The size of inverter a South African home may connect is capped by the supply capacity the municipality has approved for that property, not by the roof, the battery bank or the budget. SSEG registration documents ask for the machine's rating in kVA, and that figure is measured against the ceiling the municipality sets for your connection. The practical result is that the first number on a solar project is not the panel count or the battery. It is the rating on your main breaker, and the supply capacity the municipality has on record for your erf.
Stand at the distribution board with me. Torch in one hand, because the stamp on that main breaker is small and the plastic around it is old. Sixty amps, or a hundred, or three phases of a size you have never actually looked at properly. That number is the soil the whole system grows in. Any quote that arrives before you have it is a guess with a logo on it.
I have watched this happen in the wrong order more than once. The roof gets measured, the geyser and the pool pump and the stove get counted, a quote comes back with a neat 8 kW hybrid, everyone nods. Then someone opens the municipal application guide and finds a line about how much generating capacity may be connected in relation to the approved supply. That line decides the project. It is not a footnote you deal with at the end.
The limit is written against your supply, not your inverter
Read the guide's wording slowly. It rarely says "you may install an inverter of X kVA". It says something closer to: the connected generating capacity may not exceed a given proportion of, or a given relationship to, the supply capacity approved for the property. The supply is the reference point. The inverter is what gets tested against it.
That matters because your supply capacity has a life of its own, separate from your house. It lives in the municipality's records as the capacity allocated to your erf, and it shows up physically as the main breaker and the cable feeding your board. Those two normally match. They don't always. I have seen a board carrying a breaker bigger than anything the municipality has on record, and I have seen the reverse after a property was subdivided or a flatlet was added and wired in. So before you argue with anyone about inverter size, confirm what the municipality believes your supply is, rather than what you believe it is.
Then there is the other half of the spelling. A single-phase connection at 60 A and a three-phase connection at the same amps are not the same size, because the arithmetic behind the breaker is different. This is one of the reasons the cap feels arbitrary when someone repeats it to you from memory at a braai. It isn't arbitrary. It is just written against a quantity most homeowners have never had to think about.
Why the form asks kVA when the quote says kW
Here is the mismatch that catches people who did everything else right.
Your quote says kW. The brochure says kW. The datasheet, one column to the right, says kVA, and it is a bigger number. The registration paperwork wants the kVA. So do the protection and connection calculations, because the supply deals in current and voltage, which is apparent power, not in the real power doing useful work in your kettle and your geyser element.
As a rough illustration, a machine sold as 5 kW with a power factor of 0,8 to 0,9 lands somewhere around 5,5 to 6 kVA of maximum apparent power. If the ceiling is expressed in kVA and you sized yourself in kW, you can be over the line without ever noticing. Pull the maximum apparent power off the datasheet and use that. Not the number on the front of the box, and not the number the salesperson rounds down for you while you are still deciding.
Not exporting does not lift the ceiling
The assumption I run into most often is that a system with no feed-in, no export, no credit and no intention of ever pushing a single watt up the line sits outside the rules somehow. In many metros it doesn't. Registration is triggered by the presence of a generator that can operate in parallel with the supply, not by whether anything gets sold back during the day.
This is where people start bargaining. The installer says he will set an export limit in the app, or lock the machine to self-consumption, so surely the nameplate kVA stops mattering. Maybe. That is a question for your municipality, in writing, and it is not something I would quietly assume on a Tuesday and hope nobody checks. The application records the rating of the machine that is physically connected. Whether a limited setting changes that in your metro is a question you put to your metro, not to the person selling you the inverter.
If the inverter genuinely never runs in parallel with the grid, the picture usually changes. But that describes an off-grid arrangement, not a hybrid with a grid input and a changeover, and it carries its own costs and its own compromises with it.
When you are over: two doors, and neither opens at the installer
If the intended inverter exceeds the ceiling, there are two honest paths and a lot of dishonest ones.
The first is a smaller installed capacity. Fewer kVA on the wall, which almost always forces a rethink about what runs at the same time. That is an essential load conversation, not a hardware conversation: what genuinely has to be alive during an outage, what can be staggered, what gets a timer or a smaller element. Sometimes the honest answer is that the smaller machine was always enough and the bigger quote was a comfort purchase.
The second is a supply upgrade, which means the municipality is involved before installation, not after. A larger connection may mean a new breaker, new cable, a revised connection agreement and a site visit on their schedule. It is a process that runs on their clock, and it is the reason the ceiling belongs at the front of the project instead of in a queue behind it.
What I would not accept is the bigger machine going onto the wall on a promise that the paperwork will catch up. Once the inverter is mounted and the CoC is signed, you are the one holding an installation that does not match the supply it is attached to.
And count the whole installation, not one box. Two inverters share one ceiling. So does the second one added later, when somebody decides the geyser deserves more.
Certification is a separate gate from size
A registration submission usually turns on more than one thing at once. NRS 097-2-1 covers the interconnection behaviour, the way the machine sits on the grid and disconnects when it should. A Certificate of Compliance under SANS 10142-1 covers the installation itself. Then there is the inverter's own certification status, which is a question about the model rather than the wiring.
So you have two gates, and the machine has to pass both. An inverter that is properly certified can still be too big for your supply. An inverter that is comfortably small can still be unregistrable if the model is not listed or its paperwork is not in order. I have seen people spend weeks solving one of those problems and then discover the other one was never the issue in the first place.
The rule you have to look up is your own
Nothing here replaces the by-law or the application guide sitting on your own municipality's website right now. Metros differ on how they express the ceiling, on whether it is a proportion of supply capacity or a stepped kVA figure tied to connection categories, and on how often they revise it. A number someone quoted on a forum two years ago, in a different province, about a different size of connection, is not a limit. It is a rumour.
Find the section on maximum connected generating capacity, or whatever your metro calls it, and write the sentence down exactly as it appears. Then compare it to the kVA on the datasheet. If the two don't fit, you have found your project's most important constraint before spending a rand on it, which is the entire point of checking it first.
That is why the ceiling gets checked before the roof, the battery and the budget. Not because the paperwork is exciting, but because the number in it decides which project you are actually building.
