If you want suggestions for more useful calculators see this site https://blinkcalc.com/. There could be some if then customised to SA we may here find particularly useful
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Had a look at that site, some of it is lekker but most is generic. For us here in SA the useful ones would be practical farm and household stuff. A solar payback calculator that works with our Eskom tariffs and load shedding, that I would use tomorrow. Also a diesel cost per km for the bakkie, and a borehole pump running cost on solar versus generator. Feed cost per animal also handy when maize price jumps around.
People dont need fancy, they need numbers that match our prices and our rands. Keep it simple and local, dis mos so.
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Agreed only a selection would deserve or be necesary to localise to our day to day decision dilemmas we face
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Johan’s onto something with that solar payback one. I’ve sorted my own setup years ago and the maths people quote online never matches reality here, because they leave out the load shedding factor and the way our tariffs jump once you cross into the higher block. A proper SA calculator would need to take your actual municipal tariff, your inverter and battery size, and how often the power’s actually off, otherwise the payback figure is just a fairy tale.
The borehole pump one Johan mentions is clever too. I’ve wired a few of those and people are always shocked how much a pump pulls on startup, that surge is where the generator chokes and the solar setup needs proper sizing.
One thing I’d add from experience, build in a panel degradation figure and a battery replacement cost down the line, because that’s what kills the rosy numbers. A calculator that’s honest about that would actually be useful instead of just selling you something.
Between you and Johan you have basically written the spec for me here MarkD. The honesty points are exactly why most of these calculators are useless. A payback number that ignores panel degradation and a battery swap at year eight or ten is just marketing, so I want those baked in from the start rather than bolted on afterwards.
The way I am thinking about it, you put in your actual municipal tariff including the step once you cross into the higher block, your panel kW, your inverter and battery size, and roughly how often your area is off. Out the back it gives a payback range instead of one hero number, with a low case that assumes degradation and a replacement battery, and a better case if your area still sheds a lot. That way nobody walks away with a fairy tale figure.
The borehole surge point is a good catch too. Most people size for running watts and forget the startup spike, so I will flag that the inverter and battery have to carry the surge, not just the steady draw. Were the pumps you wired on soft starters, or just straight direct on line? That changes how brutal the surge sizing has to be.
This one is going on the build list. Give me a bit of time to get the tariff data right per municipality, because that is the part everyone fudges and it is exactly where the numbers go wrong.
Right MarkD, this one is live: Solar Savings & Payback Calculator South Africa
I took your honesty points straight into it. It shows the optimistic payback an installer quotes next to the realistic one, then lists exactly what eats the gap, the wasted daytime power, panel ageing, the battery replacement down the line, and the higher fixed charge some municipalities add once you go solar. Export credit defaults to zero, because most places pay nothing for what you push back unless you are registered.
Have a proper play and tell me if the self consumption side feels right to you, since you have actually sized these setups. To keep it out of Nebula’s thread I started a dedicated one for it here: New tool: an honest solar payback calculator for South Africa