EV charging
How does EV charger load management work with load shedding in South Africa?
A wallbox without load management will fight your geyser and oven for amps — and during load shedding a grid-tied charger simply stops unless your hybrid and battery were sized to feed it (most homes should not). Dynamic load management (CT or meter) throttles the EV so the main breaker survives; shedding strategy is about schedules and backup priorities, not hoping the car becomes a free UPS.
Updated 26 October 2026 · Illustrative ranges — not a formal quote or legal advice.
Answer first: Load management keeps your wallbox from stealing amps the geyser, stove and pool pump already claimed. Load shedding is a separate problem: when the municipal feeder dies, a normal grid-tied charger dies with it. Confusing the two is how households either trip the main breaker every evening or drain a precious battery pack into a parked car during Stage 6.
How dynamic load management works
A current transformer (CT) or energy meter on the main incoming tails tells the wallbox how much headroom remains under the main breaker. When the house load rises, the charger throttles from (say) 32 A toward 6 A or pauses. When the house quiets, charging resumes. This is table-stakes on serious SA quotes for 60 A single-phase supplies — chooser, power levels.
Static limits vs dynamic
A static 20 A software cap is better than nothing but wastes overnight capacity. Dynamic control recovers kilometres without forcing you to babysit the app every time someone boils a kettle. Multi-bay estates need hierarchical load balancing (site limit → bay limit) — estates, fleets.
What happens in load shedding
- Grid-tied wallbox on non-essential bus: stops until power returns.
- Wallbox on hybrid essential/backup bus: can continue only if inverter backup rating and battery usable kWh cover EV + house essentials.
- Public DC with on-site BESS: some sites stay up (e.g. battery-backed pins); confirm live status in the app.
Most suburban hybrids are sized for lights, Wi-Fi, fridge and selected plugs — not a continuous 7 kW car. Feeding the EV during Stage 6 can empty a 10 kWh pack in under two hours before the fridge loses the fight — Stage 6 sizing, essential loads.
Scheduling around shedding
Use EskomSePush / municipal apps plus charger schedules: prefer windows after overnight recovery and before morning departure; pause during announced stages; pre-condition the cabin while still on grid when possible. TOU tariffs add another layer — charging into a peak evening block can cost more than a midday solar session — TOU / prepaid, cost to charge.
Solar surplus charging
Solar-aware modes that follow PV surplus are a form of load management tied to generation rather than the main breaker. They protect export economics (metro credits ~108–185 c/kWh incl. vs multi-rand import) and reduce evening grid draw — solar EV charging.
DB and breaker realities
Load management cannot invent amps that a undersized main or ageing DB cannot deliver. If the board is full or the tails are marginal, budget a DB rework before the wallbox — DB upgrade, wiring & CoC. Registered electrician required for fixed work — DIY limits.
Fleet and workplace notes
Diversity factors matter: ten 7 kW bays rarely need 70 kW of simultaneous supply if cars dwell all day. OCPP backends and site controllers enforce caps. Without them, the first rainy cold Monday trips the transformer.
Quote checklist
- CT / meter included and installation location shown on the single-line.
- Configured site limit matching the main breaker with margin.
- Behaviour during grid loss documented (stop vs backup).
- App schedule + solar mode demonstrated at handover.
- CoC covers the new circuit.
SA caveats
Shedding stages and municipal schedules change. Battery-backed public pins are site-specific. Educational only.
Quick FAQ
Will load management save money? Indirectly — it prevents trips and lets you use cheaper overnight or solar windows safely.
Can V2H power the house instead? Not a mainstream residential pathway in SA yet — V2H / V2G.
Do portable chargers load-manage? Usually no meaningful dynamic control — another reason they are backup tools.
Worked amp example (single-phase 60 A)
Main breaker 60 A ≈ 13.8 kW at 230 V. Geyser 3 kW + oven 2.5 kW + other house 2 kW leaves ~6 kW headroom — enough for a throttled EV, not a locked 7.4 kW charge plus cooking. Dynamic control might run the car at 16–20 A during dinner and climb back to 32 A after 21:00. Without it, the main trips and everyone loses lights — including the Wi-Fi you need for the shedding schedule app.
Hybrid backup maths people skip
A 5 kW hybrid backup rating is not the same as 5 kW free for the car. Surge loads (fridges, pumps) and continuous EV draw stack. If the inverter continuous backup is 5 kW and essentials already need 1.5 kW, the EV cannot take 7 kW from that bus. Either keep the wallbox on the non-essential grid-tied side or upsizing inverter and battery deliberately — inverter size, solar + EV.
Communication failures
Wi-Fi dropouts should fail safe (throttle or pause), not slam to max amps. Ask the installer to demonstrate behaviour when the CT lead is disconnected. Mid-shed firmware updates are a bad idea; schedule maintenance on stable grid days.
Workplace diversity in one paragraph
Twenty staff bays with 7 kW nameplates might be engineered for 40–60% diversity if cars arrive staggered. Without a site controller, everyone plugs in at 07:45 after a cold morning and the transformer complains. Load management is how employers avoid paying for a supply upgrade they only need thirty minutes a day.
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 use last year’s crisis tariff increases 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
South African buyers often flip the order: they buy for Stage 6 anxiety and only later discover the bill maths. Flip it back. 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 a oversized grey-import stack that never finishes SSEG.
Documents to keep in one folder
CoC, inverter NRS certificate, battery warranty PDF, SSEG approval, as-built diagrams, serial numbers, and app login details. When you sell the house or claim warranty, this folder is worth more than another brochure. Photograph the DB before and after works. Store cloud copies — paper in a garage floods.
Common salesperson scripts to challenge
“Export will pay for the system,” “batteries are optional fluff,” “you don’t need municipal registration,” “this inverter is the same as the NRS one,” “V2G will make you money next year.” Each script has a grain of truth wrapped around a costly exaggeration. Ask for the primary metro PDF or certificate page, not a WhatsApp forward.