A new user here

I have just had my system switched on for a few days. The only power we have drawn from the grid is the small amount that trickles to the inverter

8kw Solis inverter

3 x solis 5kw batteries

12 x 550w panels.

I have a solar geyser and gas hob which helps a lot with limiting our usage

The installer set of DOD @50%. So far the lowest we have dropped battery backup at night was around 67%. The average has been in the 70s

My question is what will our solar generation output drop dramatically in the winter months in the eastern cape. Based on current output would we still make it on battery backup

I am also on the fence regarding registration with the council. My ideal scenario would be to have the system disconnected and only run our own power produced. I don't want to end up paying a massive fee monthly just to tied to the grid when I am not using the grid. The plan was to run for 12 months and see if we could survive on the current setup without being grid tied before having our supply disconnected. but with Eskom and municipalities threatening fines there is a lot of confusion as a new solar user as what is the best course of action.

Register with the council before end of March and take the plunge and disconnect from the grid or stay on the grid and pay the grid connection fee.

Advice would be appreciated in this matter

59 minutes ago, KAPLF said:

Advice would be appreciated in this matter

There will be an overcast, cold week for which you cannot economically size solar and batteries. Then Eskom or own generation are your options.

At the least you need to run the system through a winter and see how it performs.

And chuck everything at it. I am very close to going off grid, or so I think. But my lawn mower will trip the inverter every time. So I have to resort to trimming the lawn the old fashioned way, or something. Even then I will be close to the limit if the pool & the heatpump are running, the dishwasher is heating and the wife feels like a slice of toast.

Off grid can be achieved, but it may require some sacrifices of investment in more hardware. And you don't have enough data yet.

As @frivan says, plan for bad circumstances. I'm saying that I'm this far away from going off grid, but could I withstand 3 or 4 consecutive overcast days? Hmmmm....

20 hours ago, KAPLF said:

Advice would be appreciated in this matter

I agree with Frivan and Bobster.

You have to monitor and see over time how your system performs. I recently went off-grid and got my meter and cable removed by City Power in JHB. I had run an off-grid installation since March or so last year. I kept making adjustments, such as making the house very efficient. I have a 3.6kW inverter, but fortunately I have not had issues with overloading, etc., even though the Oven and things like Dishwasher etc are on it. I use Tuya to smart manage everything using smart switches, so the chances of overloading are next to none. Gardeners blower and trimmer don't give the inverter any issues and have been running my grinder and drill on it with no problem, also.

With all the power dieting the house went through, I never needed the grid throughout the period. The last month in Joburg and this week in particular has been very bad for generation, and I have never had problems. I don't really monitor the system anymore (I can only monitor consumption via Tuya, I never bought the dongle to monitor the batteries or generation). I have a generator connection, but I have not bought a generator yet. I told myself to only buy one if my kitchen goes out for more than a day due to low SOC on the batteries.

My kitchen is on the non-essential side of the inverter (Microwave, Dishwasher, washing machine, Oven, Air fryer, Toaster, Kettle). Because I have GEL batteries, when the SOC is lower, a big appliance kicking in will dip the voltage on the batteries, and the inverter will automatically kill the kitchen, but the house will remain with power. It has honestly happened to me 3 times if not mistaken, in about a year. And always in the morning. I also have a built-in 4 plate gas hob, so I don't really care when it happens. But the power comes back in an hour or so when the generation starts after 7 in the morning. It hasn't inconvenienced me, and it hasn't happened in August last year, if not mistaken and I have made some more adjustments to the system (added 2 more panels on the inverter and 1 on the charge controller).

It is otherwise very doable to go off-grid. If I managed with a 3.6kW inverter and GEL batteries, then with your system, it should be quite simple. Just not sure how the Eastern Cape is in winter. Winter in JHB is actually pretty good in my opinion, as no rain and clear skies. I had no struggles in winter.

My system will be paid back in 2.5 years. I am almost halfway through now. It is getting sped up considerably as there are no more fixed charges (1.4k is not on my bill anymore). The GELs should last about 5 years, as they always have about 80% capacity left in the morning. Not a bad ROI, I must say. I sized my bank according to the DOD vs Cycle charts online and according to the spec sheet. That is where my 5 years come from. But It theoretically will be around 6/7. But I will be happy with anything over 3. I have balancers on all the batteries and have a fan running 24/7, keeping heat away in an outdoor enclosure that is in the shade.

My wife appreciates the work I did (self-installed). We had a few fights over my obsession with going off-grid, as she was just seeing the money being spent but not the vision I had. No surprise estimates and are insulated from the yearly price increases. I used to spend 3 to 4k a month on electricity and still got a 16k surprise bill from CP. That is what got me obsessed with going off-grid, and I developed a certain hatred of Citypower and Eskom🤣.

Edited March 24Mar 24 by Denns

1 hour ago, Denns said:

We had a few fights over my obsession with going off-grid

I think @Denns has more willpower than the average person if he manages to go off grid with a 3.6kW inverter and lead-acid batteries. Also a solar geyser?

A petrol generator is cheap but may not sync with the inverter, diesel is better but a bit more expensive. LPG generators seems even more expensive but should have long service intervals... buy a BYD Shark and use that as own generation when needed.

My intention is too see how well I can cope over the next 12 months with my current setup. If need be I can always have more batteries installed to offset for those days where the battery banks are not getting a full charge.

It is a great feeling knowing that when the power goes out again you don't have the stress and inconvenience of not having power. We are also water secure which was the first part of my long term vision being to being self-sufficient. With solar I don't have to worry any further about drawing buckets of water from the preverbial JoJo well.

2 hours ago, frivan said:

I think @Denns has more willpower than the average person if he manages to go off grid with a 3.6kW inverter and lead-acid batteries. Also a solar geyser?

A petrol generator is cheap but may not sync with the inverter, diesel is better but a bit more expensive. LPG generators seems even more expensive but should have long service intervals... buy a BYD Shark and use that as own generation when needed.

You could say that but it kind of becomes a lifestyle. You don’t notice after a while.

Yes I have a sole converted geyser. It’s geyser controller with 4 panels.

EVs sure are nice. Once the batteries are dead I will be getting an EV. And a 48V system with a 12kW inverter to handle the charging of the car.

1 hour ago, KAPLF said:

My intention is too see how well I can cope over the next 12 months with my current setup. If need be I can always have more batteries installed to offset for those days where the battery banks are not getting a full charge.

It is a great feeling knowing that when the power goes out again you don't have the stress and inconvenience of not having power. We are also water secure which was the first part of my long term vision being to being self-sufficient. With solar I don't have to worry any further about drawing buckets of water from the preverbial JoJo well.

Water is more important than electricity in my opinion. It was the first thing I ever did also. I supply the whole house with a JOJO tank. Pump only runs when a tap or shower opens.

16 hours ago, frivan said:

A petrol generator is cheap but may not sync with the inverter, diesel is better but a bit more expensive.

Why would a diesel generator do better than petrol? More torque, so runs at a more nearly constant speed?

14 hours ago, Denns said:

Water is more important than electricity in my opinion. It was the first thing I ever did also. I supply the whole house with a JOJO tank. Pump only runs when a tap or shower opens.

And the PV system powers the pump, so you have a constant supply.

I have a 2.5Kl tank. I calculate that will get us through a 10 day outage if we're careful. The longest we have had so far is 4 days.

We started with 7000l capacity and now have increased to 16000l. I run a 0.75kw pump. So far so good. Our scarcest resources going forward will be water and a reliable power supply.

2 hours ago, Bobster. said:

And the PV system powers the pump, so you have a constant supply.

I have a 2.5Kl tank. I calculate that will get us through a 10 day outage if we're careful. The longest we have had so far is 4 days.

Yeah, I did mine when the LS had stopped, so the chances of a power outage and a water outage were extremely low. My tank is 2050 litres. Also can push it to 10 days, as we have a pool also. But without worrying about consumption, we still had about half left after a 4-day outage, and the water came back. Pump is a 0.37kW. Single-story house, so we never have issues with pressure.

6 hours ago, Bobster. said:

Why would a diesel generator do better than petrol? More torque, so runs at a more nearly constant speed?

Something along those lines. I just know diesel generators have better load acceptance (handles bigger steps) than petrol and gas.

On 2026/03/23 at 7:28 PM, KAPLF said:

A new user here

I have just had my system switched on for a few days. The only power we have drawn from the grid is the small amount that trickles to the inverter

8kw Solis inverter

3 x solis 5kw batteries

12 x 550w panels.

I have a solar geyser and gas hob which helps a lot with limiting our usage

The installer set of DOD @50%. So far the lowest we have dropped battery backup at night was around 67%. The average has been in the 70s

My question is what will our solar generation output drop dramatically in the winter months in the eastern cape. Based on current output would we still make it on battery backup

I am also on the fence regarding registration with the council. My ideal scenario would be to have the system disconnected and only run our own power produced. I don't want to end up paying a massive fee monthly just to tied to the grid when I am not using the grid. The plan was to run for 12 months and see if we could survive on the current setup without being grid tied before having our supply disconnected. but with Eskom and municipalities threatening fines there is a lot of confusion as a new solar user as what is the best course of action.

Register with the council before end of March and take the plunge and disconnect from the grid or stay on the grid and pay the grid connection fee.

Advice would be appreciated in this matter

Before you pull the trigger on Eskom disconnection you need to evaluate scientifically. Most important factor consumption tied to discipline. "The cheapest kWh is the one you never have to generate"

There are important factors to take into account with your current system installed eg Solis 8kw Hybrid inverter that becomes less efficient when you remove 1 of the Hybrid blending sources. Your Solis 8kw inverter without AC input becomes strictly 8kw consumption no more surge capacity no more pass through rating strictly 8000w inverting capacity.

These are the metrics that needs to be calculated for off grid( Eskom discconect ion)

● L = Daily load (kWh/day)

● D = Autonomy days (use 3 days realistic)

● n_batt = Battery usable fraction (0.8 typical)

● n_sys = System efficiency (0.75 realistic off-grid)

● PSH = Peak Sun Hours (winter worst case ~4.0 Gauteng)

● F_overbuild = Oversize factor (2.5–3.0 off-grid reality)

Battery formula:

Kwh = L x D/ n_batt =3.75L

PV formula:

Kwp = L/PSH x n_sys x F_overbuild = L x 0.93 ( PV kWp ≈ Daily kWh (almost 1:1 for off-grid reliability)

If you allow generator support it reduces autonomy to 2 days, Reduce PV oversize to ~2.2 This massively drops system cost.

Example: 12kwh/day:

●Battery: 12 x 3.75 = 45 kWh

●PV: 12 x 0.93 = 11.2 kWp

1 hour ago, TaliaB said:

"The cheapest kWh is the one you never have to generate"

This is so true... and the most expensive kWh is the one you don't have when you need it...

To clarify

I would then need to increase my battery capacity. So currently 15 kw/h adding an extra 10 kw/h. As stated SOD is set to 50%. So we would have to increase to 80% to maximise the available battery backup for extended days outage. We cannot add more panels are there is no more available roof space.

Can another brand of battery be used in conjunction with the Solis batteries or is it best practice to stay with one brand.

It will be interesting to see how my current system performs as we go into winter.

2 hours ago, TaliaB said:

Before you pull the trigger on Eskom disconnection you need to evaluate scientifically. Most important factor consumption tied to discipline. "The cheapest kWh is the one you never have to generate"

There are important factors to take into account with your current system installed eg Solis 8kw Hybrid inverter that becomes less efficient when you remove 1 of the Hybrid blending sources. Your Solis 8kw inverter without AC input becomes strictly 8kw consumption no more surge capacity no more pass through rating strictly 8000w inverting capacity.

These are the metrics that needs to be calculated for off grid( Eskom discconect ion)

● L = Daily load (kWh/day)

● D = Autonomy days (use 3 days realistic)

● n_batt = Battery usable fraction (0.8 typical)

● n_sys = System efficiency (0.75 realistic off-grid)

● PSH = Peak Sun Hours (winter worst case ~4.0 Gauteng)

● F_overbuild = Oversize factor (2.5–3.0 off-grid reality)

Battery formula:

Kwh = L x D/ n_batt =3.75L

PV formula:

Kwp = L/PSH x n_sys x F_overbuild = L x 0.93 ( PV kWp ≈ Daily kWh (almost 1:1 for off-grid reliability)

If you allow generator support it reduces autonomy to 2 days, Reduce PV oversize to ~2.2 This massively drops system cost.

Example: 12kwh/day:

●Battery: 12 x 3.75 = 45 kWh

●PV: 12 x 0.93 = 11.2 kWp

While I somewhat agree with this. I do think some of the factors are a bit overdone. For other references I used, they mostly sized their battery for 1 day's consumption. Past a certain point it just becomes very un-economical. I for example only have 12kWh but the lowest it has ever hit is 7.2kWh having used about 40% of the capacity.

Where I oversized was the PV side of things. My typical load on the house is around 10kWh a day (Geyser is on the controller and have no way of measuring that due to the output of the controller not being a typical wave). My PV (for supplying the house), is only 5.17kW. But that translates to an average generation of 21kWh. That is 4 times what I need so if the sun remotely comes out for an hour or so I am fine.

The bulk of my consumption is the pool and fish pond pumps. Shedding those 2 during cloudy conditions, my consumption drops to around 4 to 5kWh. This goes in line with the 1 day rule (LA batteries for 50% is 6kWh).

I have survived just fine with little to no issues. I would focus on killing unnecessary loads as you say when the need arises, maximising the panels but would leave the batteries enough for 1 day. Just get a small inverter generator that only charges batteries and that's it.

Edited March 26Mar 26 by Denns

On 2026/03/23 at 7:28 PM, KAPLF said:

A new user here

I have just had my system switched on for a few days. The only power we have drawn from the grid is the small amount that trickles to the inverter

8kw Solis inverter

3 x solis 5kw batteries

12 x 550w panels.

I have a solar geyser and gas hob which helps a lot with limiting our usage

The installer set of DOD @50%. So far the lowest we have dropped battery backup at night was around 67%. The average has been in the 70s

My question is what will our solar generation output drop dramatically in the winter months in the eastern cape. Based on current output would we still make it on battery backup

I am also on the fence regarding registration with the council. My ideal scenario would be to have the system disconnected and only run our own power produced. I don't want to end up paying a massive fee monthly just to tied to the grid when I am not using the grid. The plan was to run for 12 months and see if we could survive on the current setup without being grid tied before having our supply disconnected. but with Eskom and municipalities threatening fines there is a lot of confusion as a new solar user as what is the best course of action.

Register with the council before end of March and take the plunge and disconnect from the grid or stay on the grid and pay the grid connection fee.

Advice would be appreciated in this matter

On an average day for an average user even in Winter you'll be fine, or you could make do. This is considering the 6.6kW of panels would generate around 20kWh, and you've got solar water heating and gas cooking to go with it, and you've got reasonable battery storage. On a clear Winter's day you could still get close to 30kWh if you had enough storage, but on heavy overcast days you might get just 5kWh. All thumbsucks based on personal usage along the Sunshine Coast.

So of course there will be days (sometimes several in a row) where cloud cover prevents meaningful power generation. Question is how you want to handle that, and the question then is what municipality you're in and what do they actually charge for grid fees? If it's Nelson Mandela Bay, for a grid-tied user on TOU it's around R117pm excl VAT. I don't think it's worth it to go off-grid in this case, if it means running a generator, but that's just me.

The easiest way to test if you can cope without Eksdom is to turn off the main feed to your house, either at the kiosk outside or on your main DB. If you don’t have to turn it on again for a year, you know you are fine.