Nickvdv

Hi all,
thank you for all the feedback, I really appreciate the time you've taken to respond.
My takeaway is that the R 22k/R 30k might be better spent on additional panels + a lower wattage heating element, and rely on batteries or grid power (if batteries are low) to prepare hot water early mornings.
The requirement would be to get an inverter which would allow to make the decision to use grid power for the geyser if batteries are below x percent. Optional additional battery if we still rely too much on grid power, but ROI calculation for that can be done afterwards depending on what the remaining grid power draw would be.
I'll try to leave space above the current geyser in case we'd ever reconsider the EV solar geyser, but we'll leave that cost out for now.
 
Thank you @mzezman, @Chris_S, @iiznh, @BritishRacingGreen, @TimCam and @cbrunsdon for your valuable inputs - much appreciated.
 

https://www.voltex.co.za, but different prices for different "customers".
 

Just a gut feeling, but I'm not convinced that solar water heating - any type - is right for your needs or your usage pattern. Just too much hot water demand at the wrong time for a solar water heater to make the impact you think it will. It follows, I think your estimates of cost savings are optimistic, and you may end up being disappointed. I really think you should consider a heat pump instead, and couple it with solar PV, but a reduced number of panels.
Why do I say this? Firstly, you can discount the solar contributing anything meaningful towards the morning hot water. The 150l geyser will be cold from the night before, and you will need to power it up using electricity, because the solar water heater won't give any useful contribution before 9-10am. It doesn't make sense using a solar PV system with storage for this either, because the cost of 7kWh of batteries should set you back around R45K-plus, and you'll need it all every morning if you keep a conventional element, leaving no room to use those batteries for anything else during the night.
In the afternoon you could heat the water from solar, and say by around 4pm you could have 150l of hot water as long as it's a sunny day, but the sun won't help you much after 4pm regardless. You'll have to keep re-heating water to 8pm as  you are doing now to ensure that everyone gets a decent shower, and a lower-wattage 1.5kW or 2kW element will just take longer to re-heat the geyser and probably frustrate everyone. Not to mention, running the geyser during peak hours is just... not nice to Eskom. But bottom line, I think you would be lucky to save 6-8kWh per day with a solar solution. Always open to debate, I stand to be corrected (best with actual measurement of power used over time), but here I stand nonetheless.

Hi all,
thank you for all the feedback, I really appreciate the time you've taken to respond.
My takeaway is that the R 22k/R 30k might be better spent on additional panels + a lower wattage heating element, and rely on batteries or grid power (if batteries are low) to prepare hot water early mornings.
The requirement would be to get an inverter which would allow to make the decision to use grid power for the geyser if batteries are below x percent. Optional additional battery if we still rely too much on grid power, but ROI calculation for that can be done afterwards depending on what the remaining grid power draw would be.
I'll try to leave space above the current geyser in case we'd ever reconsider the EV solar geyser, but we'll leave that cost out for now.
 
Thank you @mzezman, @Chris_S, @iiznh, @BritishRacingGreen, @TimCam and @cbrunsdon for your valuable inputs - much appreciated.
 

Hi all,
thank you for all the feedback, I really appreciate the time you've taken to respond.
My takeaway is that the R 22k/R 30k might be better spent on additional panels + a lower wattage heating element, and rely on batteries or grid power (if batteries are low) to prepare hot water early mornings.
The requirement would be to get an inverter which would allow to make the decision to use grid power for the geyser if batteries are below x percent. Optional additional battery if we still rely too much on grid power, but ROI calculation for that can be done afterwards depending on what the remaining grid power draw would be.
I'll try to leave space above the current geyser in case we'd ever reconsider the EV solar geyser, but we'll leave that cost out for now.
 
Thank you @mzezman, @Chris_S, @iiznh, @BritishRacingGreen, @TimCam and @cbrunsdon for your valuable inputs - much appreciated.
 

Hi all,
thank you for all the feedback, I really appreciate the time you've taken to respond.
My takeaway is that the R 22k/R 30k might be better spent on additional panels + a lower wattage heating element, and rely on batteries or grid power (if batteries are low) to prepare hot water early mornings.
The requirement would be to get an inverter which would allow to make the decision to use grid power for the geyser if batteries are below x percent. Optional additional battery if we still rely too much on grid power, but ROI calculation for that can be done afterwards depending on what the remaining grid power draw would be.
I'll try to leave space above the current geyser in case we'd ever reconsider the EV solar geyser, but we'll leave that cost out for now.
 
Thank you @mzezman, @Chris_S, @iiznh, @BritishRacingGreen, @TimCam and @cbrunsdon for your valuable inputs - much appreciated.