A string inverter quote should carry, as separately priced lines, the inverter with its exact model and firmware revision, the DC string design with its isolator, combiner and surge protection, the AC protection and cabling to the distribution board, the mounting structure and fixing method for the stated roof covering, the labour, the Certificate of Compliance, and the SSEG application with the name of whoever lodges it. The four items most often buried inside one "supply and install" total — the DC isolator, the CoC, the exact model and firmware, and the structural assessment — are also the four you cannot uncover until after the deposit has cleared.
You are sitting where I was on a Tuesday evening: three pages of quote open on the laptop, and somewhere on page two the entire system reduced to one line. Panel count? "Included." Orientation? Not mentioned. The rest of the page is a total, a deposit request and a banking detail. The kettle goes on, and the only question worth asking is what, precisely, is included in "included".
I have since stood in enough passages with a torch to know the answer. Usually it is a bakkie load of fittings bought on the morning of the job, and the things that were never priced are the things you only meet once you have already paid. So here is the quote taken apart, in the order the problems actually arrive.
The single line, and why it makes the quote incomparable
A bundled figure cannot tell you what you are buying. Two installers can both say "6 kW system" and mean entirely different roofs: one is 6 kWp of panels behind a 5 kW inverter, the other 8 kWp behind a 6 kW inverter. That ratio of DC array size to AC output decides how the system behaves on a clear Highveld morning and how hard the inverter works at midday. It is also a number you cannot back out of a lump sum, so comparison collapses into comparing totals, which is exactly what a lump sum is built to make you do.
The fix is not confrontational. Ask for the same system described twice, once as equipment and once as work. A supplier who knows their product will do it without drama, and the ones who resist are telling you something.
The DC side is where the surprises live
The inverter is the only part of a solar installation that arrives in a branded box with a manual. Everything upstream of it is loose stock: string cable, connectors, a combiner, a DC isolator, surge protection, glands, conduit, labels.
On the DC side, the quote should say whether there is one string or two, what the array voltage works out to on your coldest morning, whether a combiner box is included, and where the DC isolator sits. That isolator is small and unglamorous and it is the single most common thing missing from a lump-sum quote. It also happens to be the switch someone needs to make the roof safe, which is why the standard the installation is measured against expects a means of isolation on the DC side and correct labelling at the board.
I have watched a DC isolator arrive in a plastic packet on day two, bought from a wholesaler because nobody had priced it. That alone is not a disaster. It becomes one when the rail has already been cut and the cable run is thinner than the string design called for, because the person buying stock that morning was not the person who designed the string.
The model number is a municipal question before it is a technical one
Here is where a lot of quotes get it wrong in a way that costs real time. The model on the quote is not a preference; it decides whether the system can be registered at all.
Municipalities work from an approved inverter list for grid-tied connection, and approval is usually tied to a specific model and sometimes to specific behaviour such as export limiting. Suffixes matter. A model ending in a letter the list does not carry is a different model as far as the application is concerned, and unless the quote says otherwise, that becomes your problem and not the supplier's.
The firmware line gets laughed at until it bites. Some approval conditions assume the inverter can hold export at zero or be set to a particular grid code, and a unit that shipped with older firmware and was never updated may not do what the approval assumes. I now want the firmware revision on the paper, and I want to know who updates it and when. If it is missing, it becomes a conversation in a passage six weeks later.
Who lodges the SSEG application
An SSEG application is administrative work with a queue. Somebody has to compile the diagram, the inverter datasheet, the CoC and the commissioning sheets, submit them, and answer when the inspection or meter swap is scheduled.
The quote should name that somebody. Not "we handle all paperwork" in the footer, but a line. Is the application included, is the municipal fee carried by the installer or passed through to you, and what happens to the price if the inverter you chose turns out not to be approved. That last question separates a salesperson from an installer. What you want back is a stated consequence, not reassurance.
The roof and the board are assessed before the price is fixed
Roof covering and roof age change the job. Concrete tile is one thing, aged clay tile another, IBR sheeting another again, and a roof near the end of its life is not a roof you bolt rails onto without saying so. The fixing method should be named: hook, strap or bracket, and how the penetration gets sealed.
The distribution board is the second half of that assessment. Is there physical space for the breakers? What condition is the board in? Is the earthing what it should be? Older South African homes sometimes have a board that needs work before anything can legally be added to it, and that work belongs on the quote as a line, not in a phone call on the day.
An assessment that happens after the price is fixed is not an assessment. It is a variation.
The CoC is a document with a name against it
The Certificate of Compliance is issued by a registered person who is accountable for the installation, and it is not a formality tacked on at the end for free. It should be a line item, with responsibility stated, and the quote should be clear about whether it is issued on completion or held back until the municipal inspection.
While you are there, ask who signs it and whether that person is doing the AC work. It is a fair question and it is usually answered honestly.
What the paper looks like when it is done properly
Not longer. Just more specific. Inverter model and firmware revision, string count and array size, DC isolator and combiner, surge protection on both sides, AC breaker and earth leakage, cable sizes, rail and fixing method, labour, CoC, SSEG application with a name against it, and a line stating what changes if the model is not approved.
None of this is a demand for free engineering. It is a demand that the price you are asked to pay a deposit against describes the same system that will end up on your roof. The gaps in a lump sum do not disappear. They move. They move to the morning the bakkie arrives, when the deposit is already in someone else's account and the only lever left is a phone call.
