https://www.4x4community.co.za/forum/showthread.php/372332-Heating-water-directly-from-solar-panels
See this discussion on a friendly forum by Willem Wikkel Spies.
He is from Heidelberg (a boer stronghold during the Boer war). I trust that the indomitable spirit of that town lives on and that we can simplify all this complexity wrt water heating.
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Saw this quote:
Inverters are inefficient and are unreliable since they are high power electronic devices.
Yeah, that is not true.
Either get evacuated tubes, grid tied or upsize your hybrid. The direct PV geyser controllers on the market range from questionable to certified firestarters.
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Of course that’s a pun on “William Shakespeare”, translitterated “shake spear”, which would properly translate to Wikkelspies (one word). Also an euphemism for some solitary… uuuhm… entertainment.
Unless of course his last name actually is Spies.
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Just on the inverter question how long do they last?
If you buy something reputable that quotes EU-efficiency, probably long enough. If you buy an Axpert-type; start saving for a new one.
Long enough for what?
To be a piece of string?
How long do you want it to last. On average it would outlast a direct PV controller, as well as the pump in pumped evacuated tube systems, nevermind the one-way valve. In fact it’s very likely going to outlast the geyser in an evacuated tube system.
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Yeah, I can attest to that. The entire EV system had to be replaced after 9.5 years, that is the tubes, the Geyserwise Controller box, the pump and the “10-year” “no warranty joke” geyser too.
Whilst it worked nirvana!
After lots of research, all the new ideas out there, heat pumps, just get a blerrie Solis Grid-tied inverter and be done with it.
What is being missed by “some”, WHEN the geyser/s is/are heated, what to do with the panels sitting in the sun? Solis can feed that spare power into the rest of the house when there is no LS.
Dang, IF it is your “thing”, sell the spare power from the Solis back to CoCT.
KISS.
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And his parents gave him the middle name “Wikkel”. Well, maybe it’s a tradition in their family.
It’s not the cheapest solution, but it works for me. Heatpump to heat the geyser, and heatpump is powered by my hybrid system.
I had the heatpump before I had solar.
It’s more efficient than a traditional element, with or without all those thermostat control goodies.
I never don’t have hot water.
Titbit on Heidelberg:
If memory serves, there was this guy in Heidelberg, he had one ma-moerse DIY solar tracker he erected, to point the panels optimally to the sun.
He ran his lead acid batteries and Axpert inverter flatout, house, cooking, welding, you name it.
He got very chaffed and excited about how cool his system worked. That the tracker is the “solution”.
Some of us pointed out, running lead acids that hard and that low, with the Axpert charging bug, yeah, not a long-term solution, panels being optimal or “te not”.
Then one day he went deadly quiet. Not a peep out of him suddenly. I never knew what happened.
He reminded me of this “in the paper” Melkbos guy who makes so much money off his DIY feeding back.
Heating water is no rocket science, no new “wow, I have the best ever new solution”. 
Hot water is going to cost … finish en klaar.
Do it optimally. Wisely. Try doing it for ±20 years if you can, using quality products with a 20 year warranty INVERTER.
Victron units typically last at least a decade and there are many examples of units that lasted even longer than that. It is somewhat hard to say, because once a unit is out of warranty, the company generally won’t know if/when it fails.
What you need to do is draw a histogram of the entire “population” of units, by age, and how many remains by year x, and most companies are simply not going to have that data.
We do know however, as @_a_a_a said, that the tank alone (in a retrofit pumped solution with an evac tube collector) probably has a life of about 5 years. From experience I know that the high end thermosyphon solar water heaters (my parents have a Siemens indirect one for example) can last 30 years. Anything outside of the highest of high end… will not outlast a good inverter.
Mr Shakespeare’s primary motivation appears to be that he wants to sell you a product, and hence a stick is needed to beat the opposition.
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I’d like to see what he came up with in the end, but I can’t see how it’s different to what is already available and safe to use.
But hey, we might be wrong and there might come some perfect solution out of it, but I think it will be a fit for a small group of people.
Well, doesn’t have to be Solis, but yes! Why not have your panels for your geyser go one step further and feed the house?!
I’m assuming price is a part of the equation here. A proper grid-tied inverter is not all that cheap.
In my case I did it similar to @Bobster by going with a heat pump. As I knew I was getting a Victron system (but still saving up for it) I did it in stages like this:
- Heat pump for geyser
- Inverter & batteries for loadshedding (replacing the trolley)
- Panels & MPPTs
To be honest I just recommend everyone to get a heat pump. But I’m not against a smaller element or extra panels to do it.
How I looked at it:
- Cost of heatpump (and Geyserwise with panels) ±R25k-R30k?
1.1) How long will it last? How long is a piece of string? - Cost of a 3kw (?) Solis as we have solar already so what (?) ±R10k
2.1) PLUS an additional >10 year warranty bought if you want.
2.2) How long will it last? You are covered by the warranty and/or the extension you bought.
The panels, ±R15k installed for 3kw + Solis (±R10K) vs ±R25k-R30k for heat pump/Geyserwise solution?
BUT!!! the cost of the panels are offset towards heating the geyser/s AND overall towards the house in total. Maybe even selling back one day.
I THINK I got it all covered.
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I read so much here about all the options available and what will be the best in the long and short term solution wise for water heating, dc element, evacuated tubes, grid tie AC inverters, heat pumps etc.
And then I think, my setup, as conventional as it is serves my so well, ROI not factored in here.
Standard geyser, 2Kw element, large enough battery bank (is there such a thing?), sufficient panels, and “some” management here and there in terms of household usage and weather patterns - and everything just works.
If you manage a little, it is no problem to heat your water from batteries and have sufficient battery capacity. Must add that we are only 3 in the house, mostly one daily shower each (but not because you can’t have more) and only one 150L geyser.
So for me it would make no sense to explore other solutions which will not pay for itself. The system works so well, I couldn’t be happier.
For the past 4 months our electricity bill averages around R10 - R18.00
And this is only because of the inevitable delay when the grid comes back and for a couple of minutes the lion’s share is taken from the grid. Hardwired into the inverter I suppose. If this didn’t happen, my consumption would be zero.
I know people have installed big cool systems, catering for their WANTS … systems that work beautifully, saving a ton of cash towards Eskom BUT …
Point 1: My first and foremost consideration was ROI with LS an accidental side benefit.
Point 2: Starting in 2008, doing the upgrades and making mistakes, eventually getting the “right stuff” it dawned upon me to factor in the inevitable replacement costs down the line, the timing of that cost is also VERY important.
Nothing lasts forever. Nothing.
So when Point 2 has to happen, Point 1 becomes a very big point of consideration, making one ponder the seriousness of considering “Does it still make financial sense?”
And IF the batts we paid for with kidneys don’t last as “advertised”, o donner.
Another titbit:
Like people install gas, saving TONS on Eskom!!! We went gas and are saving sooooo much …
Yeah, does not work like that.
The budget spreadsheet just got a new column called: Gas Purchases.
Going gas because of LS woes, understanding the above, is a whole different matter altogether.
Just some context I see happening all over forums.
Seldom it does. But to keep our sanity is priceless. Only very carefully though out systems. But I learned so much here I think I’m good. Luckily did not have to get rid of kidneys and in 10 years who knows what excellent type of batteries will be available at a fraction of today’s cost.
And Victron being modular, makes this even better in terms of replacement down the line.
But agree with everything you said.
My Kwikhot Kwikpump was installed in September 2011. Still going strong.
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This!!!
Our gas (and I always keep two full 19kg cylinders handy) is actually a backup. Use the blerrie stove I tell the wife, gas is expensive!
But I don’t mind, one cylinder lasts us 6-8 months and most of the heating is done with air fryer or microwave. The inverter and batteries laughs at these two items. But one at a time, I insist on this.
That is really nice!!!
… BUT …
Nothing lasts forever. Nothing.
WHEN it needs replacement, and it always happens at the most inconvenient financial time, that is when we do “the sums” in a whole new manner. 