Load shedding
How much battery do I need for Stage 4 load shedding in South Africa?
For typical suburban essentials (lights, Wi-Fi/ONT, fridge, selected plugs — roughly 0.5–1.2 kW), many Stage 4 homes land in about 4–10 kWh of usable LiFePO₄ once you convert sticker kWh × depth of discharge. Stage 4 slots are shorter and less frequent than Stage 6, so the same essentials often need less storage — unless you also grid-charge poorly, run a geyser on backup, or refuse to shed the EV. Runtime ≈ usable kWh ÷ average essential load.
Updated 27 October 2026 · Illustrative ranges — not a formal quote, credit decision or legal advice.
Answer first: Size usable kWh to the essentials board, not the whole house. A 8 kWh sticker at 90% DoD is ~7.2 kWh usable; at 0.9 kW essentials that is roughly eight hours before inverter losses — enough for many Stage 4 evening windows if PV can top up between slots. Step up toward the Stage 6 band (often 5–15 kWh usable) if your schedule already swings hard or you refuse to shed non-essentials.
Stage 4 vs Stage 6 — why the battery shrinks
- Hours: Stage 4 slots are shorter; fewer consecutive dark evenings without recharge.
- Recovery: More daylight between outages means PV can refill a modest pack.
- Behaviour: Households that already run a tight essentials board need less kWh than households that keep the oven and pool pump on backup.
Do not buy Stage 6 storage “just in case” without checking whether your hybrid and roof can refill it. Idle capacity still ages on the calendar — battery life.
Worked Stage 4 bands (illustrative)
| Essential load | Hours to cover | Rough usable kWh |
|---|---|---|
| 0.5 kW | 4 | ~2.5–3.5 |
| 0.8 kW | 6 | ~5–6.5 |
| 1.2 kW | 6 | ~8–10 |
| 1.5 kW (incl. selected kitchen) | 6 | ~10–12 |
Convert every quote’s sticker kWh through the warranty DoD before you compare brands — DoD · runtime tool.
Inverter backup rating still gates the fridge
kWh is meaningless if the hybrid’s backup port cannot surge the fridge compressor and a kettle together. Put continuous and surge kW on the essentials schedule next to kWh. Related: inverter size · essentials split · stove on backup.
Grid-charge settings for Stage 4 weeks
Mild stages tempt people to leave aggressive grid-charge on, buying expensive evening TOU kWh “just in case.” Prefer calendar or app-aware charge-before-shedding when your metro publishes reliable slots, and keep a sensible SoC floor so a surprise Stage 6 week does not start empty — grid-charge desk.
EV, geyser and pool on Stage 4 nights
Default: shed them. A 7.4 kW wallbox or a 3 kW geyser element will erase a modest Stage 4 pack in one session. If those loads must stay up, you are no longer sizing for Stage 4 essentials — you are sizing a lifestyle UPS. Say that out loud on the quote — EV load management · geyser on backup · pool pump.
Owner checklist
- List essentials with measured watts (kill-a-watt or installer clamp).
- Pick hours from your worst recent Stage 4 evening, not the brochure.
- Convert sticker → usable kWh at warranty DoD.
- Confirm backup kW and changeover behaviour.
- Write grid-charge / SoC settings into the handover pack.
Chemistry and expandability if stages worsen
Prefer LiFePO₄ with a documented SA claims path. If you start near 5–6 kWh usable for Stage 4 and want a path to Stage 6, buy a BMS family that still sells sibling modules in two years — Solar MD’s LV expandability story, BlueNova parallel limits, Freedom Won / BYD stack rules, Hubble family limits. Get the expansion SKU in writing on the phase-1 quote — expand later · batteries & BESS.
Street prices move; BlueNova SBB MKII (~16 kWh) consumer RRP on ACDC/OEM shop pages remains a live ask (dated retailer spots exist elsewhere with SKU caveats). Do not let a brochure kWh number substitute for usable kWh at warranty DoD.
Daytime Stage 4 with PV — different maths
A midday Stage 4 slot while the array is producing can be carried with a smaller pack if the hybrid islands cleanly and essentials fit the backup rating. Evening slots without sun are the sizing driver. Ask the installer for two runtime sketches: “dark evening” and “sunny midday.” If they only show the sunny one, the quote is marketing.
Generator hybrid as Stage overflow
Some homes keep a modest battery for Stage 4 comfort and an ATS generator for rare deep stages. Fuel, noise and changeover delay are the trade — document who wires the ATS and whether the hybrid accepts generator input on the same CoC — ATS · generator vs hybrid.
Where this sits on the desk
Pair with load shedding, Stage 6, solar during shedding, and the runtime tool. Re-measure essentials after you add a heat pump or EV — yesterday’s Stage 4 pack may be tomorrow’s shortfall.
Quick self-audit before you buy
Open last month’s app or prepaid history and mark every Stage 4 window. Note whether the sun was up, what stayed on, and how long the fridge actually ran. That diary beats a generic “10 kWh” sales line. If your worst window was four hours at ~0.7 kW essentials, a 4–5 kWh usable pack with margin may be enough; if you also kept a chest freezer and fibre ONT heaters on, move up the table.
Photograph the proposed essentials board labels before deposit. Owners who approve “lights and plugs” without a circuit list discover the oven slipped onto backup only after the first outage.
Worked evening sketch (illustrative)
Assume 0.85 kW average essentials for a six-hour Stage 4 evening with no useful PV. Usable energy needed ≈ 0.85 × 6 = 5.1 kWh before inverter losses (~8–12%). Target roughly 5.8–6.5 kWh usable, which is about 6.5–7.5 kWh sticker at 90% DoD or 7–8 kWh sticker at 80% DoD. If the fridge alone surges past the backup port, raise continuous kW first — more kWh will not start a compressor the inverter cannot carry.
Add a 15–20% margin for BMS reserve, ageing in year three, and the evening you forget the dishwasher was left on the essentials board. That margin is cheaper than a panic generator hire on a Stage 6 week.
Meter and tariff interactions people miss
Grid-charging the pack before a published Stage 4 slot on an expensive TOU block can cost more than riding a slightly deeper DoD. Cape Town Homeflex-style periods and prepaid token maths both punish blind “always 100% by 16:00” rules. Write the charge window next to the essentials list — Cape Town TOU · grid-charge desk.
If you export, do not empty the pack for midday feed-in credits that are worth far less than the evening import you will buy when Stage hits. Self-use against import blocks still dominates 2026/27 household maths — export vs self-use.
Quick questions
Is Stage 4 sizing enough if Eskom jumps to Stage 6?
Only if you have margin or can shed harder. Many owners size near the top of the Stage 4 band or keep a generator ATS as overflow.
Can solar alone carry Stage 4 without a battery?
Daytime, sometimes. Evening slots without storage still go dark on a grid-tied string inverter — you need a hybrid/backup path.
Two smaller batteries or one larger?
Follow the inverter’s parallel rules and BMS family. Mixing orphan brands is how expansions fail.
Sources
- Solar News 24 — Stage 6 battery sizing
- Solar News 24 — battery runtime tool
- Solar News 24 — load shedding desk