Guys and gals.
What are your thoughts on a hypothetical financial decision?
If I need more panels, say R20k for that.
How long will it take to spend R20k on Eskom if I use Eskom during the day to top-up the bank, using that power at night?
10 units per day @ R2 = R20 per day (for your monster bank ;))
20*30=600 per month
Over 10 year payback assuming no increases (big if) - but no more load shedding for you.
I opened the taps for shiits and giggles and saw 101amps at one stage when the sun came through the clouds. 70amps(?) from Eskom:
So I wondered … peak sun hours, “laat waai” = more usage at night, slight offset ito losses (?), but R20k+ worth of losses?
What IS awesome … the cells take it like champs. No driver installed, just Victron doing its thing.
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You need more panels… Now is a good time before prices go up again!
I believe in more panels before batteries, inverters MPPT’s everything.
Today was such a day, load-shedding and lousy weather in KZN.
I am in between batteries at the moment.
I have just repurposed 4 x 12V Trojans out of a golf cart as a temporary bank.
But because I have 83 panels up I can still supply the 5kVA Phoenix and keep them charged for my mother’s house when it is raining.
When it’s sunny I can supply my sister’s guest house next door.
We all, me included, say that.
Do we ever have enough panels?
Here is the thing, I may sell 16 cells in a few months’ time, hence the hypothetical question.
Unless your name is @Gman … even he is not done yet. 
How do you pay R2/kWh? It’s over R3 here, and about to go up by another 10%
My bill last month: R78 incl VAT = 53 units
Fixed Charge: R264.97
R2.65 ish/kWh, where I am in KZN, and about 4K p.m fixed charge. (100kVA 3ph supply)
Edit: Before the next increase.
A panel watt saved about a cent per day on average in February.
(But I never have production curtailed).
I wish I had those rates
R2.45 incl and R196 per month.
That is for <600 units pm.
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Ssshhhhhh!!! I got another hobby I need to feed now, but the itch is there to get 10kwh storage more on top of my 35kwh. At 10am in the morning i’m basic fully charged, so need something to keep the panels busy. 
I need to put up a car-port to, 6m by 11m and well well, i think panels will fit nice there, more power for the EV vehicle that I want to get 
because driving 74km to work and back with the fuel price isn’t going to work for me.
At R2.45 per kWh his R20k is 8163 kWh. R20k buys you in the region of 2.7kWp, which needs 3023 full sun hours to reach the target. Let’s say, conservatively, he gets 5 sun hours per day (or whatever the technical name for it may be) it’ll take 604 days (basically 20 months) to reach breakeven.
I would go for 1208 days (40 months) min to break even due to winter and global weather changes after the last winter’s experiences.
BUT … the question has been answered. Thanks @Speedster and @mmaritz
Right, we missed something. The sums @Speedster and @mmaritz did, is technically correct.
It will “cost” ± 604 days (basically 20 months) to reach breakeven on R20k.
But my question was more detailed i.e. “… using that power at night?”
So yes, if I ONLY charge the bank with Eskom and never use that power, then it can cost R20k … but I’m using the power at night again.
The actually “sum” is more “challenging”:
- The losses from Eskom to Lifepod4 bank. Lead-acid was like 30% losses, Lifepo4 is what? 1%?
- Then back from Lifepo4 bank back to AC at night. I care not about inverter inefficiency, I lose that already.
Cause my gut, and it has been wrong, says that in the above scenario, it will take a very long time to get to R20k spent on more panels, if the "losses"from Eskom to DC - DC to House is low.
Any more thoughts on that?
Ps. Yeah, I know, TTT always comes with sidebars, new “moves”, out-of-that-“other”-box ideas that sometimes are crap, now and then they make people sit up and think … maybe this is one of them. 
Sometimes we have to STOP SPENDING more on our WANTS / NEEDS /HOBBIES.
Dude, your posts are very hard to read. Or perhaps I’m just in a hurry and want to get to the point quickly. What on earth are you trying to do? Charge from the grid and use it at night? Why?
In one or two sentences, please explain the use case.
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The losses are virtually negligible, but make it 10%. Then we’re up to 660 days, 14 months. The panels aren’t the cost, it’s the battery to store all that energy for overnight usage.
Agree Plonkster
Just work out the saving if you DONT have to use Eskom. ie More panels to charge battery during the day and use at night.
Wife says: Use your words more.
Plonkster says: Use fewer words.
Like top-up 5kWh into the bank using Eskom, then draw that 5kWh out again tonight.
What are the losses on Lifepo4, if lead acid was like ±30%?
It depends on how you charge them. Directly from the PV probably small and then 10% on DC → AC conversion. Charging from AC and discharging to AC probably 20%?
I think how quickly you dis/charge them also impacts. Faster dis/charging rates increase internal resistance and therefore losses to heat?