Concrete

Hello everyone, I'm intending to install a solar PV system at my property, I started educating myself reading through the forum and learning about volts and amps. It is really a fantastic way to learn and I have already learnt a lot thanks to all the experts and those that recently went through the whole process. I intend asking a lot of dumb questions as I go along in planning my system. 
My first question is around prepaid seeing as it seems to offer the highest return on investment. 
I currently pay R886.98 per month in fixed service & network charges for single phase with an 80A breaker. My monthly use of electricity is around 1200 kWh per month.
My current use since June op to October when the latest CoJ tarifs kicked in, works out to R2.95 per kWh and I worked out that had I been on prepaid, based on the CoJ published rates, that I would have paid R2.52 per kWh and that I would have saved R2,650 in the last 5 months that could have gone towards paying for equipment.
My questions are:
1. Does CoJ allow you to switch to prepaid when you already have a system with panels on the roof that they will see when they come to do an inspection?
2. I based my calculation on the rates below +15% VAT = R2.10 for the first 350 kWh then R2.41 for the next 150 kWh and then R 2.74 above 500 kWh. My question is, is this what you end up paying when you switch to prepaid or do you have to buy electricity through an intermediary ending up more expensive?

3. Is it possible to top up prepaid electricity remotely when you are not at the property or do you physically need to punch in a code on your prepaid meter?
4. Is it possible to see how much prepaid electricity you have left remotely?
5. Can one kickstart the process to switch by email or do you need to physically apply for the switch at their offices.
6. Is the 80 Amp breaker an issue to switch to prepaid? 
Those who have been through this process with CoJ, please assist me with my questions to understand this process better.      

@Bobster. Thanks, I will plan for the impact that you described on my cashflow and will also plan for the extra costs that will be incurred. I did a 12 month simulation based on my historical consumption based on the 2022/23 tarifs for prepaid and post-paid. Prepaid beats post-paid by a margin of R7,100 per year without factoring in the usual increases that will come in July 2023, so it looks like as was the case with your conversion, I will also pay off the costs of the conversion in a few months. I wish that I had done this earlier.
The next step will be to implement some power saving strategies to get the usage down from the  current 1200kWh per month and to install a solar system with a battery that will get the usage down by 850kWh per month to a level of 350kWh per month, the cheapest tier on prepaid which is currently R2.10 per kWh.

This is the type of prepaid meter being installed by CoJ as recent as 21 Nov 2022. This was after a guy I know installed a Synsynk system. It was done some weeks after the new PV system.

I keep 3 handy, even though I'm very unlikely to need them. What I'm saying is that the charging function doesn't work very well. 
What hasn't occurred to me is that this is what is happening to folks. The rechargeable batteries don't charge, they have no grid, the handset thus turns off. If they just unplug it and put in good batteries, and there isn't loadshedding, then they'll be sorted. 
The batteries only have to last a few minutes whilst you key the token in. 

You need to put batteries into the handset thing so that it can run without power and then you can recharge.  Takes 3 x AA batteries if I remember correctly 

I have a different meter. Brand name is Itron. IIRC this was being trialled in certain areas when COJ were still trying to read meters over the cell network. The first bunch they got in couldn't do the job and blamed Cell-C. They then switched to driving all over this suburb with what looked like a bunny ears TV aerial sticking out of the window of their car. That didn't work either, so COJ tried plan B, which was when the Itrons were rolled out. 
Anyhoo, the Itron interface unit has 3 X 1.5V rechargables. The ones it shipped with (no branding) were very good at not holding any charge, so I put in some Duracells. These also don't give more than a few seconds use without grid input, so either they aren't getting charged or the charger is rubbish and wrecks the batteries. This interface unit doesn't plug into the mains. It needs USB power, thus I conclude that it must be communicating with the main meter unit wirelessly.

The problem with running out of units and then finding yourself unable to reload is reported a lot in the next door suburb. Where I live (OK, in my street), people seem to be a bit more proactive as regards checking the balance on the meter. The suburb next door may have a different brand of meter if they were not part of the same trial.

COJ said a while back that they were going to take all the meters out of the boxes built into the house walls and mount them at the top of the street poles where they couldn't be tampered with. Concerned residents asked how they were going to load units onto their meters, and that seems to have been the end of that idea.

I've been on CoJ pre-paid for over 10 years, and it surprises me that more people don't use CoJ pre-paid.
WARNING:
- Not all metro's tariffs are the same - YMMV eg EKURHULENI pre-paid is the same as postpaid.
- some metro's charge a connection/network fee on pre-paid

Tip 1: When installing Solar. ask you installer to add a plug on the feed side for the keypad
[if your keypad is communicating over power lines].

Tip 2: Make sure you install an official metro meter - go direct
There was a scam some years back where scammer would install a their pre-paid meter, and then transfer the Electricity statement to their account.
You would have two meters - CoJ meter and scammer's pre-paid.


Tip3: Load 45 days worth of units on install, and refill back every 30 days.
before solar,  I kept 2000 kWh in my meter and used ~900-1200kWh per month, I would refill back to 2000kWh.
On Solar I now use 200-300kWh per month, so I'm reducing the buffer from 2000 to 600.

Tip4: Buy from an official vendor - I use online banking / banking app.
Tip 5: Once you have Solar, get a timers for your geyser and set the schedule to use Solar to heat water (use geyser as a battery)
Mine is on 10:00am-6pm and 4am-6am
Also timer for pool - only run 9am-3pm
Tip 6: Measure Efergy /Sonoff POW/etc.
@Bobster.
My keypad has a 9V battery, and according to the manual is able to communicate even without any units (I've never run out of units)

 
 
 
 

@Bobster. Thanks, I will plan for the impact that you described on my cashflow and will also plan for the extra costs that will be incurred. I did a 12 month simulation based on my historical consumption based on the 2022/23 tarifs for prepaid and post-paid. Prepaid beats post-paid by a margin of R7,100 per year without factoring in the usual increases that will come in July 2023, so it looks like as was the case with your conversion, I will also pay off the costs of the conversion in a few months. I wish that I had done this earlier.
The next step will be to implement some power saving strategies to get the usage down from the  current 1200kWh per month and to install a solar system with a battery that will get the usage down by 850kWh per month to a level of 350kWh per month, the cheapest tier on prepaid which is currently R2.10 per kWh.

I would save up and get an Efergy (or other brand) monitor. They use a (CT) clamp that goes around the input wire on your DB board - so no cutting. It's a lot easier than installing a smart DB switch. Data gets uploaded to the cloud so you can monitor your peak usage and when you use electricity. It does monitor total demand but you get an idea of which devices (circuits) are using electricity quickly - and can focus on finding inefficient devices. Check your draw, switch on a device, wait 30s and then check the app again.
From experience, it's a very good way to save electricity quickly. You can comfortably say goodbye to tumble dryers, halogen lamps, large pool pumps,3 geysers, etc.
It will also be really helpful to help size your solar system as you have a far better idea of your power usage. Batteries are expensive and to get the most ROI you will want to maximize your power usage during the day.

IF you need to you can take it a step further. A kill-a-watt meter can also help to look at specific devices that operate off a plug. You can also make a power monitoring device using a Sonoff/Shelly/Tuya smart switch. Many of them have power consumption meters and will give more detailed data than a kill-a-wat - just a bit of DIY. I would use a Sonoff IP66 box and you can make a mini extension lead to see the demand profile over a period. Make sure you keep your load (well) below the rated maximum. 

I remember getting rid of a car once. I wanted it off my name AQAP. I employed one of these intermediaries who told me that I had to present in person. So I said "OK... so I pay you fees why?". He said "meet me OUTSIDE at 8:30 tomorrow. DO NOT enter, DO NOT join any queue." So I did, and he marched me into some office, pointed at me and said "here he is. He was here and you've seen him" and the person in the office agreed that I had indeed been present. Then I get told thank you very much, you can go now and we'll call you when the paper work is done.

I should think you'd have to show your face. The City does require that you present in person and that you are verified against an ID document and their records because only the property owner may request a change of tariff and sign all the consent forms.

If you paid a 3rd party and they took care of everything then there is probably a ... gratuity... built into their fee.

One thing you have to be careful of is not running out of units. This occurs all the time where I live. The meter runs out. You grab your phone and buy more units. But now you can't load them because the meter has shut down the supply to your house and isn't talking to the CIU. Apparently there is a way around this, but it's not straightforward. Better to monitor your usage and buy just in time. Remembering that the stepped charges reset on the first of the month, so if it's the 28th, try to buy just enough, not 500 units that will carry over into next month (and they will, but you've paid a higher price for them).

Some hopefully useful feedback for you based on my CoJ conversion to prepaid, as well as other's I'm aware of that have done the conversion in my complex:
1) Yes - they didn't have any problem with it.
2) If you have a prepaid meter directly from City Power, then you buy power at those published rates via Internet Banking etc.
3) Not as far as I'm aware - everything has to happen through the customer interface unit (CIU) which has a keypad and talks directly to the meter.
4) Not as far as I'm aware no - also through the customer interface unit.
5) Emails go into a black hole. There are two options - go to your municipal offices yourself, fill out the forms etc., or get a third party to register on your behalf for a fee (I took the latter approach as I didn't have the time or zen-master levels of patience to deal with council - I can provide details via PM).
6) No - I had the same 80A single phase connection.
FYI - the CoJ prepaid meters supplied, at least in Randburg from the Roodepoort CoJ (African Metering Solutions (AMS) CIU-PH04 since about mid 2022) CIU's use power line communication - i.e. the unit has to have a direct connection via your electrical wiring to the meter. Thus, you either need to manually switch the plug circuit you have the CIU connected to (presumably essential load plug) via a changeover switch back to Eskom to be able to load your prepaid vouchers or see you balance, or you need to have a non-essential/grid-connected plug for the meter that is electrically compliantly wired permanently into Eskom. I'm also aware of at least one instance in my complex where the meter was rather picky as to which plug it would reliably work on, so something potentially also to keep in mind.