Hi all, I’m a noob when it comes to inverters and solar etc, however I think I need to finally take the plunge and get a system in place. Not sure if there is a sticky thread here to help beginners, as this is my first post.

I’ve done a bit of reading here and there, however still need some guidance.

Currently living in a house, just the wife and myself for now. We have 3 phase power with surge protection, 2 geysers (we only use one, with a geyserwise timer, whilst the other we switch on only when we have guests), gas stove, 2 electric ovens, 3 aircons, dishwasher, washing machine, swimming pool, double garage, electric fence, 90% of lights LED etc.

Average electricity usage is around 600kwh per month, with a bill around R2000 pm (of which half is just fixed costs from CoJ)

Looking at a solar hybrid inverter system, however I don’t want to go overkill and be totally off-grid. Basically want to be able to run the following for 5 hours plus:

Fridge and freezer, lights, TV, amp and sound system with sub, gaming pc, fibre router and ont, cctv system, alarm, fence.

The router & ont, alarm, garage doors and fence already have their own batteries and UPS, however if they can run off the entire system, why not.

The geysers, aircons, oven, pool pump, dishwasher, washing machine I would deem non-essential. Stovetop is gas, and kettle I can use gas. Not sure whether inverters and batteries can handle microwaves and airfryers, but I can get by if needs be.

I need some guidance/confirmation on the following, for my understanding:

• 1.       I have 3 phase power, so will I need to get a 3 phase inverter? I was told that I don’t need to, and that I just need to re-wire my board to get my essentials on a single phase and the non- essentials running between the other 2.

• 2.       Will it be better to convert to single phase? How complicated and costly is this, and does CoJ need to get involved and does my meter need to change?

• 3.       Is it better to have two actual DB boards, one essential and one non-essential, or can the inverter just be hooked up to the relevant breakers individually?

• 4.       There is a big cost difference between Sunsynk and Victron, and I’ve heard that Victron is the best. Is there a tangible difference that justifies the price?

• 5.       I see some inverters are 12v, some 24v and other 48v+. I assume the higher power requirements demand higher voltage for lower resistance/current and more stable operation?

• 6.       Would 5kva be fine for my needs above, or is it better to invest in 8kva?

• 7.       Whilst the batteries are meant to power essential loads, can the solar system still feed power and apply savings to the other non-essential phases/loads during the day? Or will a full 3-phase inverter be required for this?

• 8.       Maybe a dumb question, but when running on batteries during the day, can the system still charge the batteries whilst they are being used to power my appliances, and thus drain them at a lower rate?

• 9.       I previously assumed that all that matters for batteries are the AH rating for capacity and voltage. I realise now that batteries are also rated for kw, and I should also look for discharge rates of 1C for full power delivery. So I assume for a 5 to 5.5kva system I would need a 5kw battery at 1C? And as I go up the inverter ladder (8kva) I would need batteries that deliver more, and thus cost significantly more?

• 10.   What battery capacities should I be looking at for my needs for 5hrs? 100ah, 200ah?

• 11.   Whilst I won’t plan on using the dishwasher and washing machine during loadshedding, would the above system be able to handle running them if they have already started their cycle and there is a power failure?

• 12.   How many panels are suggested for a 5kva - 8kva system.

• 13.   Considering whether to mount the solar on my roof (tile) or garage (IBR). Any advantages or disadvantages? I prefer the garage, as the inverter and batteries can also be stored there, and have a suspicion that the garage gets more sun.

• 14.   How does one determine best location in terms of direct sun? Can I determine this easily or does an installer need to measure this with specialized equipment? I notice the Sun’s path/angle varies between summer and winter.

• 15.   Based on experience, are most of the electricity savings achieved by solar in the day, or by running off batteries in the evening?

• 16.   Are there any households that have fed back to the grid to achieve savings, or is this legislation still miles away?

• 17.   Battery recommendations? Hubble?

That’s about all for now, sorry if they seem like dumb questions, just want to get my facts right before going ahead and don’t want to be ripped off by an installer.

Appreciate your feedback J

 

Hi Sam, Welcome to the Solar world. Many will add to this list of answers. I will answer what I can & leave the remaining to better equipped minds. 

1) Correct. 3 phase inverters are more costly, hence an essentials phase is smart idea for your pocket. Unless you actually have a 3 phase appliance then this makes sense to get a Single phase inverter & DB essentials conversion. 

2) explained above in a sense or you can converter to Single phase it's much more affordable. Not sure how it affects your Eskom supply & how they will bill you etc. Maybe someone better equipped can answer about this process. 

3) the essentials & non is always necessary especially if you install a smaller inverter capacity. Because an entire home cannot fit onto 5kW inverter supply. The split ensures that you don't have the geyser on your backup load supply & drain your battery etc. 

4) Horses for course. Victron is nice, but it's architecture means it's modular & the different components cost a lot. It is an established brand that made its name in the marine boating world where reliably is imperative. 

5) Spot on. Power = Volts x Amps. The whole thing is a garden hose. Think of Amps as water & the cable thickness as hosepipe diameter. You need high amps for smaller voltages. Meaning thick cable. The 48V seems to be the almost sweet spot within reason for most homes of 5kW & and above. Actually this will change with the advent of High Voltage inverters that will hit the market sooner than later. Copper is expensive, higher voltage means much thinner cables. 

6) 5kW is manageable. But requires some babysitting. Wife has the hairdryer on & you boil the kettle. 8kW is more mature more margin but more $$$.

7) A Sunsynk/ Deye inverter can do that. There are 3 phase & single phase versions. In the case of the single phase it will push onto a single phase only. 

😎 depends on the PV solar Array size. Remember the PV array will carry the load & charge the battery. You can setup what priority of these two you most want & the Solar Array will do accordingly. On a sunny day you have more margin to fit in both. 

9) Correct. 1C battery's are more pricey. If you have a 5kW inverter you always try to pair up 1:1 so 5kWh Battery rating is appropriate. But as you grow in size this C rating becomes less important, however, try to keep your peak kW draw correctly sized for the battery C rating. Otherwise you planning to fail & the battery & or inverter can trip. Plan well & know what battery does what before you buy. 

10) depends on your discipline & budget. More is always better. 

11) theoretically yes. Surge or start up motor loads can peak higher for the odd split second. Once started yes this will help to avoid peaks. 

12) depends on your usage. I think 4kW is plenty power in both cases. 

13) there are solar roof mounts for both. Keep the cables as short as possible. Will help your pocket & avoid unnecessary losses in resistance. 

14) We live in the Southern hemisphere, ( I assume you live here in SA) then we need to face north towards the equator. The best Angie depends on your location latitude. In JNB we 26°S so that means the best Angie is that. However, most ppl can't change their roof angle. It is what it is. No specialist equipment. Just don't face panels South, this is criminal. East & west also good in summer, not so good in winter. 

15) Combination of both if you have lithium batteries. 

16) in Cape town yes. In JNB no point they give you a fat Egg 😂

17) My opinion: FreedomWon. Bulletproof for years. They here in SA & will be around the next 10yrs. 

18) I'm an installer. I have seen too many dodgy jobs to mention. I have had to fix too many messes. If you will invest R100k + do your homework, ask around, get references, phone those ppl. Ask how does he/ she respond to after sales support. Don't burn your fingers. Sign a legal agreement with the installer. Unfortunately not many take pride period. 

No such thing as a dumb question. Solar is too broad for us to all know the same things. All the best with your search & please post pics post installation 💡🍺

NB! I missed a lot of errors when I first posted this. If you read it before 10:27 on Nov 30th, please read again to get the proof read version
 

11 hours ago, sam_i_am said:

3.       Is it better to have two actual DB boards, one essential and one non-essential, or can the inverter just be hooked up to the relevant breakers individually?

At install time, an electrician should split the DB. You will see it as one DB, in the same place, from the outside, but internally the wiring will have been split into essential and non-essential loads. The essentials are what you want backed up during an outage.
 

11 hours ago, sam_i_am said:

6.       Would 5kva be fine for my needs above, or is it better to invest in 8kva

Get the 8 if you. Why do I say this? I have a system that pushes out 20A, thus 4,600 W, on the backed up side. That limit can be exceeded for short (10 second) bursts. It sounds like a lot, but it's not really enough. Turn on the kettle, the toaster and the microwave to fix breakfast and watch what happens. 

I didn't understand the implications of this limit when I bought my system. We've learned to live with it, but the extra head room of an 8kW would make life a little easier on the odd occasion.
 

11 hours ago, sam_i_am said:

• 7.       Whilst the batteries are meant to power essential loads, can the solar system still feed power and apply savings to the other non-essential phases/loads during the day? Or will a full 3-phase inverter be required for this?

   

• 8.       Maybe a dumb question, but when running on batteries during the day, can the system still charge the batteries whilst they are being used to power my appliances, and thus drain them at a lower rate?

Let's look at what my system did a few days ago. NB! I have a single phase set up, but I think this will still give you some information.

In this diagram the green line is the battery SOC. The blue line is PV. The yellow line is the load (the demand for power). The purple line is the battery - above the horizontal axis means it's discharging, below means it is charging.


So from left to right

• Overnight the house is just ticking over and the battery slowly discharges.
• At 6:00 the heat pump turns on, and you can see the battery meeting the demand.
• The first PV happens about 6:00, and it starts getting into useful territory about 7:00 (note I have half my panels facing East)
• From about 7:00 the battery is now charging. Demand from the house is still low, and in fact as long as available PV exceeds load the battery will charge.
• 9:45 ish the battery is recharged. Now you see PV drop off and it starts following the load
• Round about 12:00, for a short while, load > PV and so the battery starts discharging.
• But the demand soon drops off, the system pulls as much PV as it can, and the battery recovers.
• Now we are back to PV just supplying the load. At 14:30 the pool pump turns off and PV drops even lower.
• About 16:00 the house starts running off of battery again.

So what I'm trying to show is that most modern systems will charge the batteries AND power the appliances etc. given that there is sufficient PV. On my system, if the PV drops off, then less charge goes to the battery. And if available PV < load then the short fall is drawn from the battery.

Note a big, sustained increase in load about 10:00. That's the pool pump. It's not on the essential side of the DB, but the inverter will still send PV it's way, if there is enough PV.

You will have various settings available on whichever inverter you purchase. You use these to tune your system. In my case I have a rule that says if there is grid, the battery cannot discharge below 40%. So if PV is low, I won't (can't) run my battery into the ground and will always have some in hand in case of an outage.

You should get a similar monitoring tool. Watch it, see how your system reacts, think about how you can tweak your system and tweak your habits.

 

11 hours ago, sam_i_am said:

10.   What battery capacities should I be looking at for my needs for 5hrs? 100ah, 200ah?

I have a 200ah battery. Look at that picture again. Normally after my heat pump has run in the morning I have SOC mid 60s. So I've used about 35 to 40%, IE 4 kWh over night. If I had a 100aH battery, I'd be very close to the end of the useful battery capacity. They usually don't allow themselves to be run all the way down, so you usually have a useful 90% of the actual capacity. With 100aH I'm getting close to that 90% being used and if the sun don't shine and there's load shedding at 6 or even 8, I am going to be skating on very thin ice. With 200aH I can tough it out a lot longer.

Plus if you have 200aH of 1C battery, and an inverter that can handle that amount of current, you can withstand quite large momentary power demands.

Remember that unless you set your system up that way, the battery may not be 100% full when the outage starts. I can run my system in a mode in which it maintains the battery at 100% SOC and waits for an outage. Essentially a huge UPS. But then it would consume grid when PV < Load (so definitely over night). I get better savings letting the system manage itself and making the odd intervention on a day with gloomy weather and load shedding on the horizon.
 

 

11 hours ago, sam_i_am said:

17.   Battery recommendations? Hubble?

I like Freedom Won. It's not the cheapest, but sometimes you get what you pay for. I used to use another brand (not Hubble) and the system was never quite stable. Since the Freedom Won was installed the system has been far more reliable and stable.

Look at the COMBINATION of battery and inverter. Not all batteries get on with all inverters. EG if you buy Revov, they really only promise compatibility with Victron and Sunsynk. You want to be able to run a data connection between the BMS and the inverter so that the BMS tells the inverter what it needs, rather than the BMS having to guestimate.

In the case of my Freedom Won and brand-we-won't-mention: BWWM required a lot of fiddling with settings and it was never an entirely happy relationship. In the case of the FW the technician set my inverter to "default lithium", plugged in the comms cable and within seconds the FW had updated all the necessary settings on the inverter, and now the battery tail wags the inverter dog (and I can't override those settings. The FW will just set everything back the way it wants them.)

I'm not saying that the Freedom Won is the only battery that can do this (I only have experience with two brands of battery), but having that sort of compatibility and intelligent communication between battery and inverter makes life a lot easier and gives your battery the best chance of getting what it needs.

Edited November 30, 20223 yr by Bobster.
didn't proof read

Thanks so much to @Steve87 and @Bobster.. Clarified a lot of my concerns. And its nice to see the practical demonstration of your system Bob, and thanks for the advice on 8kw,  think that would be the minimum to go with then. 

@Bobster.what monitoring tool / software is that? Did it come standard with your inverter?

I think the biggest headache for me will be the 3 phase issue - my electrician for some reason is very hesitant to convert from 3 phase to single phase and is making a big deal out of it. Maybe time to change my electrician 😆. Unfortunately I have no idea of the ramifications of converting down and the cost thereof. 

If I understand correctly, it seems if I stick with a single phase inverter with my current 3 phase grid setup, then the benefit of the solar PV feeding the non-essentials during the day will be lost, as it will only deal with the essential phase items. Converting to single phase, the benefit can be applied to both the essentials (battery connected) and non-essentials (not battery connected, but savings through PV)

The other option would be to just go the 3 phase route and get a 12kw like this ( https://www.inverter-warehouse.co.za/products/deye-12kw-3-phase-hybrid-inverter ) , but then I may just be throwing money away, since a 8kw single phase is about 30% cheaper

           a) On 3 phase systems, are the phases split 4kw each, or will the 12kw be available for all and the power distributed based on load of each phase?

           b) Are the install costs on a 3 phase system significantly higher?

           c) Is the power draw of operating the actual inverter itself much higher on the 3 phase ones?

Edited November 30, 20223 yr by sam_i_am

4 minutes ago, sam_i_am said:

what monitoring tool / software is that? Did it come standard with your inverter?

Yes it did. I have a Goodwe inverter. This uploads data to the Goodwe portal every 5 minutes, and either myself or the installer can view the charts produced from that data.

I suspect the installer may be able to see a bit more than I can, and Goodwe themselves can push firmware updates onto the inverter.

When I was buying I ended up with a choice between Victron and Goodwe, and in both cases I was shown screen shots of the on-line monitoring tools, so I don't think Goodwe are the only guys doing this.

It's a nice to have from the POV of bragging "I've got solar! Wanna see?". It's actually quite important for learning how your system is performing and when you use electricity.