Backup · 2026-02-20
Load Shedding Backup Sizing Guide for SA Homes
How to size hybrid inverter backup power and battery kWh for South African load shedding — critical loads first.
Backup fails when people buy “a 5kWh battery” without listing what must stay on. Use this sizing sketch before you compare quotes.
Step 1 — Critical load list
Lights on used circuits, Wi-Fi/ONT, fridge/freezer, modem, selected work plugs, maybe garage motor. Decide deliberately about geyser, stove, aircon and pool — these dominate energy.
Step 2 — Estimate watts and hours
Add continuous watts of essentials. Multiply by desired backup hours (e.g. 2.5–4 hours for many Stage patterns). Convert Wh to kWh and add 20–40% margin for inefficiency and ageing.
Step 3 — Match inverter backup rating
Battery kWh is energy; inverter backup kW is power. A large battery behind an undersized backup output still trips when the kettle and fridge start together on the backup board.
Step 4 — Solar recharge between slots
Daytime PV recharge between load-shedding windows is what makes multi-day resilience possible. Backup-only systems without solar deplete faster during clustered stages.
See also: Load shedding guide · Batteries & BESS