Safety & standards
What is islanding and anti-islanding for solar in South Africa?
Islanding is when your inverter keeps a portion of the house energised while the municipal grid is dead; anti-islanding is the protected behaviour that stops your system from back-feeding a dead grid and endangering utility workers — required under NRS 097-style grid code expectations for SSEG. Homeowners want intentional islanding for load shedding backup; metros want anti-islanding toward the grid. Good hybrids do both, on separate logic.
Updated 27 October 2026 · Illustrative ranges — not a formal quote, credit decision or legal advice.
Answer first: Backup power during Stage is an intentional island on your essentials board. Exporting into a dead street cable is the dangerous island regulators forbid. Your handover should show that the hybrid detects grid loss, disconnects from the grid cleanly, and only then powers the backup circuits.
Two different “islands”
| Mode | What you want | What metros forbid |
|---|---|---|
| Intentional island (backup) | Lights, fridge, router on battery/PV while grid is off | — |
| Unintentional island (grid side) | — | Energising the dead municipal feeder |
NRS 097 family documents and metro SSEG rules expect listed inverters with proven anti-islanding. DIY “grid-tie without protection” kits are how CoC and insurance stories end badly — NRS 097 · approved inverters · DIY risks.
How hybrids usually behave
- Grid present: sync, import/export per settings and CT clamps — CT clamps · export limits.
- Grid fails: disconnect from grid, form a local backup supply for labelled circuits — solar during shedding · essentials.
- Grid returns: verify stability, then reconnect per OEM timers — do not defeat this with illegal bypasses.
Generators and dual supply
Adding a genset without interlock or hybrid genset input can create unsafe paralleling. Changeover / ATS labelling and dual-supply notices matter at inspection — generator interlock · ATS · dual-supply labels.
What to ask on commissioning
Watch one simulated outage: backup loads stay up, non-backup goes dark, and a loop tester / installer proof shows the grid terminals are isolated. Photograph settings. Related: inspector tips · inspection fails · CoC.
Document pack to keep with this answer
Store serials, SoC/export screenshots, SSEG references and the metro meter appointment beside your CoC. Future installers and buyers argue less when the folder is complete — read a quote · selling with solar · warranty transfer.
Why utility workers care
A dead MV/LV feeder is assumed safe after isolation. A rooftop inverter that keeps energising that feeder through a transformer is a lethal surprise. Anti-islanding (voltage/frequency windows, ROCOF, active methods — implementation varies by OEM) is why listed SSEG inverters disconnect from the grid side quickly when the network fails.
Your backup loads can still run because the hybrid opens the grid-side contactor and forms a local supply — that is intentional islanding on your side of the break. Related: solar during shedding · UPS vs hybrid.
Tests worth watching at handover
- Pull the main / simulate outage: backup board stays up; street side dead.
- Restore grid: reconnect delay matches OEM docs (often tens of seconds).
- Export limit and CT direction still correct after the test — export limits.
- Labels: dual supply / embedded generator notices visible for inspectors — dual-supply labels.
Illegal workarounds to refuse
Hard bypasses that parallel a genset with the grid, “always on” export hacks during Stage, or non-listed grid-tie kits without protection void CoC, insurance and SSEG. If a quote depends on defeating anti-islanding, walk away — red flags · DIY risks · inspection fails.
Microgrids and estates
Estate or commercial microgrids need engineered protection studies beyond a single residential hybrid. Homeowners in HOAs should still keep household anti-islanding intact even if the estate has a larger BESS story — estate / HOA · commercial BESS.
Field notes for what is islanding anti islanding sa
Bring this page to the commissioning visit. Ask the partner to demonstrate the behaviour described here, photograph the settings, and store them with the CoC and SSEG reference. When a future technician inherits your plant, that folder beats a WhatsApp voice note — choose installer · read a quote · selling with solar.
Also keep metro tariff PDFs and OEM warranty sheets dated. News headlines and brochure stickers age; annexures decide disputes. Cross-check fixed charges after SSEG so savings models stay honest — fixed charges · 2026/27 tariffs · metro tariffs hub.
NRS 097 framing for homeowners (plain language)
You do not need to recite protection algorithms. You need a listed inverter, a CoC, and a commissioning demo that proves grid-side isolation during outage. Metros lean on the NRS 097 family and their own SSEG rules to keep embedded generators from back-feeding dead networks. Ask for the certificate or type-test reference the installer will attach to your file — NRS 097 · approved inverters habit · SSEG.
Hybrid settings that matter for safe islanding behaviour include: grid-loss detection sensitivity (within OEM limits), reconnect timers, backup board mapping, and generator interlock mode if a genset exists. Changing those after a DIY YouTube session is how inspections fail — generator interlock · inspector tips.
- Label the changeover / hybrid so the next electrician sees dual supply immediately.
- Never bridge grid and backup neutrals in ways the OEM forbids.
- After SPD or DB work, re-run an outage test before you trust Stage 4 night.
- Document firmware versions — protection logic rides on software as much as contactors — firmware.
If you add EV charging, ensure load management cannot force a grid-side fault during islanded operation; many wallboxes should simply stop when the grid reference disappears — EV load management · EV CoC.
Homeowner myth-busting
Myth: “Anti-islanding means I cannot have backup.” Fact: it means the grid terminals go dead; your labelled backup board can still run. Myth: “Zero-export equals no protection needed.” Fact: zero-export is a power-flow setting while the grid is up. Myth: “A plug-in UPS is the same as a hybrid island.” Fact: UPS boxes cover plugs, not compliant SSEG paralleling — UPS vs hybrid · zero-export · essentials.
Keep a one-page diagram showing grid in, hybrid, backup board, non-backup board, and any genset interlock. Inspectors and future buyers both thank you — labels · selling with solar · CoC.
Commissioning photo set
Photograph grid-side isolator state during a simulated outage, backup board live loads, dual-supply labels, and the inverter screen showing island/backup mode. Store beside the CoC. That pack ends “it used to work” debates after firmware changes — firmware · inspection fails · install timelines.
Related reading: solar during load shedding · generator interlock · NRS inverter habit · CoC explained.
Grid-side dead, house-side alive — the intended picture
Anti-islanding stops your inverter energising a utility feeder that workers assume is dead. Your hybrid still forms a local island on the backup board by opening the grid contactor. Confusing those two “islands” is how homeowners argue with inspectors — solar during shedding · UPS vs hybrid · NRS 097.
Generator parallels are a different hazard
A genset hard-paralleled to the grid without interlocking is not “extra backup”; it is a CoC and safety failure. Use a listed changeover / interlock path — generator interlock · changeover ATS · diesel vs battery.
Estate microgrids
HOA or commercial microgrids need engineered protection studies. Your household hybrid must still anti-island correctly even if the estate tells a larger BESS story — estate / HOA · commercial BESS · sectional title.
Firmware and settings drift
After OEM updates, re-run the kill-main test. Export limits and reconnect timers sometimes reset — firmware · export limits · DC isolation / labels.
Quick questions
Is islanding illegal?
Unintentional grid-side islanding is what anti-islanding prevents. Intentional backup islanding on your side of the transfer is the normal hybrid feature — when listed and installed correctly.
Do UPS plug-in units anti-island?
Consumer UPS boxes are not SSEG generators in the metro sense; they also will not run your DB. See hybrid vs UPS answers before you mix stories.
Can I disable anti-islanding to export during shedding?
No — that is unsafe and non-compliant. Export needs a live, coordinated grid.
Does zero-export remove anti-islanding needs?
No. Zero-export limits power flow when the grid is up; anti-islanding still protects workers when the grid is down.