 per year. Again, assuming Eskom increases in line with investment return earn on the R60k outlay elsewhere (prudently), I shall pay back my investment in about 8 years. BUT WAIT! You say. What about the inverter and the batteries? To me, backup power was a luxury purchase that requires to ROI but my convenience in having power. So it is excluded from my calculations. With an inverter and batteries thrown into the mix, my payback period (as I went Victron and spent R22.5k + R4.5k on the inverter and Venus GX as well as about R45k on the batteries) would be much longer than I expect my batteries to last. But that was never part of my justification for the panels or the purchase of backup power to begin with.

So, on a good day, like yesterday, I generated 17kWh on the DC side, from my panels. I have 12*320 = 3,840W worth of mono panels. I had maybe another 1kWh I could've used, as the panels idled a little from 16:00 to 18:00 (and my panels are west facing, so I still have some power then). But I think I am pretty much maxed out on 18kWh. So the investment in my panels was about R60k, MPPTs and installation included. CoCT rates on the electricity used after 600kWh for the month, is R2.53 per kWh. So I calculate my ROI on that since my panels keep me out of that range (it is an overestimate on my ROI, but I use it as a "best case" calculation).
Therefore, I can save R45.54 * 90% per day on the AC side, on the best day. So I'll rate that down by 50% (prudently) for bad PV days, but also four out of the three weeks days where I probably won't get to utilise all the available PV. After a year of monitoring my system, I'll have better data to do an actual calculation.
That puts me on about R20.5 per day of savings, or R7,485 per year. Again, assuming Eskom increases in line with investment return earn on the R60k outlay elsewhere (prudently), I shall pay back my investment in about 8 years. BUT WAIT! You say. What about the inverter and the batteries? To me, backup power was a luxury purchase that requires to ROI but my convenience in having power. So it is excluded from my calculations. With an inverter and batteries thrown into the mix, my payback period (as I went Victron and spent R22.5k + R4.5k on the inverter and Venus GX as well as about R45k on the batteries) would be much longer than I expect my batteries to last. But that was never part of my justification for the panels or the purchase of backup power to begin with.

For me, Victron has nothing to do with pride. You are building a system with presumably R60k+ worth of batteries and R30k+ of panels. Maybe another R10k for DBs and a bit of wiring. Now decide what inverter you want. I can go on and on about why I think Victron is an amazing product, with brilliant support, flexibility and reliability. However, I could also say:
You probably want to go solar because you are sick and tired of Eskom’s unreliability. In that case, you probably want to replace Eskom with something reliable.

Not sure how to R1.3/kWh.
Think they rate it for 6000 cycles with 60% capacity remaining at 80% DoD, you can assume linear degradation of capacity for simplicity. And DC to AC conversion has about 10% loss. So:
6,000 * [(1 - 0.6)/2] * 0.8 * 3.5 * (1 - 0.1) = 12,096 kWh usable on the AC side. The battery costs about R23.5k, so R1.94 per kWh. Pretty much in line with CoCT tarrifs.
Batteries are only useful up to the point where they make your system viable (the inverter would be able to function normally) or if you are completely off-grid. Unless Eskom increases rates by most than the investment return you would earn elsewhere.
If you have spare cash, I think this is more effectively invested in stuff like a heat pump for your geyser (when you don't have solar power it still saves money), LED lights, more energy efficient appliances, etc.

Müller was a bit like a furniture store back in the 1900s in Cape Town. If my google-fu has not left me, the remains of that company is still around via Allen and Fisher pianos, who still have premises in Wynberg today. They imported pianos from Germany and sold them under their "house brand". That is why many of these pianos are basically either an Otto Bach or a Carl/Carol Otto under the skin. Some of them are quite good. Others (like mine) look the part but are basically workhorses underneath. After buying such a piano without doing any of the required research (and almost ending up with a dud, but we saved it), I did the work afterwards. That's when you discover how the styling changed over the years. Simply things like "stalactites" (pretty hanging wood carvings under the keyboard) died out in the early 1900s, so if you see that, you know it is very old. Until the 1930s, you usually didn't have legs under the keyboard. Fluting (you'll have to look that up I think) was common from 1900 to around 1925. Overdamper (where the damper is above the hammer) was more common in the late 1800s, but by 1910 pretty much everyone is making underdamper pianos. And so on and so forth...
The you get to the interesting time when better materials get into it. Using an aluminium rail in the action (the action is the part with the hammers) was a significant improvement from what came before.
Of course things also went the other way. Good pianos have a Sound board made of spruce. Cheap ones... use a cheaper wood, but then they laminate it with spruce to make it look good... 🙂
So... yeah there was this story about a guy who went to a fight and then a hockey game broke out... well, we started with batteries, and then I went completely OT. I hope everyone had a good read 🙂
 

Okay, I’m talking to my mom this weekend about the maintenance of that piano! Jeez, can’t let an heirloom go to waste. It was the piano on which the four generations since my great grandmother was taught.
If I recall correctly it is also a Müller, but I have never tried to trace its origin. I remember that the old blind German tuned that came to house to tune it always wanted to buy it afterwards, doubt he will still want to do that now...
Ah, a good way to start my day with positivity! 😅

I bought myself a Clavinova CVP-401 second hand for about R10k when I started working. Yeah, it doesn't have the same character as an actual upright (not even considering a baby grand, let alone actual grand). However, having moved a lot, the Clavinova is a much better travel partner, no going out of tuning! It has a pretty natural feel due to the weighted keys and a good sound. And then there is the added fun you can have with it - Although I rarely did as I'm pretty much happy with just classic piano music. Recently, I started playing much more up beat stuff... Whatever seems to make my baby daughter happy, more Old McDonald, less Chopin or Debussy!
When my mom moves to a smaller place, I'll see if I can convince my siblings that I should get the upright. Really nice, ivory caps on the notes and rose wood inlays (though two caps flew off after a few bouts of glissandos - which also put a to such abusive playstyles). But it needs A LOT of work. My mom hasn't been keeping it tuned or serviced...

Get an installer to do a site inspection. I received a quote for full installation (everything that is required - excluding a geyser of course, I have one) and a 4.7kW ITS heatpump for about R25k. Keep in mind that, while this is close to the price of one battery, it will actually save you more money (and off-grid battery time) than a 3.5kWh battery will. That battery will be empty after an hour of running your 3kW element. Then you won't yet have enough hot water (obviously depending on how much water you use, but you mentioned 2 hours of running). The heatpump would use about:
6kWh / 4.7kW ~= 80 minutes @ 1.17kW ~= 1.5kW.
So you just saved 4.5kWh (that is 1.6 US3000B batteries if you discharge them 80%). My above calculation have quite a bit of margin for error in before it is equivalent to one battery only. Also, when the sun isn't shinning, a heatpump would still save you money while your batteries won't be able to be charged properly with the available PV.

So the "rule of thumb" as I have it, is 1kWh per 1kVA your inverter can invert. So 10kWh for you. However, Pylontech's BMS has some more restrictive discharge current allowances. So the way I have it is that for my 5kVA MP II, I should really run 3xUS3000B. So for you, 6 would probably be optimal. I'm not an expert on these items, so I'd rather wait until someone more knowledgeable replies.
Agreed, so both of those are "luxury" purchases for me - So if you like it and can afford it - Do it!

What really helped me understand my electricity usage patterns is the energy meter I installed with my backup system. First few days I was running around like a mad-man, monitoring what appliances came on and their usage. Now I can basically just look at the time of day and the instantaneous usage and know exactly what is happening in my house, even when I’m not home.
Just with that, I was able to make my wife more energy conscious (I’ve always been very frugal, coming from a farming family where we saved water and electricity like mad) by showing her what it uses and costs (she is very clued up financially, so that wasn’t a difficult conversation).
Just using electricity better already helped a lot, such as:
- Switching off unneeded lights
- Not boiling more water than one needs 
- Not leaving heaters on or using them when extra clothes would do
- Not using the tumble dryer when the sun is out (washing machine is also a biggy if it needs to heat water, similarly dishwasher, but those are less easily optimised)
So then we got PV and shifted our loads. Granted, my current setup is west facing so early in the day it isn’t great, but that would be rectified in the medium term, but still we ended up saving 60+% on our purchases from the grid. I can likely improve upon  that, but not running my batteries below 60% at the moment. This is just due to my PV being somewhat underspecced, so on a good day, I’ll still struggle to meet my day time demands and bring the batteries up from 20% to 100%. We are in the process of adding more PV that would hopefully help with that.
Maybe my story helps you in your quest to save some of those kWhs!

Run it off the grid if you are running it that time. At least that is what I do. Not for it for me to save a few bucks on the one hour of a geyser heating up every day and abusing my batteries like that. I set a scheduled charging slot for my batteries between 05:00 and 07:00 during which time my geyser comes on. The scheduled charge is set to stop at 30% SoC, which is lower than my minimum SoC of 50%, so all that really happens is it prohibits my batteries from being discharged during that morning geyser slot.
Or get a heat pump for your geyser. That might be a better investment than another battery and cost about the same.

@jykenmynie I finally got the aircon hooked up and it is working fine. It is this unit if you want to have a look at the specs.
Will be running it through the week to see what power consumption is like. Although, I live in a converted shipping container (tiny house) so the area to keep cool is much smaller than in a typical houses.

Just remember that no battery would keep its full capacity over its life. IIRC you can expect these batteries to end at around 60% original capacity. So on average:
2.4 * 0.8 (adjustment for average original capacity) * 6,000 * 2.1 = 24,192. You need to compare that against the battery's price. As long as Eskom's price increases are in line with what a risk-free investment would have earned (say keeping your money in your bond), then it future increases would have no impact on this calculation (although you can argue that you have hedged out uncertainty about what those units will cost you, which does have value).
Depending on your municipality, electricity could have a different price and you could also be charged more or less after a certain amount of units.
For me: Buying my batteries (and consequently an inverter) on its own wasn't as much an "investment" in electricity cost savings as it was an "investment" in being able to be hedged against loadshedding. I decided that having the predictability of my evening routine is worth at least something to me. So it was a luxury purchase that require no further justification. Purchasing solar panels was therefore the only cost I need to factor into deciding whether the electricity savings is worth it to me as an "investment".

Just remember that no battery would keep its full capacity over its life. IIRC you can expect these batteries to end at around 60% original capacity. So on average:
2.4 * 0.8 (adjustment for average original capacity) * 6,000 * 2.1 = 24,192. You need to compare that against the battery's price. As long as Eskom's price increases are in line with what a risk-free investment would have earned (say keeping your money in your bond), then it future increases would have no impact on this calculation (although you can argue that you have hedged out uncertainty about what those units will cost you, which does have value).
Depending on your municipality, electricity could have a different price and you could also be charged more or less after a certain amount of units.
For me: Buying my batteries (and consequently an inverter) on its own wasn't as much an "investment" in electricity cost savings as it was an "investment" in being able to be hedged against loadshedding. I decided that having the predictability of my evening routine is worth at least something to me. So it was a luxury purchase that require no further justification. Purchasing solar panels was therefore the only cost I need to factor into deciding whether the electricity savings is worth it to me as an "investment".

I would definitely go with Pylontech, never had a single problem with them, on the other hand I have had nothing but problems with BlueNova.
Not to mention that their so-called 4kWh battery is actually 3.2kWh, but if you ask them about it they claim that they spec. the C10 rating which is ridiculous.
That particular battery you are looking at, which BlueNova claim to be 77Ah has 60Ah cells inside (the capacity is printed on the cells by the manufacturer).

I won’t call lithium “settling”, because it seems to be the best all round option for solar systems at the moment.

Trust me, it's not possible for LiFePo4. With some other Liion yes, but not here.
The only way to determine the correct SoC is counting in/out amphours. So Victron BMV700, shunt, coloumbmeter. And since BMS already has this circuit implemented, the most obvious way is to communicate with the BMS.
But don't worry. I would say that within 5yrs this feature (custom top-bottom charge/discharge based on the true SoC and BMS communication) will make it to the inverters
 
In the meantime, you have to code your own middleware, if you want this.

I think some of it has to do with the canbus communications with the battery. In later discussions, it seems these Growatt inverters work fine with the same  battery, as long as you set the settings in some way, or if there is no comms.
Now this is a field I know a little something about. Some of these managed batteries do current control. They instruct the inverter to charge or disharge by a certain amount. Quite often these batteries will send a zero when they want the inverter to stop completely (eg when the battery is completely full or completely empty), in Victron speak we call that the DCL (discharge current limit) and the CCL (charge current limit).
The DCL=0 case is mostly uncontroversial. Pylontech batteries, for example, send this before the battery is completely empty, and that way it protects itself from very deep discharges and so prolongs the life of the battery.
The more problematic case is when the battery sends CCL=0. Then the kind of toplogy of your inverter, and how your PV is coupled, comes into play.
As one example, imagine an SMA system. All your PV is tied on the AC side, using SunnyBoy grid-tie inverters. Then you have a SunnyIsland inverter connected to the battery. This inverter charges the battery and listens to the CAN-bus BMS on the battery. If the battery says CCL=0, the inverter can do that. It does not affect the delivery of PV at all. That's tied on the other side, flows normally to the loads, and out onto the grid if not limited.
Or consider a Goodwe. The PV connects directly to the high voltage DC bus, in other words even though it is a hybrid, the PV ties onto the grid in a very similar manner to the SMA example above, on the high voltage side. It can take the battery current right down to zero and just leave it there, without affecting PV delivery at all.
But now consider the cases where the PV is DC-tied, which is the case with this Growatt and also with many Victron systems. This is what you could call a "push pull" system. The DC chargers push current into the DC bus (and the batteries), and the inverter takes current from the same. If the load and the PV does not quite match, the remainder naturally comes from the battery.
Now imagine trying to do current control in a setup like this. With a hybrid inverter, some of that is possible. You can mix in some grid power in order to comply with a lower DCL, and you can limit solar chargers to comply with a lower CCL, but the basic problem remains: That in a DC-coupled setup, the battery is an integral part of the power delivery mechanism, and a complete zero situation is never going to happen.
Now I get to my point: I think these troubles start when batteries designed for one kind of ecosystem (the current-control world) is used in the other ecosystem. The battery says CCL=0, and so the inverter stops all charging (throttles the MPPTs to zero), and then the inverter has no choice but to discharge the battery rather than use the PV. After a while, the battery raises the CCL again (since it is now down to 95%) and suddenly the world returns to normal, for a while.
This gives you that little bit of micro-cycling at the top. And of course you don't want that.
The solution is to not do current control, but to adjust the charge voltage of the battery. If you don't want the battery to charge, lowering the charge voltage will stop that. It's as sure as the fact that water cannot run uphill. But that would be the "other" kind of ecosystem I referred to.
Now some inverter makers have workarounds implemented to bridge these little issues. And I assume, Growatt hasn't got there yet.

Have you considered getting a 48V inverter also? Since you do not have a terribly expensive one currently, it might be worthwhile? Not sure about the downsides of 48V compared to 24V.

With most pumps though, the running rating is one thing, but starting it is another. It might draw 5-7 times its running wattage for a few seconds starting up. Most inverters can only surge 2 times their kVA. That pump might ask for 112 - 160 kVA starting up (assuming a power factor of 0.8). You will need a small army of inverters.
It really doesn't seem like an efficient solution.
Even a smaller 10kW pump (let's say 12 kVA) would still ask for 60 - 84 kVA starting. I really think you should rather consider plonkster's suggestion of a dedicated solar pump.