Electrical safety
Solar cable sizing in South Africa — what homeowners should ask
Cable size is about current, length and heat — undersized cable wastes power and can become a fire risk. Homeowners should not pick mm² from a blog and self-install. Ask your installer to confirm UV-rated PV cable on the roof, correctly sized AC tails, and protection devices that match.
Updated 26 October 2026 · Illustrative ranges — not a formal quote or legal advice.
Answer first: Cable is not a place to “save” R800. Voltage drop steals generation every sunny hour; overheating steals houses. Your job is to ask competent questions and refuse vague answers — not to redesign the loom.
DC PV side
Use purpose-made UV-resistant PV cable, correct connectors (crimped, not pliers-hacked), and routes that avoid sharp tile edges. String current and fuse ratings must match module datasheets — MPPT.
AC side
Inverter to DB tails follow SANS 10142 practices for current-carrying capacity, grouping and installation method. Long garage runs need upsizing for voltage drop.
Battery cables
High current DC between pack and hybrid needs short, correctly lug’d, protected conductors. Loose lugs are a classic thermal failure.
EV interactions
Wallbox circuits are separate designs — EV wiring, power levels.
Questions for the installer
- What mm² on DC strings and why?
- What mm² on AC tails and calculated drop?
- Connector brand and crimp tool calibration?
- Surge and fuse coordination — SPDs?
Red flags
Speaker wire on DC, household twin-and-earth on the roof, no strain relief, no labelling.
SA caveats
High ambient temperatures derate capacity — designs should say so. Educational only.
Quick FAQ
Can I reuse old geyser cable? Almost never for PV DC.
Do aluminium tails appear in homes? Rare — ask explicitly if proposed.
Who signs it off? Registered person on the CoC — CoC.
How to read a quote without getting lost
Demand a single-line diagram, a clear labour vs hardware split, and the assumptions behind any payback number. If savings assume crisis-era tariff hikes forever, re-run the model flat. Ask what happens if export credits fall or fixed network charges rise at the next July schedule. Keep emails — verbal promises about municipal approvals evaporate when staff rotate.
Money first, then resilience
Size for self-consumption and tariff reality, then layer enough battery for the outages you actually live through. A slightly smaller compliant system that is registered and monitored beats an oversized grey-import stack that never finishes SSEG. Compare at least two installer packs on the same load profile.
Putting this advice to work in a South African suburb
Start with last winter’s municipal bills and a simple spreadsheet: kWh imported, fixed charges, and any estimated kilometres if an EV is in the picture. Walk the DB with a registered electrician before you fall in love with a hardware brand. Confirm whether your roof needs structural sign-off and whether the estate has rules about visible conduit. If solar is part of the plan, decide export vs zero-export early because meter changes and prepaid migrations (especially City Power exporters moving to TOU conventional) alter the savings story. For batteries, insist on LiFePO₄ chemistry for home cycling unless you have a specialist reason otherwise, and read usable kWh and warranty throughput — not only the sticker kWh. For EV charging, default to a ~7.4 kW Type 2 wallbox with load management on a dedicated circuit and a CoC. Use public DC for travel corridors, comparing live app rates (DriveElectric’s documentation of SAEV Richmond near R3.49/kWh versus GridCars near R7.35/kWh is a reminder that prices diverge). Keep Stage 6 cover sized to essentials first; do not empty the house battery into the car unless the system was designed that way. Re-check July tariff annexures every year. None of this is glamorous — it is how SA households keep more rand while staying on the right side of SANS 10142, NRS 097 and municipal SSEG desks.
If you only remember four numbers from the wider Solar News 24 desk: metro export credits roughly 108–185 c/kWh incl. VAT in 2026/27; home EV energy often R53–R85 per 100 km at typical residential rates; wallbox all-in often R17k–R35k+; and NERSA’s ≤100 kW distributor registration vs above-100 kW NERSA path. Everything else is detail that belongs on your quote checklist and in your document folder.
Field notes from SA installs
Monitor the system weekly for the first month. Unexpected grid import at midday usually means clipping, shading, a breaker trip, or an EV schedule fighting the battery. Unexpected export with a large evening bill means self-use settings need work. Photograph nameplates before the scaffolding leaves. Label isolators in plain English for family members. Keep spare fuses and the electrician’s number in the DB door. Revisit the municipal tariff PDF every July even if nothing else changes — fixed charges move quietly.
Savings framing for this decision
Metro residential export credits in 2026/27 sit near 108–185 c/kWh incl. VAT (Cape Town ~152.93, City Power 143.29, Tshwane ~108.25, eThekwini ~184.60) while imported kWh often cost several rand. Designs that raise self-consumption beat designs that chase export. Fixed network charges remain after solar — model them. EV households should price home AC charging (often roughly R53–R85 per 100 km at typical residential rates) separately from public DC (often ~R6–R8/kWh, with documented outliers such as SAEV Richmond ~R3.49/kWh vs GridCars ~R7.35 per DriveElectric).
Compliance framing for this decision
Grid-parallel systems need NRS 097-2-1 type-tested inverters, a CoC to SANS 10142, and usually SSEG registration with the distributor (≤100 kW) or NERSA (above). EV wallboxes need dedicated circuits and registered-person commissioning (SANS 10142-1 clause 6.16.8 context in the Ed. 3.3 draft enquiry text). Skipping paperwork to “save time” is how projects stall at the municipal desk or fail insurance scrutiny.
Stage 6 framing for this decision
Size usable battery kWh to essentials (lights, connectivity, fridge, selected plugs) before luxury loads or EV charging on the backup bus. A 5–15 kWh usable LFP band covers many suburban essential scenarios depending on hours and whether PV can recharge between stages. Do not empty the house battery into a car unless the hybrid was deliberately oversized for that behaviour.
Quote hygiene
Require a single-line diagram, labour vs hardware split, NRS certificate PDFs, warranty PDFs, and written SSEG responsibility. Photograph the DB before works. Keep serial numbers and app credentials in one cloud folder. Re-read municipal tariff annexures every July.
Putting the wider desk numbers to work
Four recurring figures: export credits ~108–185 c/kWh incl.; home EV energy often R53–R85/100 km; ~7 kW wallbox all-in often R17k–R35k+; NERSA ≤100 kW distributor path. Use them as sanity checks when a salesperson’s spreadsheet drifts into fantasy. Compare two compliant quotes on the same load profile rather than hunting grey-import bargains without support.
Practical next steps (1)
Write down your tariff code, last 12 months of kWh, main breaker size, and roof photos. Send the same pack to two installers. Ask each to state usable battery kWh, export assumptions, and whether prepaid migration applies. For EV add-ons, confirm load management and CoC line items. Schedule estate approvals before scaffolding. After commissioning, verify monitoring for a full sunny week and one shedding evening. If numbers diverge from the quote model by more than a little, call the installer while retention is still open.