Hi everyone

It seems like 3kw / 5 kw new and used hybrid inverters are fairly cheap ( around R3500 new ) . The batteries though are way to expensive for my objective.

The plan is to only connect a 3kw geyser to one of these hybrid inverters with 4 panels ( 4 X 545W panels ) . No batteries involved due to the cost. I am willing to swop out the geyser element to 2kw if required as that is a cheap DIY.

The main question on my mind before buying any equipment is since the geyser draws 3KW and the solar will obviosuly not come anywhere close to this on an average day will this system :

A) purely only draw from the mains and ignore whatever the PVs are outputting or

B) draw from the PVs and then take the balance required from the mains at the same time - if this is even possible. So if my PVSs give 1KW for argument sake it takes the other 2KW from the mains or

C) use the 1KW of solar PV energy and slowly heat up the geyser

N.B - no battery will be connected to the inverter !

I need the geyser to use hot water from 5.30 to 6.30 AM and then again for another 2 hours or so from 5 to 7. ( this is currently done using a geyser timer but since solar has come down in price I thought let me give this a go if I can set up something for 10 to 12K ). I have done research already on Geysertech, Gas and vacuum/collector plates so this is the last option before deciding what route to go.

Thank you

A) purely only draw from the mains most of the times.

B) will not work.

C) use the 1KW of solar PV energy and slowly heat up the geyser, will also not happen.

5.30 to 6.30 AM no sun.

5 to 7 mostly no sun. Perhaps in summer but most of the time will come of mains.

Set it up as a grid-tied inverter. It will supplement your feed from the grid. So if you are getting 1kW from the panels and the load is 2.5 kW, you will draw 1.5 from the grid. The trick is to run the big loads when the sun is high in the sky. Any modern inverter will give you a monitoring tool so that you can watch it and see how it behaves and learn when it is producing power.

You can add batteries later. If you can charge your battery during the day, then keep the demand low at night then you will start saving a lot more, and you will have protection when there are outages.

Edited November 10, 2025Nov 10 by Bobster.

PS. Splash out and get a few more panels. You know you want to. Better performance on overcast days, and more savings when the sun is shining. Panels don't cost a lot right now.

1 hour ago, Bobster. said:

Set it up as a grid-tied inverter. It will supplement your feed from the grid. So if you are getting 1kW from the panels and the load is 2.5 kW, you will draw 1.5 from the grid. The trick is to run the big loads when the sun is high in the sky. Any modern inverter will give you a monitoring tool so that you can watch it and see how it behaves and learn when it is producing power.

I dont know if that will work. I know about using battery plus solar to supply the load. But if there is no batteries I have never tested to see if an inverter will use both PV and Grid to supply. Works for battery charging yes, but to supply a load? I dont think so. Could be wrong of course.

26 minutes ago, Denns said:

I dont know if that will work. I know about using battery plus solar to supply the load. But if there is no batteries I have never tested to see if an inverter will use both PV and Grid to supply. Works for battery charging yes, but to supply a load? I dont think so. Could be wrong of course.

It will work as explained by @Bobster. - you don't really need batteries to make solar panels work

13 minutes ago, Demo said:

It will work as explained by @Bobster. - you don't really need batteries to make solar panels work

I know you don't need batteries but what happens when the load exceeds the PV coming in? Typically, the inverter will pull from the batteries and PV. Without the batteries and enough solar to supply the entire load, will the DC bus in the inverter be stable enough for it to use it to supply AC from both there and the grid? Are you saying it will pull from both the grid and PV simultaneously? That I have never tried.

Edited November 10, 2025Nov 10 by Denns

18 minutes ago, Denns said:

Are you saying it will pull from both the grid and PV simultaneously?

Yes

56 minutes ago, Denns said:

I know you don't need batteries but what happens when the load exceeds the PV coming in? Typically, the inverter will pull from the batteries and PV. Without the batteries and enough solar to supply the entire load, will the DC bus in the inverter be stable enough for it to use it to supply AC from both there and the grid? Are you saying it will pull from both the grid and PV simultaneously? That I have never tried.

As @Bobster. explained. That is how a string or grid tied works. The real answer is not to put ALL hybrids as per sales talk in the same box. If the hybrid is a Sunsynk or Deye they can operate as pure grid tied units without the battery. Again as said earlier at some stage one would like to run if there is no grid = adding the battery later and use the extra PV generated from the battery. This gives a better ROI if one buys a true hybrid.

Some high voltage MPPTs can also work without grid or battery. Here we are looking at the Kodak which is similar in some aspects to the Axpert high voltage MPPT.

Using a Solis or other string inverter it will use all the PV available and draw only the remaining power from the grid. In this case you do need the grid to synk 1st in order to produce power in phase with the grid. With the Solis it will be the 4G mini range and not the hybrid S6. They cannot work with a battery and is limited in use if ever one want to add batteries you are snookered. However they are very cheap (2nd hand) and ultra reliable. Not much of a market for them as everybody want battery back up.

1 hour ago, Denns said:

I know you don't need batteries but what happens when the load exceeds the PV coming in?

Same thing that happens when my battery is charged, demand is low, and it's sunny. The inverter just draws what it needs from the panels.

Of course all that solar energy has to go somewhere. I'm told the panels heat up, but I can't vouch for it.

Depending on tariffs available to you, feeding in might be an idea you want to explore. Check the tariffs carefully. Look for one off costs (like a 2 way meter).

Feeding back is probably going to involve registering your system. Hmmm... Another cost. Live with the system for a couple of months, try to get a handle on how much you'd have available to feed back in. THEN read the tariffs.

But it's not a problem. Inverters know how to handle this situation. But you want to reduce the occasions on which this happens. Run your geyser midday or early afternoon. Timer switches are your friend. I run the pool pump, the dishwasher, the heatpump during the day. You'll figure out when to run what, how to make the best use of PV.

Batteries unlock maximum savings and give you protection against power cuts. On prepaid in COJ the minimum purchase you can make right now is 55.5 kWh per month. Every month I bank some.

Edited November 10, 2025Nov 10 by Bobster.
Paragraph about registration

14 minutes ago, Bobster. said:

Of course all that solar energy has to go somewhere. I'm told the panels heat up, but I can't vouch for it

Timer switches are your friend. I run the pool pump, the dishwasher, the heatpump during the day. You'll figure out when to run what, how to make the best use of PV.

Batteries unlock maximum savings and give you protection against power cuts. On prepaid in COJ the minimum purchase you can make right now is 55.5 kWh per month. Every month I bank some.

I can say that the panels run at full output based on irradiation. The panels are made to work this way. When I started with by grid tied I only used 2 x 270W panels. Any load switched on used the power from the panels 1st and only the rest from the grid.

When I maxed out my 1.5kW from the 1st inverter I bought a 2nd one with its own string of 3 x 450W panels.

This is bad that COJ has a minimum of units you can buy. We in Tshwane can buy any amount in Rand. Currently I am buying R40 pm and my units are adding up. During the 2 winter months I bought R80 and R120. My grid use has been as low as 4kWh per month before clouds set in during September.

Here are some of my figures. At this time I used about 10 kWh per day. About 3 kWh came from PV and the balance from the grid. If it wasn't for the Solis that had a low 60V start MPPT I would never have gained the experience of using a low budget grid tied system. Paid for itself in less than 3 years.

Edited November 10, 2025Nov 10 by Scorp007

35 minutes ago, Scorp007 said:

This is bad that COJ has a minimum of units you can buy. We in Tshwane can buy any amount in Rand. Currently I am buying R40 pm and my units are adding up.

COJ have quite low costs per kWh, but very high fixed fees on post paid service. Like a grand a month. So folks have been converting to prepaid. Higher per unit costs, but you save on the fixed fees.

2 years ago they introduced a R200 fixed fee on prepaid meters. But you can't just pay the fixed charge. They pro-rata the first few hundred rand so that some goes to the fixed fee & some to units. So you HAVE to buy some units in a month. Right now R400 pays the fixed fee, VAT, and gives you 55.5 units. This is the lesser of evils, so...

But you make my point even better. Batteries means you store PV during the day, use the stored PV at night, and then you start saving.

On 2025/11/10 at 6:24 PM, Bobster. said:

Set it up as a grid-tied inverter. It will supplement your feed from the grid. So if you are getting 1kW from the panels and the load is 2.5 kW, you will draw 1.5 from the grid. The trick is to run the big loads when the sun is high in the sky. Any modern inverter will give you a monitoring tool so that you can watch it and see how it behaves and learn when it is producing power.

You can add batteries later. If you can charge your battery during the day, then keep the demand low at night then you will start saving a lot more, and you will have protection when there are outages.

Thank you, I am leaning towards this @Bobster. now that you suggested it as it could supplement other items running during the day like the fridge etc. I am buying panels so long this weekend just to get started and then will start the process of looking for an inverter. I am getting mixed views regarding hybrid inverters working without a battery ( if I see savings I will definitely buy batteries later on ) . According to your understanding they should work without batteries right ? Dont worry I wont hold you to anything lol but that is how I understand it too since the grid will power the inverter and they solar feeds to the inverter /grid to supplement . Last question since you know what you talking about. What do you think about geyser only options like vacuum tubes / plates. I can only do one option as in solar or geyser so I need to choose wisely and I dont want to go over R15k. It looks like solar heating will avoid messing with the DB and just need a plumber to certify so more simpler but solar/inverter can power the geyser and possibly other stuff as well ( even if I get hypothetically / hopefully get 2kw per day from 3 panels that is about R2500 per year so it will take many years to recoup the outlay. I am just assuming 2Kw in savings since I dont have batteries. The cost of batteries changes the calculation and makes the ROI even worse. Your thoughts?

53 minutes ago, Lucang said:

Thank you, I am leaning towards this @Bobster. now that you suggested it as it could supplement other items running during the day like the fridge etc. I am buying panels so long this weekend just to get started and then will start the process of looking for an inverter. I am getting mixed views regarding hybrid inverters working without a battery ( if I see savings I will definitely buy batteries later on ) . According to your understanding they should work without batteries right ? Dont worry I wont hold you to anything lol but that is how I understand it too since the grid will power the inverter and they solar feeds to the inverter /grid to supplement . Last question since you know what you talking about. What do you think about geyser only options like vacuum tubes / plates. I can only do one option as in solar or geyser so I need to choose wisely and I dont want to go over R15k. It looks like solar heating will avoid messing with the DB and just need a plumber to certify so more simpler but solar/inverter can power the geyser and possibly other stuff as well ( even if I get hypothetically / hopefully get 2kw per day from 3 panels that is about R2500 per year so it will take many years to recoup the outlay. I am just assuming 2Kw in savings since I dont have batteries. The cost of batteries changes the calculation and makes the ROI even worse. Your thoughts?

You can easily get 6kwh per day from 3 x 545W panels provided you have any loads that need power during the sunshine period. Excluding harsh winters in the Cape. My table I placed yesterday was using 3 x 270W panels in Gauteng and that was using all the PV power generated without batteries.

1 hour ago, HowTo said:

A) purely only draw from the mains most of the times.

B) will not work.

C) use the 1KW of solar PV energy and slowly heat up the geyser, will also not happen.

5.30 to 6.30 AM no sun.

5 to 7 mostly no sun. Perhaps in summer but most of the time will come of mains.

2 hours ago, Scorp007 said:

You can easily get 6kwh per day from 3 x 545W panels provided you have any loads that need power during the sunshine period. Excluding harsh winters in the Cape. My table I placed yesterday was using 3 x 270W panels in Gauteng and that was using all the PV power generated without batteries.

@Scorp007 thank you, that is very reassuring, especially the figures you provided yesterday. I think I will just get 2x 545watt panels to start the experiment thus weekend. Do you think those cheap hybrid 3kva inverters are ok to start off with? I can get them for 2.5 almost new snd around 3.5k new. Im really trying to do all for 10k for nw and once I can see the feasibility I will consider batteries

1 hour ago, Lucang said:

@Scorp007 thank you, that is very reassuring, especially the figures you provided yesterday. I think I will just get 2x 545watt panels to start the experiment thus weekend. Do you think those cheap hybrid 3kva inverters are ok to start off with? I can get them for 2.5 almost new snd around 3.5k new. Im really trying to do all for 10k for nw and once I can see the feasibility I will consider batteries

I cannot say these cheap hybrids can switch on without a battery as they are meant to provide power when there is no grid or PV.

The figures provided was using a grid tied=string inverter. The Solis 4g mini in my case. This unit needs grid to operate and then can use PV to generate 230V on top of the grid but power generated is used 1st and the remaining bit of the load comes from grid.

Edited November 12, 2025Nov 12 by Scorp007

8 hours ago, Scorp007 said:

I cannot say these cheap hybrids can switch on without a battery as they are meant to provide power when there is no grid or PV.

The figures provided was using a grid tied=string inverter. The Solis 4g mini in my case. This unit needs grid to operate and then can use PV to generate 230V on top of the grid but power generated is used 1st and the remaining bit of the load comes from grid.

My inverter is a 3.6KW MUST I got for 3.4k. It can run fine without battery and on PV alone.

I unfortunately can’t test his scenario because I don’t have a grid connection to my inverter so I won’t be able to see if it can supplement the excess load with the Grid.

Otherwise when I was busy on the battery side a few months ago with some changes the house ran for half the day off PV alone.

Edited November 13, 2025Nov 13 by Denns

15 hours ago, Lucang said:

I am getting mixed views regarding hybrid inverters working without a battery ( if I see savings I will definitely buy batteries later on ) . According to your understanding they should work without batteries right ?

It depends on the inverter, I think. Modern hybrid inverters can work without batteries, but check the specs to be sure. They are not made for South Africa. They are made for the EU and the USA where grids are reliable but people want to reduce their bill and their carbon footprint. My Goodwe can run without batteries.

A lot of these systems must have grid or battery to work. So it's likely that if you go the grid-tie route you will save money but you won't have any protection against outages.

Load shedding is not much of a problem right now, so a grid-tie system can save you some money. You are right in thinking that the way to maximise it is to run stuff whilst the sun is up and you are generating good power.

Edited November 13, 2025Nov 13 by Bobster.

1 hour ago, Bobster. said:

It depends on the inverter, I think. Modern hybrid inverters can work without batteries, but check the specs to be sure. They are not made for South Africa. They are made for the EU and the USA where grids are reliable but people want to reduce their bill and their carbon footprint. My Goodwe can run without batteries.

A lot of these systems must have grid or battery to work. So it's likely that if you go the grid-tie route you will save money but you won't have any protection against outages.

Load shedding is not much of a problem right now, so a grid-tie system can save you some money. You are right in thinking that the way to maximise it is to run stuff whilst the sun is up and you are generating good power.

If savings are that important to him and he doesnt want to spend on batteries, I recommend he just takes care of the geyser then. There is plently of solutions out there to do it for the 10k he is talking about. If he could strech it to 20k, a HP?