Hi guys, I need some guidance on how to maintain peace with the Minister of Hot Water in the household in winter.

Current Setup;

• 200l above roof solar geyser with tubes and 4kw element controlled via geyserwise

• Basic Go-Solr system with 5kw inverter, 10kwh battery and 3.6kw solar plant

In Summer, Battery bank is usually full by around 11am and geyserwise kicks in and takes water to max of 75 degrees. Enough for 2 evening showers. Geyser runs for about 30mins At around 4am to take water to about 55c but then it’s eating to batteries but it’s minimal. All in all, I’m able to run household with very little to no need for Eskom on most days.

in Winter, the system struggles and realises heavily on Eskom and sometimes the water just isn’t hot enough, leading to much gnashing of teeth from you know who.

What’s the best bang for buck way to lower dependence on Eskom and have reliable supply of hot water in winter ?

• Adding a heat pump ? How should that be integrated into the existing system for it to be optimal ? And what size heat pump?

• Adding a second geyser ? How should that be connected ?

• Doing both ?

• Other creative methods ?

1 hour ago, King_M said:

Hi guys, I need some guidance on how to maintain peace with the Minister of Hot Water in the household in winter.

Current Setup;

• 200l above roof solar geyser with tubes and 4kw element controlled via geyserwise

• Basic Go-Solr system with 5kw inverter, 10kwh battery and 3.6kw solar plant

In Summer, Battery bank is usually full by around 11am and geyserwise kicks in and takes water to max of 75 degrees. Enough for 2 evening showers. Geyser runs for about 30mins At around 4am to take water to about 55c but then it’s eating to batteries but it’s minimal. All in all, I’m able to run household with very little to no need for Eskom on most days.

in Winter, the system struggles and realises heavily on Eskom and sometimes the water just isn’t hot enough, leading to much gnashing of teeth from you know who.

What’s the best bang for buck way to lower dependence on Eskom and have reliable supply of hot water in winter ?

• Adding a heat pump ? How should that be integrated into the existing system for it to be optimal ? And what size heat pump?

• Adding a second geyser ? How should that be connected ?

• Doing both ?

• Other creative methods ?

Just a warning. A heat pump is great and I have mine now for 14yrs. In winter with temps at close to zero the COP can be as low as 1 and in summer 3-4 times or more for a modern unit. Thus the heat pump does not help for winter.

1 hour ago, King_M said:

Hi guys, I need some guidance on how to maintain peace with the Minister of Hot Water in the household in winter.

Current Setup;

• 200l above roof solar geyser with tubes and 4kw element controlled via geyserwise

• Basic Go-Solr system with 5kw inverter, 10kwh battery and 3.6kw solar plant

In Summer, Battery bank is usually full by around 11am and geyserwise kicks in and takes water to max of 75 degrees. Enough for 2 evening showers. Geyser runs for about 30mins At around 4am to take water to about 55c but then it’s eating to batteries but it’s minimal. All in all, I’m able to run household with very little to no need for Eskom on most days.

in Winter, the system struggles and realises heavily on Eskom and sometimes the water just isn’t hot enough, leading to much gnashing of teeth from you know who.

What’s the best bang for buck way to lower dependence on Eskom and have reliable supply of hot water in winter ?

• Adding a heat pump ? How should that be integrated into the existing system for it to be optimal ? And what size heat pump?

• Adding a second geyser ? How should that be connected ?

• Doing both ?

• Other creative methods ?

Gas geyser? From your description it will only get used in winter, so about 3 months which is how long a 48kg bottle lasts when gas heating is used alone. In your case you wont even hit half the bottle after winter is done.

That or just keep using Eskom. Any reason you dont want to use Eskom? I am completely off-grid with Citipower having removed their meter and cut the cable so for someone like me I can justify spending to cater for such situations, but in your case, unless you want to be off-grid, dont waste your money catering for 3 months of the year. Just spend the extra on eskom and call it a day. It will take you a decade to recover your money on any solution that will cover winter.

Heat pump is a no as Scorp has said for winter.

Adding a second geyser is a no also as it sounds like you cant even get the one geyser to full temp in winter, how will you do 2?

My recommendation is leave as is and spend the few hundred rand from eskom.

Edit: Does seem newer HPs still work fine in sub zero temps. Older models struggle.

Edited February 27Feb 27 by Denns

21 minutes ago, Denns said:

Gas geyser? From your description it will only get used in winter, so about 3 months which is how long a 48kg bottle lasts when gas heating is used alone. In your case you wont even hit half the bottle after winter is done.

That or just keep using Eskom. Any reason you dont want to use Eskom? I am completely off-grid with Citipower having removed their meter and cut the cable so for someone like me I can justify spending to cater for such situations, but in your case, unless you want to be off-grid, dont waste your money catering for 3 months of the year. Just spend the extra on eskom and call it a day. It will take you a decade to recover your money on any solution that will cover winter.

Heat pump is a no as Scorp has said for winter.

Adding a second geyser is a no also as it sounds like you cant even get the one geyser to full temp in winter, how will you do 2?

My recommendation is leave as is and spend the few hundred rand from eskom.

Great answer to this winter problem. In line with one of my minor problems. I want to move panels from car port to a massive N facing roof but the bit I have to use grid does not warrant the cost of rewiring and all the hardware. It could take 10yrs for a ROI. We have a stable grid and I could adapt and found out on the single days I forgot to switch my PV on after big electric storms.

@King_M ,

If your inverter can handle it, then I would add a few more panels to better cover the winter periods.

You can also just replace your 4kW element with a 3 or even 2kW one to better use your PV.

34 minutes ago, Sidewinder said:

@King_M ,

If your inverter can handle it, then I would add a few more panels to better cover the winter periods.

You can also just replace your 4kW element with a 3 or even 2kW one to better use your PV.

I read the problem as the capacity of the battery being low for the morning heating. Small value element would need longer run time but use the same energy. The gas geyser in series would solve this problem as mentioned earlier. It need not be a big unit.

55 minutes ago, Sidewinder said:

@King_M ,

If your inverter can handle it, then I would add a few more panels to better cover the winter periods.

You can also just replace your 4kW element with a 3 or even 2kW one to better use your PV.

Agree with both points.

Running a 4kW load in the early morning off a 10kWh battery would drop it's capacity/SOC by 20% in half an hour of use - with a 2kW element that would be only 10% - much easier on a battery that is already at a low SOC early in the morning in winter... This would also allow you to start the geyser's daytime heating cycle earlier in the mornings, and to run it later in the afternoons (when the PV panels might not produce sufficient power for the 4kW element).

You mention that your system has a 3.6kW "solar plant" - that's presumably the solar panels? If so, then heating a 4kW element will likely always need a push from the battery - even during peak daytime production. Can you please give us some specifics about your solar panels and inverter specs - adding a few more solar panels might just be the easiest solution if your system can accommodate them.

3 hours ago, Scorp007 said:

Thus the heat pump does not help for winter.

I'm another long time heat pump owner (so my pump is not as efficient as those you buy now) and I disagree with this. It is true that the pump is slower in the winter BUT I can run on it the backed-up side of my PV system. Because of that I think it's a good option. I am not using grid electricity to run my pump.

Also I checked the data from my PV system for July. In the morning the pump runs for an hour - that's what I allocated it on it's own timer. I don't check the temperature every time, but I don't recall getting into the shower and thinking that it's a bit cold. The second run starts at 12:00 and the timer will let it run until 15:00, but actually and in the winter, it runs for about 45 minutes

1 hour ago, HennieL said:

Agree with both points.

Running a 4kW load in the early morning off a 10kWh battery would drop it's capacity/SOC by 20% in half an hour of use - with a 2kW element that would be only 10% - much easier on a battery that is already at a low SOC early in the morning in winter... This would also allow you to start the geyser's daytime heating cycle earlier in the mornings, and to run it later in the afternoons (when the PV panels might not produce sufficient power for the 4kW element).

You mention that your system has a 3.6kW "solar plant" - that's presumably the solar panels? If so, then heating a 4kW element will likely always need a push from the battery - even during peak daytime production. Can you please give us some specifics about your solar panels and inverter specs - adding a few more solar panels might just be the easiest solution if your system can accommodate them.

That doesnt help him, element size is irrelevant. If he needs 8kWh to heat the geyser then it will take 2 hours vs 4 hours with a 2kW. The energy requirement is the same. More panels also wont help. The issue is not enough storage from the battery to heat.

People shower mostly before 7 in the mornng or 8. Depends on work hours, in winter, you generate next to nothing at those hours. generation is also poor after 4pm. His problem is storage. Both hot water storage and battery storage. Which will amount to the same as just installing a gas geyser which will guarantee all the hot water he needs in winter with minimal gas usage.

1 hour ago, Bobster. said:

I'm another long time heat pump owner (so my pump is not as efficient as those you buy now) and I disagree with this. It is true that the pump is slower in the winter BUT I can run on it the backed-up side of my PV system. Because of that I think it's a good option. I am not using grid electricity to run my pump.

Also I checked the data from my PV system for July. In the morning the pump runs for an hour - that's what I allocated it on it's own timer. I don't check the temperature every time, but I don't recall getting into the shower and thinking that it's a bit cold. The second run starts at 12:00 and the timer will let it run until 15:00, but actually and in the winter, it runs for about 45 minutes

For the OPs case even if a heatpump works or not it is technically still irrelevant as he will never get his money back on the investment. 25k for heat pump, 15k for gas geyser, 20k or so for solar upgrades. To save a few hundred rand a month in electric use for 3 months? It is not practical and he should just leave the system as is unless going offgrid which he isnt.

I think we mostly forget why we have solar. Its backup power and saving money. Worrying about using an extra 100 units over winter defeats the purpose of the later. Unless the grid is so bad that you wind up bathing with cold water. These days, load shedding isnt an issue anymore.

Edited February 27Feb 27 by Denns

1 hour ago, Denns said:

These days, load shedding isnt an issue anymore.

"Shapes of things to come". I agree on the ROI but it isn't always about the money especially if the misses needs hot water no matter the time of day, let's be honest guys they rule the roost.

That said I agree with @Bobster. in the sense of heatpump effiency. During summer times obviously the heat pump is more effiecient but not to say it becomes useless during winter. The COP in summer around 3.5 COP winter depending on outside tempreture and heatpump quality around 2~2.5 COP. Heatpump becomes less efficient in sub zero tempratures as it extract heat from the outside environment.

Between installing solar panels vs heatpump the latter will always be more effiecient. The way to go is running heatpump from inverter( solar) with controll to protect the battery Soc.

Heat pumps are significantly cheaper to run for water heating compared to gas heaters.

2 hours ago, Denns said:

For the OPs case even if a heatpump works or not it is technically still irrelevant as he will never get his money back on the investment. 25k for heat pump, 15k for gas geyser, 20k or so for solar upgrades. To save a few hundred rand a month in electric use for 3 months? It is not practical and he should just leave the system as is unless going offgrid which he isnt.

Agreed. I had a heat pump before I had solar, so my strategy was different. I figured out that I could have hot water despite load shedding. But load shedding isn't with us any more, and so that's no longer a strong card to play.

If your love does not have limits, you don't have love. Same applies to hot water.

1 hour ago, frivan said:

If your love does not have limits, you don't have love. Same applies to hot water.

Hot water isn’t about limits it’s about system design. If your system can’t handle normal domestic expectations, that’s not philosophy that’s undersizing. Love may have limits. Good engineering shouldn’t.

2 hours ago, TaliaB said:

Hot water isn’t about limits it’s about system design. If your system can’t handle normal domestic expectations, that’s not philosophy that’s undersizing. Love may have limits. Good engineering shouldn’t.

You are contradicting yourself. System design has an upper limit. Domestic expectation implies a limit.

If anyone wants to open a tap and expect warm water forever, I suggest a fire tube boiler.

@King_M I suggest having the Minister of Hot Water describing her expectation and then deciding on the most efficient solution.

14 hours ago, TaliaB said:

"Shapes of things to come". I agree on the ROI but it isn't always about the money especially if the misses needs hot water no matter the time of day, let's be honest guys they rule the roost.

That said I agree with @Bobster. in the sense of heatpump effiency. During summer times obviously the heat pump is more effiecient but not to say it becomes useless during winter. The COP in summer around 3.5 COP winter depending on outside tempreture and heatpump quality around 2~2.5 COP. Heatpump becomes less efficient in sub zero tempratures as it extract heat from the outside environment.

Between installing solar panels vs heatpump the latter will always be more effiecient. The way to go is running heatpump from inverter( solar) with controll to protect the battery Soc.

Heat pumps are significantly cheaper to run for water heating compared to gas heaters.

I somewhat agree but I still don’t see why he can’t spend 300 rand a month from the grid for the extra 100kwh for extra heating during winter since he is basically completely running the geyser off solar the other months.

it would theoretically take him 25 years to get his money back on a HP, maybe under 20 years factoring the increases.

I only recommended the gas heater as he may use less than half a 48kg bottle in a year. Could even be less if used with a Dewhot valve set at 41 degrees. So about 1000 rand a year tops which does come to the cost of running off the grid during those 3 months.

11 hours ago, TaliaB said:

Hot water isn’t about limits it’s about system design. If your system can’t handle normal domestic expectations, that’s not philosophy that’s undersizing. Love may have limits. Good engineering shouldn’t.

I had the OPs problem also. Tried imposing limits on showering or baths (they love baths) and hot water was always an issue. So just had the geyser converted to solar using a controller connected to 4 panels with my inverter connected via a timer to the controller to assist heating if need be.

No limits on her anymore and she fills the tub as much as she wants in the evening and showers every morning. I am yet to use the inverter to assist and have a 150 litre geyser.

But on that note, if they are only 2 people. I wonder how a 200 litre geyser isn’t enough. My 150 litre has been plenty for my wife and I. And had 5 people sleep over for a month and didn’t have any issues.

Maybe the wife is going overboard with the geyser excessively.

Some people have a habit of using hot water for rinsing dishes and washing their hands... Connect the hot water tap to the cold water supply, that solves it.

18 hours ago, Denns said:

That doesnt help him, element size is irrelevant. If he needs 8kWh to heat the geyser then it will take 2 hours vs 4 hours with a 2kW. The energy requirement is the same. More panels also wont help. The issue is not enough storage from the battery to heat.

I respectfully beg to differ... I don't dispute that (say) a 200 liter geyser would require about 4.65kWh to heat the water from 40C to 60C, regardless of the element rating, and that the 4kWh element would do this in half the time that a 2kW element would...

My point is that the 2kW element will be able to start heating earlier, and stop later, than the 4kW unit if it only uses solar - and that would make a difference. In my experience, a geyser element (or a stove) wants to be fed it's full "load requirement", thus a 4kW element will pull 4 kW if that is available, regardless if this comes from solar panels, the grid, or a battery (unlike when an inverter charges a battery, that might only push 200W into a 10kWh battery if that is all that is available). So, a 2kW element will be able to start up much earlier in the day than a 4kW element, as the panels will be able to produce the 2kW much earlier than 4 kW, and the same goes for the afternoons.

Another advantage would be that the 2kW element would not likely "overload" the 5kW inverter when used during the day, whilst the 4kW element would only leave 1kW "spare" for the rest of the house loads when it is heating the water.

Regarding the "upgrading cost comparison"... Not knowing the OP's system (how many panels of what Wattage, etc.) we will have to make some assumptions (and I hate doing that... but lets bite the bullet...). @King_M stated in his first post that he has 3600Wp panel output and a 5kW inverter - Adding (say) 4 x Canadian Solar 108 cell 405W panels at R1 221.3 (current price VAT Inclusive from a reputable dealer in Bloemfontein) would only cost R4 885.20 (plus installation cost...) to increase his maximum yield from 3.6kWp to 5.2kWp. Obviously this is only an example, and if the panels mentioned are not compatible with the existing panels, or if the inverter/MPPT can not safely handle the Isc and Voc, then one would have to look at using different panels...

Obviously, your "do nothing and pay for grid power" is also a valid argument, and if the addition of a few extra solar panels is not an option, then your argument does make financial sense.

8 hours ago, HennieL said:

I respectfully beg to differ... I don't dispute that (say) a 200 liter geyser would require about 4.65kWh to heat the water from 40C to 60C, regardless of the element rating, and that the 4kWh element would do this in half the time that a 2kW element would...

My point is that the 2kW element will be able to start heating earlier, and stop later, than the 4kW unit if it only uses solar - and that would make a difference. In my experience, a geyser element (or a stove) wants to be fed it's full "load requirement", thus a 4kW element will pull 4 kW if that is available, regardless if this comes from solar panels, the grid, or a battery (unlike when an inverter charges a battery, that might only push 200W into a 10kWh battery if that is all that is available). So, a 2kW element will be able to start up much earlier in the day than a 4kW element, as the panels will be able to produce the 2kW much earlier than 4 kW, and the same goes for the afternoons.

Another advantage would be that the 2kW element would not likely "overload" the 5kW inverter when used during the day, whilst the 4kW element would only leave 1kW "spare" for the rest of the house loads when it is heating the water.

Regarding the "upgrading cost comparison"... Not knowing the OP's system (how many panels of what Wattage, etc.) we will have to make some assumptions (and I hate doing that... but lets bite the bullet...). @King_M stated in his first post that he has 3600Wp panel output and a 5kW inverter - Adding (say) 4 x Canadian Solar 108 cell 405W panels at R1 221.3 (current price VAT Inclusive from a reputable dealer in Bloemfontein) would only cost R4 885.20 (plus installation cost...) to increase his maximum yield from 3.6kWp to 5.2kWp. Obviously this is only an example, and if the panels mentioned are not compatible with the existing panels, or if the inverter/MPPT can not safely handle the Isc and Voc, then one would have to look at using different panels...

Obviously, your "do nothing and pay for grid power" is also a valid argument, and if the addition of a few extra solar panels is not an option, then your argument does make financial sense.

Well articulated but we need more data. Are the 10kWh batteries fully charged in winter? I guess not.

If not then PV is the cheaper option. If they there will not be enough PV in order to add another battery.

As requested much earlier one needs more data to give good guidance.

11 hours ago, frivan said:

Some people have a habit of using hot water for rinsing dishes and washing their hands... Connect the hot water tap to the cold water supply, that solves it.

I don't know why this never occurred to me.

On 2026/02/28 at 5:08 PM, Scorp007 said:

Well articulated but we need more data. Are the 10kWh batteries fully charged in winter? I guess not.

If not then PV is the cheaper option. If they there will not be enough PV in order to add another battery.

As requested much earlier one needs more data to give good guidance.

I suspect they are fully charged. He says his batteries are charged by 11am in summer. So winter I would guess around 1/2 they are charged.

Thank you very much for sharing your wealth of knowledge here folks. Highly, highly appreciate this. Definitely saved me some money that I was ready to spend on an ITS unit.

I guess I'm dealing with a similar problem that most of you encounter - Striking the balance between trying to save money, have reliable supply of electricity and maintain peace in the household.

Seeing that I've been running on a rental system (GoSolr) who's contract comes to an end in a few months time and with prices certainly being a lot more friendlier than they were when I rented the GoSolr system 3 years back, I will hold out for now and rather focus on Investing on my own system that will give me enough headroom to run through Winter with enough power to spare.

On 2026/02/27 at 12:48 PM, HennieL said:

Agree with both points.

Running a 4kW load in the early morning off a 10kWh battery would drop it's capacity/SOC by 20% in half an hour of use - with a 2kW element that would be only 10% - much easier on a battery that is already at a low SOC early in the morning in winter... This would also allow you to start the geyser's daytime heating cycle earlier in the mornings, and to run it later in the afternoons (when the PV panels might not produce sufficient power for the 4kW element).

You mention that your system has a 3.6kW "solar plant" - that's presumably the solar panels? If so, then heating a 4kW element will likely always need a push from the battery - even during peak daytime production. Can you please give us some specifics about your solar panels and inverter specs - adding a few more solar panels might just be the easiest solution if your system can accommodate them.

Yes, I almost always dip into my fully charged batteries with the midday geyser run and the morning geyser run completely obliterates the batteries down to about 25% or so

2 hours ago, King_M said:

Yes, I almost always dip into my fully charged batteries with the midday geyser run and the morning geyser run completely obliterates the batteries down to about 25% or so

From the value of 2330Wh per 10 degrees you can calculate the power needed once you have data of what temp the geyser is during to early mornings in order to get to your desired temp for the morning showers.

Also based on the replies the battery SOC in the winter is important as you did indicate the summer time the battery is full. Winter can be the killer as well as the area you reside.

The after the midday run in winter would be the stat to use or the 00h00 SOC to have some idea of power used from battery during the cooking run at night as the value used by the kitchen can vary like a piece of string. Cooking chicken in the oven can be 60min yet doing prego roll fillets might need only 15min for 4-6 pieces. Add rice and potatoes can add another 15min each on a stove plate. Not much power but all adds up.