Sizing
What size solar inverter do I need for a South African home?
Most busy SA family homes land in the 5–8 kW hybrid inverter class; smaller flats may suit ~3–5 kW; large homes, three-phase supplies or EV charging often need 8–12 kW+. Match continuous backup rating to essential loads, and leave headroom if you will add panels, a heat pump or an EV charger later.
Updated 26 October 2026 · Illustrative ranges — not a formal quote or legal advice.
Answer first: Most busy SA family homes land in the 5–8 kW hybrid inverter class; smaller flats may suit ~3–5 kW; large homes, three-phase supplies or EV charging often need 8–12 kW+. Match continuous backup rating to essential loads, and leave headroom if you will add panels, a heat pump or an EV charger later.
Inverter kW vs battery kWh
Inverter size = how much power you can run at once (kW). Battery size = how long you can run (kWh). A 5 kW inverter with a tiny battery still browns out quickly; a huge battery on a 3 kW inverter cannot start heavy loads. Pair with Stage 6 battery sizing and do I need a battery?.
| Home profile | Often-seen hybrid class | Watch-outs |
|---|---|---|
| Flat / small townhouse | ~3–5 kW | Still need SSEG/CoC if grid-tied |
| Typical suburban family | ~5–8 kW | Essential-load list vs whole-house ambition |
| Large home / borehole / workshop | ~8–12 kW | Surge loads (pumps, compressors) |
| EV wallbox + big daytime loads | ~8–12 kW+ or load management | 7.4 kW charger is continuous — solar EV |
Single-phase vs three-phase
Many suburban homes are single-phase. Townhouse clusters, large estates and light commercial sites may be three-phase — which changes inverter choice and EV charger options. See single vs three-phase and three-phase EV. Paying for three-phase hardware your car cannot use is a common quote trap.
MPPT and DC/AC ratio
More panels than inverter kW (DC oversizing) is normal within manufacturer limits — but string Voc on cold Highveld mornings must stay inside the MPPT window. Demand a string map: MPPT, panel count, roof space.
Hybrid vs string
Pure string inverters are cheaper upfront but go dark in load shedding. Most SA homeowners who want backup choose hybrids — hybrid vs string, solar in shedding. NRS 097-2-1 type testing is non-negotiable for grid connection — NRS 097, approved list FAQ.
Savings framing
An undersized inverter that clips every sunny midday wastes panels you already paid for; an oversized unit that never sees its loads wastes capex. Size from simultaneous loads and bill, then confirm against roof Wp. Retail kWh avoided at ~R3.30–R4.70 still dominates payback versus modest feed-in (tariffs, payback).
Quote checks
- Continuous and surge backup ratings for the essential board
- Exact model + NRS certificate
- MPPT count and string assignment
- Headroom note for EV / heat pump — whole-home
- CoC and SSEG included — CoC
Essential-load audit (do this before you buy kW)
- List circuits that must survive shedding (lights, fridge, router, gate, medical).
- Add running watts and note motor start-up surges.
- Compare to continuous and surge ratings on the inverter datasheet.
- Only then decide whether whole-house backup is realistic or fantasy.
Geysers and ovens on the backup board are how “8 kW” systems feel small.
Parallel and modular options
Some brands allow paralleled inverters for growth. That flexibility costs more upfront but can beat a rip-and-replace when an EV arrives. Confirm firmware, battery bus and NRS documentation for the parallel configuration — not only the single-unit brochure.
Quick FAQ
Is a bigger inverter always more efficient? No — lightly loaded units can waste standby power; match the load.
Can software limit output for SSEG caps? Sometimes — get the setting and the municipal rule in writing.
Should the EV charger have its own inverter? No — it is usually an AC load on the house / hybrid output with load management.
Clipping, export limits and honesty about kW
An inverter that reports midday clipping while the battery is already full and the geyser is off is telling you the array outruns conversion or local loads. Sometimes that is acceptable DC oversizing; sometimes you under-bought AC capacity relative to ambitions (EV + heat pump). Review a month of logs before ordering a second unit. Municipal export caps can also force software limits below nameplate — confirm how that interacts with your SSEG approval (max kW).
Noise, placement and ambient heat
Inverters dislike sealed hot cupboards. Give them ventilation, weather protection and service access. Highveld summer plant rooms cook electronics; coastal humidity attacks poor enclosures. Placement mistakes shorten life faster than brand debates. Follow clearances in the manual and keep battery chemistry requirements in mind for shared rooms.
Brand-agnostic buying filters
- NRS 097-2-1 certificate in hand before deposit
- Local warranty process with a named SA entity
- Proven battery allow-list matching the pack you want
- Monitoring that you can export (CSV/API) for your own records
- Spare parts lead times measured in weeks, not “import TBD”
People’s-choice battery context on this desk points to Solar MD among packs we compare when longevity evidence matters — always verify the live SA warranty sheet. Inverter brand pick should follow compliance and service, not social-media heat. Soft wholesaler context when sourcing: wholesalers.
Worked headroom example
Essential board peaks at 2.8 kW continuous; daytime house baseload 1.5 kW; planned EV charger 7.4 kW but load-managed to keep import under 7 kW. A 5 kW hybrid may cover backup beautifully yet force the EV onto grid-only with aggressive throttling. An 8 kW hybrid eases simultaneous solar + charger operation. Neither number is universal — it is arithmetic from your board. Bring clamp-meter measurements if an electrician already visited; guesses inflate invoices.
Three-phase imbalance warning
On three-phase supplies, dumping a large single-phase hybrid on one leg can trip imbalance protections or annoy the distributor. Some designs use three-phase hybrids or carefully allocated loads. If your quote is silent on phase allocation for an estate three-phase feed, ask. EV chargers on one phase compound the issue — coordinate both in the same single-line diagram.