Load shedding
Essential vs non-essential loads on a solar backup — South Africa
Hybrid installers often split your DB into essential (battery-backed) and non-essential circuits. That split protects payback: you size storage for high-value loads instead of trying to run the whole house. Typical essentials: lights, Wi-Fi/router, fridge/freezer, modem, selected plugs. Keep geysers, ovens, pool pumps and big ACs off backup unless battery and inverter are sized for them — oversized backup is the fastest way to destroy solar ROI.
Updated 26 October 2026 · Illustrative ranges — not a formal quote or legal advice.
Answer first: The essential / non-essential split is how South African hybrids deliver load-shedding resilience without buying a commercial BESS. Put high-value, low-kW circuits on the backup port; leave thermal monsters on the grid-only side. Outage comfort matters — but bill savings from self-use remains the primary design driver when retail kWh are multi-rand and export credits are roughly 108–185 c/kWh incl. across major metros.
Usually essential
Lighting, ICT, fridge/freezer, security, medical devices (declare these).
Usually non-essential
Geyser element, stove/oven, underfloor, pool, large AC, laundry heat.
Grey area
TV/entertainment and office printers — lifestyle choice; they cost battery minutes fast.
Why the split saves rands
Battery kWh are expensive compared with extra PV panels. A 3 kW geyser element can empty a modest pack in a couple of hours — the same pack might cover lights, router and fridge overnight. Keeping the geyser on a daytime PV-friendly timer or heat-pump strategy protects both comfort and ROI — water heating, heat pump + solar + EV.
Runtime maths
Rough energy: fridge ~1–2 kWh/day, LED lighting + Wi-Fi often well under 1 kWh for an evening, while cooking or heating can be several kWh in a single meal. Use the battery runtime tool and Stage 6 framing — how much battery for Stage 6 — before you insist on “whole house backup.”
DB work and changeover
Creating an essentials DB (or re-labelling circuits onto a backup board) is normal project scope. It may include new breakers, changeover/ATS logic if a generator exists, and labelling so the next electrician does not guess — DB upgrade, ATS. Demand a circuit list in the quote, not a vague “essentials included.”
EV chargers on backup?
Usually no for overnight AC charging — a 7.4 kW wallbox is a battery vacuum. Prefer solar-matched daytime charging or grid off-peak on TOU tariffs — charge EV from solar, TOU / prepaid + EV, EV load management.
Medical and work-from-home loads
Declare CPAP, oxygen concentrators, refrigerated medicine and always-on work routers in writing. Undersized “lights only” backups fail families. If medical loads are critical, discuss redundancy (second battery module, generator interlock) rather than optimistic marketing runtime.
Quote checklist
- Written list of essential circuits with estimated watts.
- Inverter backup power rating continuous and surge.
- Usable battery kWh and recommended DoD for daily vs emergency use.
- What happens to non-essentials during shedding (stay off / generator).
- Whether PV still charges the pack while islanded.
SA caveats
Stage schedules change; design for the worst stage you actually experience locally, not a national average. Whole-home transfer switches look neat in demos and brutal on payback for 5–10 kWh packs. Educational only — your electrician sizes conductors and protection to SANS rules.
Quick FAQ
Can I move the geyser later? Often yes, but re-balancing may need a return visit and CoC update.
Do non-essentials still get cheap solar by day? Yes — they can run from PV/grid while the grid is up; they just drop in shedding.
Is UPS mode the same? Hybrid backup ports and cheap socket UPS units are different safety stories — prefer a designed hybrid essential board.
Labeling and family habits
The best essential board fails if teenagers plug a heater into a “lights” circuit. Label sockets, brief the household, and consider dedicated essential plug colours. During long Stage 6 evenings, move laundry and dishwashing to grid-up windows instead of arguing with the inverter’s overload alarm.
Water heating strategies that protect the pack
Move geysers off backup and onto daytime PV timers, heat pumps, or solar thermal where appropriate. A heat pump on non-essential still cuts the monthly kWh line dramatically compared with a 3 kW element — water heating guide. That is bill savings even when shedding resilience stays “fridge and lights.”
Staged expansion
Start conservative: lights, ICT, fridge, security. After a month of runtime data, decide whether a second battery module justifies adding the fibre ONT room aircon or a freezer in the garage. Expanding essentials without expanding kWh is how runtime collapses.
Generator pairing
If a generator covers non-essentials or recharges the pack, document the interlock and fuel plan. Do not rely on manual changeover improvisation at 20:00 in the dark — ATS. Noise bylaws in estates may limit generator use even when the battery is empty.
Worked budget thought-experiment
Compare Quote A: 10 kWh + tight essentials. Quote B: 15 kWh + geyser on backup. If Quote B costs R25 000 more and only adds comfort rare evenings, price those evenings against a thermos and a daytime geyser boost from PV. Savings-led design usually picks A and a heat-pump plan.
Measuring before you split
A week of plug-level or CT-level logging beats guessing. Clamp meters on geyser and stove circuits show why those loads destroy runtime. Share the log with every bidder so essentials lists converge. If logging is impossible, use conservative nameplate estimates and accept that the first month is a calibration exercise.
Three-phase essentials boards
On three-phase hybrids, balance essential circuits across phases where the OEM requires it. A single-phase essentials board hanging off one leg of a three-phase hybrid can hit per-phase limits early — single vs three-phase. Have the designer show per-phase backup budgets on the drawing.
Medical declarations belong in the contract annex, not only in a WhatsApp note, so the commissioning tech does not deprioritise a critical circuit.
Seasonal rethink
Winter Highveld evenings and humid KZN summers change which circuits feel “essential.” Revisit the list each season: bathroom extractor fans, dehumidifiers, or extra lighting may rotate. Changing breaker assignments should be done by a registered person with CoC updates when the work warrants it — not by informal jumper experiments.
Track runtime from the inverter app across a month of real shedding. If essentials die at 40% SoC every time, you are overloaded — shed a circuit or add kWh before blaming the battery brand.